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WSL2-Linux-Kernel
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WSL2-Linux-Kernel/fs/namei.c

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59 KiB
C
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/*
* linux/fs/namei.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*/
/*
* Some corrections by tytso.
*/
/* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
* lookup logic.
*/
/* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
*/
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/quotaops.h>
#include <linux/pagemap.h>
#include <linux/dnotify.h>
#include <linux/smp_lock.h>
#include <linux/personality.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/mount.h>
#include <linux/audit.h>
#include <asm/namei.h>
#include <asm/uaccess.h>
#define ACC_MODE(x) ("\000\004\002\006"[(x)&O_ACCMODE])
/* [Feb-1997 T. Schoebel-Theuer]
* Fundamental changes in the pathname lookup mechanisms (namei)
* were necessary because of omirr. The reason is that omirr needs
* to know the _real_ pathname, not the user-supplied one, in case
* of symlinks (and also when transname replacements occur).
*
* The new code replaces the old recursive symlink resolution with
* an iterative one (in case of non-nested symlink chains). It does
* this with calls to <fs>_follow_link().
* As a side effect, dir_namei(), _namei() and follow_link() are now
* replaced with a single function lookup_dentry() that can handle all
* the special cases of the former code.
*
* With the new dcache, the pathname is stored at each inode, at least as
* long as the refcount of the inode is positive. As a side effect, the
* size of the dcache depends on the inode cache and thus is dynamic.
*
* [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
* resolution to correspond with current state of the code.
*
* Note that the symlink resolution is not *completely* iterative.
* There is still a significant amount of tail- and mid- recursion in
* the algorithm. Also, note that <fs>_readlink() is not used in
* lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
* may return different results than <fs>_follow_link(). Many virtual
* filesystems (including /proc) exhibit this behavior.
*/
/* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
* New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
* and the name already exists in form of a symlink, try to create the new
* name indicated by the symlink. The old code always complained that the
* name already exists, due to not following the symlink even if its target
* is nonexistent. The new semantics affects also mknod() and link() when
* the name is a symlink pointing to a non-existant name.
*
* I don't know which semantics is the right one, since I have no access
* to standards. But I found by trial that HP-UX 9.0 has the full "new"
* semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
* "old" one. Personally, I think the new semantics is much more logical.
* Note that "ln old new" where "new" is a symlink pointing to a non-existing
* file does succeed in both HP-UX and SunOs, but not in Solaris
* and in the old Linux semantics.
*/
/* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
* semantics. See the comments in "open_namei" and "do_link" below.
*
* [10-Sep-98 Alan Modra] Another symlink change.
*/
/* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
* inside the path - always follow.
* in the last component in creation/removal/renaming - never follow.
* if LOOKUP_FOLLOW passed - follow.
* if the pathname has trailing slashes - follow.
* otherwise - don't follow.
* (applied in that order).
*
* [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
* restored for 2.4. This is the last surviving part of old 4.2BSD bug.
* During the 2.4 we need to fix the userland stuff depending on it -
* hopefully we will be able to get rid of that wart in 2.5. So far only
* XEmacs seems to be relying on it...
*/
/*
* [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
* implemented. Let's see if raised priority of ->s_vfs_rename_sem gives
* any extra contention...
*/
/* In order to reduce some races, while at the same time doing additional
* checking and hopefully speeding things up, we copy filenames to the
* kernel data space before using them..
*
* POSIX.1 2.4: an empty pathname is invalid (ENOENT).
* PATH_MAX includes the nul terminator --RR.
*/
static inline int do_getname(const char __user *filename, char *page)
{
int retval;
unsigned long len = PATH_MAX;
if (!segment_eq(get_fs(), KERNEL_DS)) {
if ((unsigned long) filename >= TASK_SIZE)
return -EFAULT;
if (TASK_SIZE - (unsigned long) filename < PATH_MAX)
len = TASK_SIZE - (unsigned long) filename;
}
retval = strncpy_from_user(page, filename, len);
if (retval > 0) {
if (retval < len)
return 0;
return -ENAMETOOLONG;
} else if (!retval)
retval = -ENOENT;
return retval;
}
char * getname(const char __user * filename)
{
char *tmp, *result;
result = ERR_PTR(-ENOMEM);
tmp = __getname();
if (tmp) {
int retval = do_getname(filename, tmp);
result = tmp;
if (retval < 0) {
__putname(tmp);
result = ERR_PTR(retval);
}
}
audit_getname(result);
return result;
}
#ifdef CONFIG_AUDITSYSCALL
void putname(const char *name)
{
if (unlikely(current->audit_context))
audit_putname(name);
else
__putname(name);
}
EXPORT_SYMBOL(putname);
#endif
/**
* generic_permission - check for access rights on a Posix-like filesystem
* @inode: inode to check access rights for
* @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
* @check_acl: optional callback to check for Posix ACLs
*
* Used to check for read/write/execute permissions on a file.
* We use "fsuid" for this, letting us set arbitrary permissions
* for filesystem access without changing the "normal" uids which
* are used for other things..
*/
int generic_permission(struct inode *inode, int mask,
int (*check_acl)(struct inode *inode, int mask))
{
umode_t mode = inode->i_mode;
if (current->fsuid == inode->i_uid)
mode >>= 6;
else {
if (IS_POSIXACL(inode) && (mode & S_IRWXG) && check_acl) {
int error = check_acl(inode, mask);
if (error == -EACCES)
goto check_capabilities;
else if (error != -EAGAIN)
return error;
}
if (in_group_p(inode->i_gid))
mode >>= 3;
}
/*
* If the DACs are ok we don't need any capability check.
*/
if (((mode & mask & (MAY_READ|MAY_WRITE|MAY_EXEC)) == mask))
return 0;
check_capabilities:
/*
* Read/write DACs are always overridable.
* Executable DACs are overridable if at least one exec bit is set.
*/
if (!(mask & MAY_EXEC) ||
(inode->i_mode & S_IXUGO) || S_ISDIR(inode->i_mode))
if (capable(CAP_DAC_OVERRIDE))
return 0;
/*
* Searching includes executable on directories, else just read.
*/
if (mask == MAY_READ || (S_ISDIR(inode->i_mode) && !(mask & MAY_WRITE)))
if (capable(CAP_DAC_READ_SEARCH))
return 0;
return -EACCES;
}
int permission(struct inode *inode, int mask, struct nameidata *nd)
{
int retval, submask;
if (mask & MAY_WRITE) {
umode_t mode = inode->i_mode;
/*
* Nobody gets write access to a read-only fs.
*/
if (IS_RDONLY(inode) &&
(S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
return -EROFS;
/*
* Nobody gets write access to an immutable file.
*/
if (IS_IMMUTABLE(inode))
return -EACCES;
}
/* Ordinary permission routines do not understand MAY_APPEND. */
submask = mask & ~MAY_APPEND;
if (inode->i_op && inode->i_op->permission)
retval = inode->i_op->permission(inode, submask, nd);
else
retval = generic_permission(inode, submask, NULL);
if (retval)
return retval;
return security_inode_permission(inode, mask, nd);
}
/*
* get_write_access() gets write permission for a file.
* put_write_access() releases this write permission.
* This is used for regular files.
* We cannot support write (and maybe mmap read-write shared) accesses and
* MAP_DENYWRITE mmappings simultaneously. The i_writecount field of an inode
* can have the following values:
* 0: no writers, no VM_DENYWRITE mappings
* < 0: (-i_writecount) vm_area_structs with VM_DENYWRITE set exist
* > 0: (i_writecount) users are writing to the file.
*
* Normally we operate on that counter with atomic_{inc,dec} and it's safe
* except for the cases where we don't hold i_writecount yet. Then we need to
* use {get,deny}_write_access() - these functions check the sign and refuse
* to do the change if sign is wrong. Exclusion between them is provided by
* the inode->i_lock spinlock.
*/
int get_write_access(struct inode * inode)
{
spin_lock(&inode->i_lock);
if (atomic_read(&inode->i_writecount) < 0) {
spin_unlock(&inode->i_lock);
return -ETXTBSY;
}
atomic_inc(&inode->i_writecount);
spin_unlock(&inode->i_lock);
return 0;
}
int deny_write_access(struct file * file)
{
struct inode *inode = file->f_dentry->d_inode;
spin_lock(&inode->i_lock);
if (atomic_read(&inode->i_writecount) > 0) {
spin_unlock(&inode->i_lock);
return -ETXTBSY;
}
atomic_dec(&inode->i_writecount);
spin_unlock(&inode->i_lock);
return 0;
}
void path_release(struct nameidata *nd)
{
dput(nd->dentry);
mntput(nd->mnt);
}
/*
* umount() mustn't call path_release()/mntput() as that would clear
* mnt_expiry_mark
*/
void path_release_on_umount(struct nameidata *nd)
{
dput(nd->dentry);
_mntput(nd->mnt);
}
/*
* Internal lookup() using the new generic dcache.
* SMP-safe
*/
static struct dentry * cached_lookup(struct dentry * parent, struct qstr * name, struct nameidata *nd)
{
struct dentry * dentry = __d_lookup(parent, name);
/* lockess __d_lookup may fail due to concurrent d_move()
* in some unrelated directory, so try with d_lookup
*/
if (!dentry)
dentry = d_lookup(parent, name);
if (dentry && dentry->d_op && dentry->d_op->d_revalidate) {
if (!dentry->d_op->d_revalidate(dentry, nd) && !d_invalidate(dentry)) {
dput(dentry);
dentry = NULL;
}
}
return dentry;
}
/*
* Short-cut version of permission(), for calling by
* path_walk(), when dcache lock is held. Combines parts
* of permission() and generic_permission(), and tests ONLY for
* MAY_EXEC permission.
*
* If appropriate, check DAC only. If not appropriate, or
* short-cut DAC fails, then call permission() to do more
* complete permission check.
*/
static inline int exec_permission_lite(struct inode *inode,
struct nameidata *nd)
{
umode_t mode = inode->i_mode;
if (inode->i_op && inode->i_op->permission)
return -EAGAIN;
if (current->fsuid == inode->i_uid)
mode >>= 6;
else if (in_group_p(inode->i_gid))
mode >>= 3;
if (mode & MAY_EXEC)
goto ok;
if ((inode->i_mode & S_IXUGO) && capable(CAP_DAC_OVERRIDE))
goto ok;
if (S_ISDIR(inode->i_mode) && capable(CAP_DAC_OVERRIDE))
goto ok;
if (S_ISDIR(inode->i_mode) && capable(CAP_DAC_READ_SEARCH))
goto ok;
return -EACCES;
ok:
return security_inode_permission(inode, MAY_EXEC, nd);
}
/*
* This is called when everything else fails, and we actually have
* to go to the low-level filesystem to find out what we should do..
*
* We get the directory semaphore, and after getting that we also
* make sure that nobody added the entry to the dcache in the meantime..
* SMP-safe
*/
static struct dentry * real_lookup(struct dentry * parent, struct qstr * name, struct nameidata *nd)
{
struct dentry * result;
struct inode *dir = parent->d_inode;
down(&dir->i_sem);
/*
* First re-do the cached lookup just in case it was created
* while we waited for the directory semaphore..
*
* FIXME! This could use version numbering or similar to
* avoid unnecessary cache lookups.
*
* The "dcache_lock" is purely to protect the RCU list walker
* from concurrent renames at this point (we mustn't get false
* negatives from the RCU list walk here, unlike the optimistic
* fast walk).
*
* so doing d_lookup() (with seqlock), instead of lockfree __d_lookup
*/
result = d_lookup(parent, name);
if (!result) {
struct dentry * dentry = d_alloc(parent, name);
result = ERR_PTR(-ENOMEM);
if (dentry) {
result = dir->i_op->lookup(dir, dentry, nd);
if (result)
dput(dentry);
else
result = dentry;
}
up(&dir->i_sem);
return result;
}
/*
* Uhhuh! Nasty case: the cache was re-populated while
* we waited on the semaphore. Need to revalidate.
*/
up(&dir->i_sem);
if (result->d_op && result->d_op->d_revalidate) {
if (!result->d_op->d_revalidate(result, nd) && !d_invalidate(result)) {
dput(result);
result = ERR_PTR(-ENOENT);
}
}
return result;
}
static int __emul_lookup_dentry(const char *, struct nameidata *);
/* SMP-safe */
static inline int
walk_init_root(const char *name, struct nameidata *nd)
{
read_lock(&current->fs->lock);
if (current->fs->altroot && !(nd->flags & LOOKUP_NOALT)) {
nd->mnt = mntget(current->fs->altrootmnt);
nd->dentry = dget(current->fs->altroot);
read_unlock(&current->fs->lock);
if (__emul_lookup_dentry(name,nd))
return 0;
read_lock(&current->fs->lock);
}
nd->mnt = mntget(current->fs->rootmnt);
nd->dentry = dget(current->fs->root);
read_unlock(&current->fs->lock);
return 1;
}
static inline int __vfs_follow_link(struct nameidata *nd, const char *link)
{
int res = 0;
char *name;
if (IS_ERR(link))
goto fail;
if (*link == '/') {
path_release(nd);
if (!walk_init_root(link, nd))
/* weird __emul_prefix() stuff did it */
goto out;
}
res = link_path_walk(link, nd);
out:
if (nd->depth || res || nd->last_type!=LAST_NORM)
return res;
/*
* If it is an iterative symlinks resolution in open_namei() we
* have to copy the last component. And all that crap because of
* bloody create() on broken symlinks. Furrfu...
*/
name = __getname();
if (unlikely(!name)) {
path_release(nd);
return -ENOMEM;
}
strcpy(name, nd->last.name);
nd->last.name = name;
return 0;
fail:
path_release(nd);
return PTR_ERR(link);
}
static inline int __do_follow_link(struct dentry *dentry, struct nameidata *nd)
{
int error;
touch_atime(nd->mnt, dentry);
nd_set_link(nd, NULL);
error = dentry->d_inode->i_op->follow_link(dentry, nd);
if (!error) {
char *s = nd_get_link(nd);
if (s)
error = __vfs_follow_link(nd, s);
if (dentry->d_inode->i_op->put_link)
dentry->d_inode->i_op->put_link(dentry, nd);
}
return error;
}
/*
* This limits recursive symlink follows to 8, while
* limiting consecutive symlinks to 40.
*
* Without that kind of total limit, nasty chains of consecutive
* symlinks can cause almost arbitrarily long lookups.
*/
static inline int do_follow_link(struct dentry *dentry, struct nameidata *nd)
{
int err = -ELOOP;
if (current->link_count >= MAX_NESTED_LINKS)
goto loop;
if (current->total_link_count >= 40)
goto loop;
BUG_ON(nd->depth >= MAX_NESTED_LINKS);
cond_resched();
err = security_inode_follow_link(dentry, nd);
if (err)
goto loop;
current->link_count++;
current->total_link_count++;
nd->depth++;
err = __do_follow_link(dentry, nd);
current->link_count--;
nd->depth--;
return err;
loop:
path_release(nd);
return err;
}
int follow_up(struct vfsmount **mnt, struct dentry **dentry)
{
struct vfsmount *parent;
struct dentry *mountpoint;
spin_lock(&vfsmount_lock);
parent=(*mnt)->mnt_parent;
if (parent == *mnt) {
spin_unlock(&vfsmount_lock);
return 0;
}
mntget(parent);
mountpoint=dget((*mnt)->mnt_mountpoint);
spin_unlock(&vfsmount_lock);
dput(*dentry);
*dentry = mountpoint;
mntput(*mnt);
*mnt = parent;
return 1;
}
/* no need for dcache_lock, as serialization is taken care in
* namespace.c
*/
static int follow_mount(struct vfsmount **mnt, struct dentry **dentry)
{
int res = 0;
while (d_mountpoint(*dentry)) {
struct vfsmount *mounted = lookup_mnt(*mnt, *dentry);
if (!mounted)
break;
mntput(*mnt);
*mnt = mounted;
dput(*dentry);
*dentry = dget(mounted->mnt_root);
res = 1;
}
return res;
}
/* no need for dcache_lock, as serialization is taken care in
* namespace.c
*/
static inline int __follow_down(struct vfsmount **mnt, struct dentry **dentry)
{
struct vfsmount *mounted;
mounted = lookup_mnt(*mnt, *dentry);
if (mounted) {
mntput(*mnt);
*mnt = mounted;
dput(*dentry);
*dentry = dget(mounted->mnt_root);
return 1;
}
return 0;
}
int follow_down(struct vfsmount **mnt, struct dentry **dentry)
{
return __follow_down(mnt,dentry);
}
static inline void follow_dotdot(struct vfsmount **mnt, struct dentry **dentry)
{
while(1) {
struct vfsmount *parent;
struct dentry *old = *dentry;
read_lock(&current->fs->lock);
if (*dentry == current->fs->root &&
*mnt == current->fs->rootmnt) {
read_unlock(&current->fs->lock);
break;
}
read_unlock(&current->fs->lock);
spin_lock(&dcache_lock);
if (*dentry != (*mnt)->mnt_root) {
*dentry = dget((*dentry)->d_parent);
spin_unlock(&dcache_lock);
dput(old);
break;
}
spin_unlock(&dcache_lock);
spin_lock(&vfsmount_lock);
parent = (*mnt)->mnt_parent;
if (parent == *mnt) {
spin_unlock(&vfsmount_lock);
break;
}
mntget(parent);
*dentry = dget((*mnt)->mnt_mountpoint);
spin_unlock(&vfsmount_lock);
dput(old);
mntput(*mnt);
*mnt = parent;
}
follow_mount(mnt, dentry);
}
struct path {
struct vfsmount *mnt;
struct dentry *dentry;
};
/*
* It's more convoluted than I'd like it to be, but... it's still fairly
* small and for now I'd prefer to have fast path as straight as possible.
* It _is_ time-critical.
*/
static int do_lookup(struct nameidata *nd, struct qstr *name,
struct path *path)
{
struct vfsmount *mnt = nd->mnt;
struct dentry *dentry = __d_lookup(nd->dentry, name);
if (!dentry)
goto need_lookup;
if (dentry->d_op && dentry->d_op->d_revalidate)
goto need_revalidate;
done:
path->mnt = mnt;
path->dentry = dentry;
return 0;
need_lookup:
dentry = real_lookup(nd->dentry, name, nd);
if (IS_ERR(dentry))
goto fail;
goto done;
need_revalidate:
if (dentry->d_op->d_revalidate(dentry, nd))
goto done;
if (d_invalidate(dentry))
goto done;
dput(dentry);
goto need_lookup;
fail:
return PTR_ERR(dentry);
}
/*
* Name resolution.
*
* This is the basic name resolution function, turning a pathname
* into the final dentry.
*
* We expect 'base' to be positive and a directory.
*/
static fastcall int __link_path_walk(const char * name, struct nameidata *nd)
{
struct path next;
struct inode *inode;
int err;
unsigned int lookup_flags = nd->flags;
while (*name=='/')
name++;
if (!*name)
goto return_reval;
inode = nd->dentry->d_inode;
if (nd->depth)
lookup_flags = LOOKUP_FOLLOW;
/* At this point we know we have a real path component. */
for(;;) {
unsigned long hash;
struct qstr this;
unsigned int c;
err = exec_permission_lite(inode, nd);
if (err == -EAGAIN) {
err = permission(inode, MAY_EXEC, nd);
}
if (err)
break;
this.name = name;
c = *(const unsigned char *)name;
hash = init_name_hash();
do {
name++;
hash = partial_name_hash(c, hash);
c = *(const unsigned char *)name;
} while (c && (c != '/'));
this.len = name - (const char *) this.name;
this.hash = end_name_hash(hash);
/* remove trailing slashes? */
if (!c)
goto last_component;
while (*++name == '/');
if (!*name)
goto last_with_slashes;
/*
* "." and ".." are special - ".." especially so because it has
* to be able to know about the current root directory and
* parent relationships.
*/
if (this.name[0] == '.') switch (this.len) {
default:
break;
case 2:
if (this.name[1] != '.')
break;
follow_dotdot(&nd->mnt, &nd->dentry);
inode = nd->dentry->d_inode;
/* fallthrough */
case 1:
continue;
}
/*
* See if the low-level filesystem might want
* to use its own hash..
*/
if (nd->dentry->d_op && nd->dentry->d_op->d_hash) {
err = nd->dentry->d_op->d_hash(nd->dentry, &this);
if (err < 0)
break;
}
nd->flags |= LOOKUP_CONTINUE;
/* This does the actual lookups.. */
err = do_lookup(nd, &this, &next);
if (err)
break;
/* Check mountpoints.. */
follow_mount(&next.mnt, &next.dentry);
err = -ENOENT;
inode = next.dentry->d_inode;
if (!inode)
goto out_dput;
err = -ENOTDIR;
if (!inode->i_op)
goto out_dput;
if (inode->i_op->follow_link) {
mntget(next.mnt);
err = do_follow_link(next.dentry, nd);
dput(next.dentry);
mntput(next.mnt);
if (err)
goto return_err;
err = -ENOENT;
inode = nd->dentry->d_inode;
if (!inode)
break;
err = -ENOTDIR;
if (!inode->i_op)
break;
} else {
dput(nd->dentry);
nd->mnt = next.mnt;
nd->dentry = next.dentry;
}
err = -ENOTDIR;
if (!inode->i_op->lookup)
break;
continue;
/* here ends the main loop */
last_with_slashes:
lookup_flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
last_component:
nd->flags &= ~LOOKUP_CONTINUE;
if (lookup_flags & LOOKUP_PARENT)
goto lookup_parent;
if (this.name[0] == '.') switch (this.len) {
default:
break;
case 2:
if (this.name[1] != '.')
break;
follow_dotdot(&nd->mnt, &nd->dentry);
inode = nd->dentry->d_inode;
/* fallthrough */
case 1:
goto return_reval;
}
if (nd->dentry->d_op && nd->dentry->d_op->d_hash) {
err = nd->dentry->d_op->d_hash(nd->dentry, &this);
if (err < 0)
break;
}
err = do_lookup(nd, &this, &next);
if (err)
break;
follow_mount(&next.mnt, &next.dentry);
inode = next.dentry->d_inode;
if ((lookup_flags & LOOKUP_FOLLOW)
&& inode && inode->i_op && inode->i_op->follow_link) {
mntget(next.mnt);
err = do_follow_link(next.dentry, nd);
dput(next.dentry);
mntput(next.mnt);
if (err)
goto return_err;
inode = nd->dentry->d_inode;
} else {
dput(nd->dentry);
nd->mnt = next.mnt;
nd->dentry = next.dentry;
}
err = -ENOENT;
if (!inode)
break;
if (lookup_flags & LOOKUP_DIRECTORY) {
err = -ENOTDIR;
if (!inode->i_op || !inode->i_op->lookup)
break;
}
goto return_base;
lookup_parent:
nd->last = this;
nd->last_type = LAST_NORM;
if (this.name[0] != '.')
goto return_base;
if (this.len == 1)
nd->last_type = LAST_DOT;
else if (this.len == 2 && this.name[1] == '.')
nd->last_type = LAST_DOTDOT;
else
goto return_base;
return_reval:
/*
* We bypassed the ordinary revalidation routines.
* We may need to check the cached dentry for staleness.
*/
if (nd->dentry && nd->dentry->d_sb &&
(nd->dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)) {
err = -ESTALE;
/* Note: we do not d_invalidate() */
if (!nd->dentry->d_op->d_revalidate(nd->dentry, nd))
break;
}
return_base:
return 0;
out_dput:
dput(next.dentry);
break;
}
path_release(nd);
return_err:
return err;
}
/*
* Wrapper to retry pathname resolution whenever the underlying
* file system returns an ESTALE.
*
* Retry the whole path once, forcing real lookup requests
* instead of relying on the dcache.
*/
int fastcall link_path_walk(const char *name, struct nameidata *nd)
{
struct nameidata save = *nd;
int result;
/* make sure the stuff we saved doesn't go away */
dget(save.dentry);
mntget(save.mnt);
result = __link_path_walk(name, nd);
if (result == -ESTALE) {
*nd = save;
dget(nd->dentry);
mntget(nd->mnt);
nd->flags |= LOOKUP_REVAL;
result = __link_path_walk(name, nd);
}
dput(save.dentry);
mntput(save.mnt);
return result;
}
int fastcall path_walk(const char * name, struct nameidata *nd)
{
current->total_link_count = 0;
return link_path_walk(name, nd);
}
/* SMP-safe */
/* returns 1 if everything is done */
static int __emul_lookup_dentry(const char *name, struct nameidata *nd)
{
if (path_walk(name, nd))
return 0; /* something went wrong... */
if (!nd->dentry->d_inode || S_ISDIR(nd->dentry->d_inode->i_mode)) {
struct dentry *old_dentry = nd->dentry;
struct vfsmount *old_mnt = nd->mnt;
struct qstr last = nd->last;
int last_type = nd->last_type;
/*
* NAME was not found in alternate root or it's a directory. Try to find
* it in the normal root:
*/
nd->last_type = LAST_ROOT;
read_lock(&current->fs->lock);
nd->mnt = mntget(current->fs->rootmnt);
nd->dentry = dget(current->fs->root);
read_unlock(&current->fs->lock);
if (path_walk(name, nd) == 0) {
if (nd->dentry->d_inode) {
dput(old_dentry);
mntput(old_mnt);
return 1;
}
path_release(nd);
}
nd->dentry = old_dentry;
nd->mnt = old_mnt;
nd->last = last;
nd->last_type = last_type;
}
return 1;
}
void set_fs_altroot(void)
{
char *emul = __emul_prefix();
struct nameidata nd;
struct vfsmount *mnt = NULL, *oldmnt;
struct dentry *dentry = NULL, *olddentry;
int err;
if (!emul)
goto set_it;
err = path_lookup(emul, LOOKUP_FOLLOW|LOOKUP_DIRECTORY|LOOKUP_NOALT, &nd);
if (!err) {
mnt = nd.mnt;
dentry = nd.dentry;
}
set_it:
write_lock(&current->fs->lock);
oldmnt = current->fs->altrootmnt;
olddentry = current->fs->altroot;
current->fs->altrootmnt = mnt;
current->fs->altroot = dentry;
write_unlock(&current->fs->lock);
if (olddentry) {
dput(olddentry);
mntput(oldmnt);
}
}
int fastcall path_lookup(const char *name, unsigned int flags, struct nameidata *nd)
{
int retval;
nd->last_type = LAST_ROOT; /* if there are only slashes... */
nd->flags = flags;
nd->depth = 0;
read_lock(&current->fs->lock);
if (*name=='/') {
if (current->fs->altroot && !(nd->flags & LOOKUP_NOALT)) {
nd->mnt = mntget(current->fs->altrootmnt);
nd->dentry = dget(current->fs->altroot);
read_unlock(&current->fs->lock);
if (__emul_lookup_dentry(name,nd))
return 0;
read_lock(&current->fs->lock);
}
nd->mnt = mntget(current->fs->rootmnt);
nd->dentry = dget(current->fs->root);
} else {
nd->mnt = mntget(current->fs->pwdmnt);
nd->dentry = dget(current->fs->pwd);
}
read_unlock(&current->fs->lock);
current->total_link_count = 0;
retval = link_path_walk(name, nd);
if (unlikely(current->audit_context
&& nd && nd->dentry && nd->dentry->d_inode))
audit_inode(name, nd->dentry->d_inode);
return retval;
}
/*
* Restricted form of lookup. Doesn't follow links, single-component only,
* needs parent already locked. Doesn't follow mounts.
* SMP-safe.
*/
static struct dentry * __lookup_hash(struct qstr *name, struct dentry * base, struct nameidata *nd)
{
struct dentry * dentry;
struct inode *inode;
int err;
inode = base->d_inode;
err = permission(inode, MAY_EXEC, nd);
dentry = ERR_PTR(err);
if (err)
goto out;
/*
* See if the low-level filesystem might want
* to use its own hash..
*/
if (base->d_op && base->d_op->d_hash) {
err = base->d_op->d_hash(base, name);
dentry = ERR_PTR(err);
if (err < 0)
goto out;
}
dentry = cached_lookup(base, name, nd);
if (!dentry) {
struct dentry *new = d_alloc(base, name);
dentry = ERR_PTR(-ENOMEM);
if (!new)
goto out;
dentry = inode->i_op->lookup(inode, new, nd);
if (!dentry)
dentry = new;
else
dput(new);
}
out:
return dentry;
}
struct dentry * lookup_hash(struct qstr *name, struct dentry * base)
{
return __lookup_hash(name, base, NULL);
}
/* SMP-safe */
struct dentry * lookup_one_len(const char * name, struct dentry * base, int len)
{
unsigned long hash;
struct qstr this;
unsigned int c;
this.name = name;
this.len = len;
if (!len)
goto access;
hash = init_name_hash();
while (len--) {
c = *(const unsigned char *)name++;
if (c == '/' || c == '\0')
goto access;
hash = partial_name_hash(c, hash);
}
this.hash = end_name_hash(hash);
return lookup_hash(&this, base);
access:
return ERR_PTR(-EACCES);
}
/*
* namei()
*
* is used by most simple commands to get the inode of a specified name.
* Open, link etc use their own routines, but this is enough for things
* like 'chmod' etc.
*
* namei exists in two versions: namei/lnamei. The only difference is
* that namei follows links, while lnamei does not.
* SMP-safe
*/
int fastcall __user_walk(const char __user *name, unsigned flags, struct nameidata *nd)
{
char *tmp = getname(name);
int err = PTR_ERR(tmp);
if (!IS_ERR(tmp)) {
err = path_lookup(tmp, flags, nd);
putname(tmp);
}
return err;
}
/*
* It's inline, so penalty for filesystems that don't use sticky bit is
* minimal.
*/
static inline int check_sticky(struct inode *dir, struct inode *inode)
{
if (!(dir->i_mode & S_ISVTX))
return 0;
if (inode->i_uid == current->fsuid)
return 0;
if (dir->i_uid == current->fsuid)
return 0;
return !capable(CAP_FOWNER);
}
/*
* Check whether we can remove a link victim from directory dir, check
* whether the type of victim is right.
* 1. We can't do it if dir is read-only (done in permission())
* 2. We should have write and exec permissions on dir
* 3. We can't remove anything from append-only dir
* 4. We can't do anything with immutable dir (done in permission())
* 5. If the sticky bit on dir is set we should either
* a. be owner of dir, or
* b. be owner of victim, or
* c. have CAP_FOWNER capability
* 6. If the victim is append-only or immutable we can't do antyhing with
* links pointing to it.
* 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
* 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
* 9. We can't remove a root or mountpoint.
* 10. We don't allow removal of NFS sillyrenamed files; it's handled by
* nfs_async_unlink().
*/
static inline int may_delete(struct inode *dir,struct dentry *victim,int isdir)
{
int error;
if (!victim->d_inode)
return -ENOENT;
BUG_ON(victim->d_parent->d_inode != dir);
error = permission(dir,MAY_WRITE | MAY_EXEC, NULL);
if (error)
return error;
if (IS_APPEND(dir))
return -EPERM;
if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
IS_IMMUTABLE(victim->d_inode))
return -EPERM;
if (isdir) {
if (!S_ISDIR(victim->d_inode->i_mode))
return -ENOTDIR;
if (IS_ROOT(victim))
return -EBUSY;
} else if (S_ISDIR(victim->d_inode->i_mode))
return -EISDIR;
if (IS_DEADDIR(dir))
return -ENOENT;
if (victim->d_flags & DCACHE_NFSFS_RENAMED)
return -EBUSY;
return 0;
}
/* Check whether we can create an object with dentry child in directory
* dir.
* 1. We can't do it if child already exists (open has special treatment for
* this case, but since we are inlined it's OK)
* 2. We can't do it if dir is read-only (done in permission())
* 3. We should have write and exec permissions on dir
* 4. We can't do it if dir is immutable (done in permission())
*/
static inline int may_create(struct inode *dir, struct dentry *child,
struct nameidata *nd)
{
if (child->d_inode)
return -EEXIST;
if (IS_DEADDIR(dir))
return -ENOENT;
return permission(dir,MAY_WRITE | MAY_EXEC, nd);
}
/*
* Special case: O_CREAT|O_EXCL implies O_NOFOLLOW for security
* reasons.
*
* O_DIRECTORY translates into forcing a directory lookup.
*/
static inline int lookup_flags(unsigned int f)
{
unsigned long retval = LOOKUP_FOLLOW;
if (f & O_NOFOLLOW)
retval &= ~LOOKUP_FOLLOW;
if ((f & (O_CREAT|O_EXCL)) == (O_CREAT|O_EXCL))
retval &= ~LOOKUP_FOLLOW;
if (f & O_DIRECTORY)
retval |= LOOKUP_DIRECTORY;
return retval;
}
/*
* p1 and p2 should be directories on the same fs.
*/
struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
{
struct dentry *p;
if (p1 == p2) {
down(&p1->d_inode->i_sem);
return NULL;
}
down(&p1->d_inode->i_sb->s_vfs_rename_sem);
for (p = p1; p->d_parent != p; p = p->d_parent) {
if (p->d_parent == p2) {
down(&p2->d_inode->i_sem);
down(&p1->d_inode->i_sem);
return p;
}
}
for (p = p2; p->d_parent != p; p = p->d_parent) {
if (p->d_parent == p1) {
down(&p1->d_inode->i_sem);
down(&p2->d_inode->i_sem);
return p;
}
}
down(&p1->d_inode->i_sem);
down(&p2->d_inode->i_sem);
return NULL;
}
void unlock_rename(struct dentry *p1, struct dentry *p2)
{
up(&p1->d_inode->i_sem);
if (p1 != p2) {
up(&p2->d_inode->i_sem);
up(&p1->d_inode->i_sb->s_vfs_rename_sem);
}
}
int vfs_create(struct inode *dir, struct dentry *dentry, int mode,
struct nameidata *nd)
{
int error = may_create(dir, dentry, nd);
if (error)
return error;
if (!dir->i_op || !dir->i_op->create)
return -EACCES; /* shouldn't it be ENOSYS? */
mode &= S_IALLUGO;
mode |= S_IFREG;
error = security_inode_create(dir, dentry, mode);
if (error)
return error;
DQUOT_INIT(dir);
error = dir->i_op->create(dir, dentry, mode, nd);
if (!error) {
inode_dir_notify(dir, DN_CREATE);
security_inode_post_create(dir, dentry, mode);
}
return error;
}
int may_open(struct nameidata *nd, int acc_mode, int flag)
{
struct dentry *dentry = nd->dentry;
struct inode *inode = dentry->d_inode;
int error;
if (!inode)
return -ENOENT;
if (S_ISLNK(inode->i_mode))
return -ELOOP;
if (S_ISDIR(inode->i_mode) && (flag & FMODE_WRITE))
return -EISDIR;
error = permission(inode, acc_mode, nd);
if (error)
return error;
/*
* FIFO's, sockets and device files are special: they don't
* actually live on the filesystem itself, and as such you
* can write to them even if the filesystem is read-only.
*/
if (S_ISFIFO(inode->i_mode) || S_ISSOCK(inode->i_mode)) {
flag &= ~O_TRUNC;
} else if (S_ISBLK(inode->i_mode) || S_ISCHR(inode->i_mode)) {
if (nd->mnt->mnt_flags & MNT_NODEV)
return -EACCES;
flag &= ~O_TRUNC;
} else if (IS_RDONLY(inode) && (flag & FMODE_WRITE))
return -EROFS;
/*
* An append-only file must be opened in append mode for writing.
*/
if (IS_APPEND(inode)) {
if ((flag & FMODE_WRITE) && !(flag & O_APPEND))
return -EPERM;
if (flag & O_TRUNC)
return -EPERM;
}
/* O_NOATIME can only be set by the owner or superuser */
if (flag & O_NOATIME)
if (current->fsuid != inode->i_uid && !capable(CAP_FOWNER))
return -EPERM;
/*
* Ensure there are no outstanding leases on the file.
*/
error = break_lease(inode, flag);
if (error)
return error;
if (flag & O_TRUNC) {
error = get_write_access(inode);
if (error)
return error;
/*
* Refuse to truncate files with mandatory locks held on them.
*/
error = locks_verify_locked(inode);
if (!error) {
DQUOT_INIT(inode);
error = do_truncate(dentry, 0);
}
put_write_access(inode);
if (error)
return error;
} else
if (flag & FMODE_WRITE)
DQUOT_INIT(inode);
return 0;
}
/*
* open_namei()
*
* namei for open - this is in fact almost the whole open-routine.
*
* Note that the low bits of "flag" aren't the same as in the open
* system call - they are 00 - no permissions needed
* 01 - read permission needed
* 10 - write permission needed
* 11 - read/write permissions needed
* which is a lot more logical, and also allows the "no perm" needed
* for symlinks (where the permissions are checked later).
* SMP-safe
*/
int open_namei(const char * pathname, int flag, int mode, struct nameidata *nd)
{
int acc_mode, error = 0;
struct dentry *dentry;
struct dentry *dir;
int count = 0;
acc_mode = ACC_MODE(flag);
/* Allow the LSM permission hook to distinguish append
access from general write access. */
if (flag & O_APPEND)
acc_mode |= MAY_APPEND;
/* Fill in the open() intent data */
nd->intent.open.flags = flag;
nd->intent.open.create_mode = mode;
/*
* The simplest case - just a plain lookup.
*/
if (!(flag & O_CREAT)) {
error = path_lookup(pathname, lookup_flags(flag)|LOOKUP_OPEN, nd);
if (error)
return error;
goto ok;
}
/*
* Create - we need to know the parent.
*/
error = path_lookup(pathname, LOOKUP_PARENT|LOOKUP_OPEN|LOOKUP_CREATE, nd);
if (error)
return error;
/*
* We have the parent and last component. First of all, check
* that we are not asked to creat(2) an obvious directory - that
* will not do.
*/
error = -EISDIR;
if (nd->last_type != LAST_NORM || nd->last.name[nd->last.len])
goto exit;
dir = nd->dentry;
nd->flags &= ~LOOKUP_PARENT;
down(&dir->d_inode->i_sem);
dentry = __lookup_hash(&nd->last, nd->dentry, nd);
do_last:
error = PTR_ERR(dentry);
if (IS_ERR(dentry)) {
up(&dir->d_inode->i_sem);
goto exit;
}
/* Negative dentry, just create the file */
if (!dentry->d_inode) {
if (!IS_POSIXACL(dir->d_inode))
mode &= ~current->fs->umask;
error = vfs_create(dir->d_inode, dentry, mode, nd);
up(&dir->d_inode->i_sem);
dput(nd->dentry);
nd->dentry = dentry;
if (error)
goto exit;
/* Don't check for write permission, don't truncate */
acc_mode = 0;
flag &= ~O_TRUNC;
goto ok;
}
/*
* It already exists.
*/
up(&dir->d_inode->i_sem);
error = -EEXIST;
if (flag & O_EXCL)
goto exit_dput;
if (d_mountpoint(dentry)) {
error = -ELOOP;
if (flag & O_NOFOLLOW)
goto exit_dput;
while (__follow_down(&nd->mnt,&dentry) && d_mountpoint(dentry));
}
error = -ENOENT;
if (!dentry->d_inode)
goto exit_dput;
if (dentry->d_inode->i_op && dentry->d_inode->i_op->follow_link)
goto do_link;
dput(nd->dentry);
nd->dentry = dentry;
error = -EISDIR;
if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode))
goto exit;
ok:
error = may_open(nd, acc_mode, flag);
if (error)
goto exit;
return 0;
exit_dput:
dput(dentry);
exit:
path_release(nd);
return error;
do_link:
error = -ELOOP;
if (flag & O_NOFOLLOW)
goto exit_dput;
/*
* This is subtle. Instead of calling do_follow_link() we do the
* thing by hands. The reason is that this way we have zero link_count
* and path_walk() (called from ->follow_link) honoring LOOKUP_PARENT.
* After that we have the parent and last component, i.e.
* we are in the same situation as after the first path_walk().
* Well, almost - if the last component is normal we get its copy
* stored in nd->last.name and we will have to putname() it when we
* are done. Procfs-like symlinks just set LAST_BIND.
*/
nd->flags |= LOOKUP_PARENT;
error = security_inode_follow_link(dentry, nd);
if (error)
goto exit_dput;
error = __do_follow_link(dentry, nd);
dput(dentry);
if (error)
return error;
nd->flags &= ~LOOKUP_PARENT;
if (nd->last_type == LAST_BIND) {
dentry = nd->dentry;
goto ok;
}
error = -EISDIR;
if (nd->last_type != LAST_NORM)
goto exit;
if (nd->last.name[nd->last.len]) {
putname(nd->last.name);
goto exit;
}
error = -ELOOP;
if (count++==32) {
putname(nd->last.name);
goto exit;
}
dir = nd->dentry;
down(&dir->d_inode->i_sem);
dentry = __lookup_hash(&nd->last, nd->dentry, nd);
putname(nd->last.name);
goto do_last;
}
/**
* lookup_create - lookup a dentry, creating it if it doesn't exist
* @nd: nameidata info
* @is_dir: directory flag
*
* Simple function to lookup and return a dentry and create it
* if it doesn't exist. Is SMP-safe.
*/
struct dentry *lookup_create(struct nameidata *nd, int is_dir)
{
struct dentry *dentry;
down(&nd->dentry->d_inode->i_sem);
dentry = ERR_PTR(-EEXIST);
if (nd->last_type != LAST_NORM)
goto fail;
nd->flags &= ~LOOKUP_PARENT;
dentry = lookup_hash(&nd->last, nd->dentry);
if (IS_ERR(dentry))
goto fail;
if (!is_dir && nd->last.name[nd->last.len] && !dentry->d_inode)
goto enoent;
return dentry;
enoent:
dput(dentry);
dentry = ERR_PTR(-ENOENT);
fail:
return dentry;
}
int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
{
int error = may_create(dir, dentry, NULL);
if (error)
return error;
if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
return -EPERM;
if (!dir->i_op || !dir->i_op->mknod)
return -EPERM;
error = security_inode_mknod(dir, dentry, mode, dev);
if (error)
return error;
DQUOT_INIT(dir);
error = dir->i_op->mknod(dir, dentry, mode, dev);
if (!error) {
inode_dir_notify(dir, DN_CREATE);
security_inode_post_mknod(dir, dentry, mode, dev);
}
return error;
}
asmlinkage long sys_mknod(const char __user * filename, int mode, unsigned dev)
{
int error = 0;
char * tmp;
struct dentry * dentry;
struct nameidata nd;
if (S_ISDIR(mode))
return -EPERM;
tmp = getname(filename);
if (IS_ERR(tmp))
return PTR_ERR(tmp);
error = path_lookup(tmp, LOOKUP_PARENT, &nd);
if (error)
goto out;
dentry = lookup_create(&nd, 0);
error = PTR_ERR(dentry);
if (!IS_POSIXACL(nd.dentry->d_inode))
mode &= ~current->fs->umask;
if (!IS_ERR(dentry)) {
switch (mode & S_IFMT) {
case 0: case S_IFREG:
error = vfs_create(nd.dentry->d_inode,dentry,mode,&nd);
break;
case S_IFCHR: case S_IFBLK:
error = vfs_mknod(nd.dentry->d_inode,dentry,mode,
new_decode_dev(dev));
break;
case S_IFIFO: case S_IFSOCK:
error = vfs_mknod(nd.dentry->d_inode,dentry,mode,0);
break;
case S_IFDIR:
error = -EPERM;
break;
default:
error = -EINVAL;
}
dput(dentry);
}
up(&nd.dentry->d_inode->i_sem);
path_release(&nd);
out:
putname(tmp);
return error;
}
int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
int error = may_create(dir, dentry, NULL);
if (error)
return error;
if (!dir->i_op || !dir->i_op->mkdir)
return -EPERM;
mode &= (S_IRWXUGO|S_ISVTX);
error = security_inode_mkdir(dir, dentry, mode);
if (error)
return error;
DQUOT_INIT(dir);
error = dir->i_op->mkdir(dir, dentry, mode);
if (!error) {
inode_dir_notify(dir, DN_CREATE);
security_inode_post_mkdir(dir,dentry, mode);
}
return error;
}
asmlinkage long sys_mkdir(const char __user * pathname, int mode)
{
int error = 0;
char * tmp;
tmp = getname(pathname);
error = PTR_ERR(tmp);
if (!IS_ERR(tmp)) {
struct dentry *dentry;
struct nameidata nd;
error = path_lookup(tmp, LOOKUP_PARENT, &nd);
if (error)
goto out;
dentry = lookup_create(&nd, 1);
error = PTR_ERR(dentry);
if (!IS_ERR(dentry)) {
if (!IS_POSIXACL(nd.dentry->d_inode))
mode &= ~current->fs->umask;
error = vfs_mkdir(nd.dentry->d_inode, dentry, mode);
dput(dentry);
}
up(&nd.dentry->d_inode->i_sem);
path_release(&nd);
out:
putname(tmp);
}
return error;
}
/*
* We try to drop the dentry early: we should have
* a usage count of 2 if we're the only user of this
* dentry, and if that is true (possibly after pruning
* the dcache), then we drop the dentry now.
*
* A low-level filesystem can, if it choses, legally
* do a
*
* if (!d_unhashed(dentry))
* return -EBUSY;
*
* if it cannot handle the case of removing a directory
* that is still in use by something else..
*/
void dentry_unhash(struct dentry *dentry)
{
dget(dentry);
if (atomic_read(&dentry->d_count))
shrink_dcache_parent(dentry);
spin_lock(&dcache_lock);
spin_lock(&dentry->d_lock);
if (atomic_read(&dentry->d_count) == 2)
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
}
int vfs_rmdir(struct inode *dir, struct dentry *dentry)
{
int error = may_delete(dir, dentry, 1);
if (error)
return error;
if (!dir->i_op || !dir->i_op->rmdir)
return -EPERM;
DQUOT_INIT(dir);
down(&dentry->d_inode->i_sem);
dentry_unhash(dentry);
if (d_mountpoint(dentry))
error = -EBUSY;
else {
error = security_inode_rmdir(dir, dentry);
if (!error) {
error = dir->i_op->rmdir(dir, dentry);
if (!error)
dentry->d_inode->i_flags |= S_DEAD;
}
}
up(&dentry->d_inode->i_sem);
if (!error) {
inode_dir_notify(dir, DN_DELETE);
d_delete(dentry);
}
dput(dentry);
return error;
}
asmlinkage long sys_rmdir(const char __user * pathname)
{
int error = 0;
char * name;
struct dentry *dentry;
struct nameidata nd;
name = getname(pathname);
if(IS_ERR(name))
return PTR_ERR(name);
error = path_lookup(name, LOOKUP_PARENT, &nd);
if (error)
goto exit;
switch(nd.last_type) {
case LAST_DOTDOT:
error = -ENOTEMPTY;
goto exit1;
case LAST_DOT:
error = -EINVAL;
goto exit1;
case LAST_ROOT:
error = -EBUSY;
goto exit1;
}
down(&nd.dentry->d_inode->i_sem);
dentry = lookup_hash(&nd.last, nd.dentry);
error = PTR_ERR(dentry);
if (!IS_ERR(dentry)) {
error = vfs_rmdir(nd.dentry->d_inode, dentry);
dput(dentry);
}
up(&nd.dentry->d_inode->i_sem);
exit1:
path_release(&nd);
exit:
putname(name);
return error;
}
int vfs_unlink(struct inode *dir, struct dentry *dentry)
{
int error = may_delete(dir, dentry, 0);
if (error)
return error;
if (!dir->i_op || !dir->i_op->unlink)
return -EPERM;
DQUOT_INIT(dir);
down(&dentry->d_inode->i_sem);
if (d_mountpoint(dentry))
error = -EBUSY;
else {
error = security_inode_unlink(dir, dentry);
if (!error)
error = dir->i_op->unlink(dir, dentry);
}
up(&dentry->d_inode->i_sem);
/* We don't d_delete() NFS sillyrenamed files--they still exist. */
if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
d_delete(dentry);
inode_dir_notify(dir, DN_DELETE);
}
return error;
}
/*
* Make sure that the actual truncation of the file will occur outside its
* directory's i_sem. Truncate can take a long time if there is a lot of
* writeout happening, and we don't want to prevent access to the directory
* while waiting on the I/O.
*/
asmlinkage long sys_unlink(const char __user * pathname)
{
int error = 0;
char * name;
struct dentry *dentry;
struct nameidata nd;
struct inode *inode = NULL;
name = getname(pathname);
if(IS_ERR(name))
return PTR_ERR(name);
error = path_lookup(name, LOOKUP_PARENT, &nd);
if (error)
goto exit;
error = -EISDIR;
if (nd.last_type != LAST_NORM)
goto exit1;
down(&nd.dentry->d_inode->i_sem);
dentry = lookup_hash(&nd.last, nd.dentry);
error = PTR_ERR(dentry);
if (!IS_ERR(dentry)) {
/* Why not before? Because we want correct error value */
if (nd.last.name[nd.last.len])
goto slashes;
inode = dentry->d_inode;
if (inode)
atomic_inc(&inode->i_count);
error = vfs_unlink(nd.dentry->d_inode, dentry);
exit2:
dput(dentry);
}
up(&nd.dentry->d_inode->i_sem);
if (inode)
iput(inode); /* truncate the inode here */
exit1:
path_release(&nd);
exit:
putname(name);
return error;
slashes:
error = !dentry->d_inode ? -ENOENT :
S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
goto exit2;
}
int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname, int mode)
{
int error = may_create(dir, dentry, NULL);
if (error)
return error;
if (!dir->i_op || !dir->i_op->symlink)
return -EPERM;
error = security_inode_symlink(dir, dentry, oldname);
if (error)
return error;
DQUOT_INIT(dir);
error = dir->i_op->symlink(dir, dentry, oldname);
if (!error) {
inode_dir_notify(dir, DN_CREATE);
security_inode_post_symlink(dir, dentry, oldname);
}
return error;
}
asmlinkage long sys_symlink(const char __user * oldname, const char __user * newname)
{
int error = 0;
char * from;
char * to;
from = getname(oldname);
if(IS_ERR(from))
return PTR_ERR(from);
to = getname(newname);
error = PTR_ERR(to);
if (!IS_ERR(to)) {
struct dentry *dentry;
struct nameidata nd;
error = path_lookup(to, LOOKUP_PARENT, &nd);
if (error)
goto out;
dentry = lookup_create(&nd, 0);
error = PTR_ERR(dentry);
if (!IS_ERR(dentry)) {
error = vfs_symlink(nd.dentry->d_inode, dentry, from, S_IALLUGO);
dput(dentry);
}
up(&nd.dentry->d_inode->i_sem);
path_release(&nd);
out:
putname(to);
}
putname(from);
return error;
}
int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
{
struct inode *inode = old_dentry->d_inode;
int error;
if (!inode)
return -ENOENT;
error = may_create(dir, new_dentry, NULL);
if (error)
return error;
if (dir->i_sb != inode->i_sb)
return -EXDEV;
/*
* A link to an append-only or immutable file cannot be created.
*/
if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
return -EPERM;
if (!dir->i_op || !dir->i_op->link)
return -EPERM;
if (S_ISDIR(old_dentry->d_inode->i_mode))
return -EPERM;
error = security_inode_link(old_dentry, dir, new_dentry);
if (error)
return error;
down(&old_dentry->d_inode->i_sem);
DQUOT_INIT(dir);
error = dir->i_op->link(old_dentry, dir, new_dentry);
up(&old_dentry->d_inode->i_sem);
if (!error) {
inode_dir_notify(dir, DN_CREATE);
security_inode_post_link(old_dentry, dir, new_dentry);
}
return error;
}
/*
* Hardlinks are often used in delicate situations. We avoid
* security-related surprises by not following symlinks on the
* newname. --KAB
*
* We don't follow them on the oldname either to be compatible
* with linux 2.0, and to avoid hard-linking to directories
* and other special files. --ADM
*/
asmlinkage long sys_link(const char __user * oldname, const char __user * newname)
{
struct dentry *new_dentry;
struct nameidata nd, old_nd;
int error;
char * to;
to = getname(newname);
if (IS_ERR(to))
return PTR_ERR(to);
error = __user_walk(oldname, 0, &old_nd);
if (error)
goto exit;
error = path_lookup(to, LOOKUP_PARENT, &nd);
if (error)
goto out;
error = -EXDEV;
if (old_nd.mnt != nd.mnt)
goto out_release;
new_dentry = lookup_create(&nd, 0);
error = PTR_ERR(new_dentry);
if (!IS_ERR(new_dentry)) {
error = vfs_link(old_nd.dentry, nd.dentry->d_inode, new_dentry);
dput(new_dentry);
}
up(&nd.dentry->d_inode->i_sem);
out_release:
path_release(&nd);
out:
path_release(&old_nd);
exit:
putname(to);
return error;
}
/*
* The worst of all namespace operations - renaming directory. "Perverted"
* doesn't even start to describe it. Somebody in UCB had a heck of a trip...
* Problems:
* a) we can get into loop creation. Check is done in is_subdir().
* b) race potential - two innocent renames can create a loop together.
* That's where 4.4 screws up. Current fix: serialization on
* sb->s_vfs_rename_sem. We might be more accurate, but that's another
* story.
* c) we have to lock _three_ objects - parents and victim (if it exists).
* And that - after we got ->i_sem on parents (until then we don't know
* whether the target exists). Solution: try to be smart with locking
* order for inodes. We rely on the fact that tree topology may change
* only under ->s_vfs_rename_sem _and_ that parent of the object we
* move will be locked. Thus we can rank directories by the tree
* (ancestors first) and rank all non-directories after them.
* That works since everybody except rename does "lock parent, lookup,
* lock child" and rename is under ->s_vfs_rename_sem.
* HOWEVER, it relies on the assumption that any object with ->lookup()
* has no more than 1 dentry. If "hybrid" objects will ever appear,
* we'd better make sure that there's no link(2) for them.
* d) some filesystems don't support opened-but-unlinked directories,
* either because of layout or because they are not ready to deal with
* all cases correctly. The latter will be fixed (taking this sort of
* stuff into VFS), but the former is not going away. Solution: the same
* trick as in rmdir().
* e) conversion from fhandle to dentry may come in the wrong moment - when
* we are removing the target. Solution: we will have to grab ->i_sem
* in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
* ->i_sem on parents, which works but leads to some truely excessive
* locking].
*/
int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry)
{
int error = 0;
struct inode *target;
/*
* If we are going to change the parent - check write permissions,
* we'll need to flip '..'.
*/
if (new_dir != old_dir) {
error = permission(old_dentry->d_inode, MAY_WRITE, NULL);
if (error)
return error;
}
error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
if (error)
return error;
target = new_dentry->d_inode;
if (target) {
down(&target->i_sem);
dentry_unhash(new_dentry);
}
if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
error = -EBUSY;
else
error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
if (target) {
if (!error)
target->i_flags |= S_DEAD;
up(&target->i_sem);
if (d_unhashed(new_dentry))
d_rehash(new_dentry);
dput(new_dentry);
}
if (!error) {
d_move(old_dentry,new_dentry);
security_inode_post_rename(old_dir, old_dentry,
new_dir, new_dentry);
}
return error;
}
int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry)
{
struct inode *target;
int error;
error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
if (error)
return error;
dget(new_dentry);
target = new_dentry->d_inode;
if (target)
down(&target->i_sem);
if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
error = -EBUSY;
else
error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
if (!error) {
/* The following d_move() should become unconditional */
if (!(old_dir->i_sb->s_type->fs_flags & FS_ODD_RENAME))
d_move(old_dentry, new_dentry);
security_inode_post_rename(old_dir, old_dentry, new_dir, new_dentry);
}
if (target)
up(&target->i_sem);
dput(new_dentry);
return error;
}
int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry)
{
int error;
int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
if (old_dentry->d_inode == new_dentry->d_inode)
return 0;
error = may_delete(old_dir, old_dentry, is_dir);
if (error)
return error;
if (!new_dentry->d_inode)
error = may_create(new_dir, new_dentry, NULL);
else
error = may_delete(new_dir, new_dentry, is_dir);
if (error)
return error;
if (!old_dir->i_op || !old_dir->i_op->rename)
return -EPERM;
DQUOT_INIT(old_dir);
DQUOT_INIT(new_dir);
if (is_dir)
error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
else
error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
if (!error) {
if (old_dir == new_dir)
inode_dir_notify(old_dir, DN_RENAME);
else {
inode_dir_notify(old_dir, DN_DELETE);
inode_dir_notify(new_dir, DN_CREATE);
}
}
return error;
}
static inline int do_rename(const char * oldname, const char * newname)
{
int error = 0;
struct dentry * old_dir, * new_dir;
struct dentry * old_dentry, *new_dentry;
struct dentry * trap;
struct nameidata oldnd, newnd;
error = path_lookup(oldname, LOOKUP_PARENT, &oldnd);
if (error)
goto exit;
error = path_lookup(newname, LOOKUP_PARENT, &newnd);
if (error)
goto exit1;
error = -EXDEV;
if (oldnd.mnt != newnd.mnt)
goto exit2;
old_dir = oldnd.dentry;
error = -EBUSY;
if (oldnd.last_type != LAST_NORM)
goto exit2;
new_dir = newnd.dentry;
if (newnd.last_type != LAST_NORM)
goto exit2;
trap = lock_rename(new_dir, old_dir);
old_dentry = lookup_hash(&oldnd.last, old_dir);
error = PTR_ERR(old_dentry);
if (IS_ERR(old_dentry))
goto exit3;
/* source must exist */
error = -ENOENT;
if (!old_dentry->d_inode)
goto exit4;
/* unless the source is a directory trailing slashes give -ENOTDIR */
if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
error = -ENOTDIR;
if (oldnd.last.name[oldnd.last.len])
goto exit4;
if (newnd.last.name[newnd.last.len])
goto exit4;
}
/* source should not be ancestor of target */
error = -EINVAL;
if (old_dentry == trap)
goto exit4;
new_dentry = lookup_hash(&newnd.last, new_dir);
error = PTR_ERR(new_dentry);
if (IS_ERR(new_dentry))
goto exit4;
/* target should not be an ancestor of source */
error = -ENOTEMPTY;
if (new_dentry == trap)
goto exit5;
error = vfs_rename(old_dir->d_inode, old_dentry,
new_dir->d_inode, new_dentry);
exit5:
dput(new_dentry);
exit4:
dput(old_dentry);
exit3:
unlock_rename(new_dir, old_dir);
exit2:
path_release(&newnd);
exit1:
path_release(&oldnd);
exit:
return error;
}
asmlinkage long sys_rename(const char __user * oldname, const char __user * newname)
{
int error;
char * from;
char * to;
from = getname(oldname);
if(IS_ERR(from))
return PTR_ERR(from);
to = getname(newname);
error = PTR_ERR(to);
if (!IS_ERR(to)) {
error = do_rename(from,to);
putname(to);
}
putname(from);
return error;
}
int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
{
int len;
len = PTR_ERR(link);
if (IS_ERR(link))
goto out;
len = strlen(link);
if (len > (unsigned) buflen)
len = buflen;
if (copy_to_user(buffer, link, len))
len = -EFAULT;
out:
return len;
}
/*
* A helper for ->readlink(). This should be used *ONLY* for symlinks that
* have ->follow_link() touching nd only in nd_set_link(). Using (or not
* using) it for any given inode is up to filesystem.
*/
int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
{
struct nameidata nd;
int res;
nd.depth = 0;
res = dentry->d_inode->i_op->follow_link(dentry, &nd);
if (!res) {
res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
if (dentry->d_inode->i_op->put_link)
dentry->d_inode->i_op->put_link(dentry, &nd);
}
return res;
}
int vfs_follow_link(struct nameidata *nd, const char *link)
{
return __vfs_follow_link(nd, link);
}
/* get the link contents into pagecache */
static char *page_getlink(struct dentry * dentry, struct page **ppage)
{
struct page * page;
struct address_space *mapping = dentry->d_inode->i_mapping;
page = read_cache_page(mapping, 0, (filler_t *)mapping->a_ops->readpage,
NULL);
if (IS_ERR(page))
goto sync_fail;
wait_on_page_locked(page);
if (!PageUptodate(page))
goto async_fail;
*ppage = page;
return kmap(page);
async_fail:
page_cache_release(page);
return ERR_PTR(-EIO);
sync_fail:
return (char*)page;
}
int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
{
struct page *page = NULL;
char *s = page_getlink(dentry, &page);
int res = vfs_readlink(dentry,buffer,buflen,s);
if (page) {
kunmap(page);
page_cache_release(page);
}
return res;
}
int page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
{
struct page *page;
nd_set_link(nd, page_getlink(dentry, &page));
return 0;
}
void page_put_link(struct dentry *dentry, struct nameidata *nd)
{
if (!IS_ERR(nd_get_link(nd))) {
struct page *page;
page = find_get_page(dentry->d_inode->i_mapping, 0);
if (!page)
BUG();
kunmap(page);
page_cache_release(page);
page_cache_release(page);
}
}
int page_symlink(struct inode *inode, const char *symname, int len)
{
struct address_space *mapping = inode->i_mapping;
struct page *page = grab_cache_page(mapping, 0);
int err = -ENOMEM;
char *kaddr;
if (!page)
goto fail;
err = mapping->a_ops->prepare_write(NULL, page, 0, len-1);
if (err)
goto fail_map;
kaddr = kmap_atomic(page, KM_USER0);
memcpy(kaddr, symname, len-1);
kunmap_atomic(kaddr, KM_USER0);
mapping->a_ops->commit_write(NULL, page, 0, len-1);
/*
* Notice that we are _not_ going to block here - end of page is
* unmapped, so this will only try to map the rest of page, see
* that it is unmapped (typically even will not look into inode -
* ->i_size will be enough for everything) and zero it out.
* OTOH it's obviously correct and should make the page up-to-date.
*/
if (!PageUptodate(page)) {
err = mapping->a_ops->readpage(NULL, page);
wait_on_page_locked(page);
} else {
unlock_page(page);
}
page_cache_release(page);
if (err < 0)
goto fail;
mark_inode_dirty(inode);
return 0;
fail_map:
unlock_page(page);
page_cache_release(page);
fail:
return err;
}
struct inode_operations page_symlink_inode_operations = {
.readlink = generic_readlink,
.follow_link = page_follow_link_light,
.put_link = page_put_link,
};
EXPORT_SYMBOL(__user_walk);
EXPORT_SYMBOL(follow_down);
EXPORT_SYMBOL(follow_up);
EXPORT_SYMBOL(get_write_access); /* binfmt_aout */
EXPORT_SYMBOL(getname);
EXPORT_SYMBOL(lock_rename);
EXPORT_SYMBOL(lookup_hash);
EXPORT_SYMBOL(lookup_one_len);
EXPORT_SYMBOL(page_follow_link_light);
EXPORT_SYMBOL(page_put_link);
EXPORT_SYMBOL(page_readlink);
EXPORT_SYMBOL(page_symlink);
EXPORT_SYMBOL(page_symlink_inode_operations);
EXPORT_SYMBOL(path_lookup);
EXPORT_SYMBOL(path_release);
EXPORT_SYMBOL(path_walk);
EXPORT_SYMBOL(permission);
EXPORT_SYMBOL(unlock_rename);
EXPORT_SYMBOL(vfs_create);
EXPORT_SYMBOL(vfs_follow_link);
EXPORT_SYMBOL(vfs_link);
EXPORT_SYMBOL(vfs_mkdir);
EXPORT_SYMBOL(vfs_mknod);
EXPORT_SYMBOL(generic_permission);
EXPORT_SYMBOL(vfs_readlink);
EXPORT_SYMBOL(vfs_rename);
EXPORT_SYMBOL(vfs_rmdir);
EXPORT_SYMBOL(vfs_symlink);
EXPORT_SYMBOL(vfs_unlink);
EXPORT_SYMBOL(dentry_unhash);
EXPORT_SYMBOL(generic_readlink);
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