security: introduce kernel_module_from_file hook
Now that kernel module origins can be reasoned about, provide a hook to the LSMs to make policy decisions about the module file. This will let Chrome OS enforce that loadable kernel modules can only come from its read-only hash-verified root filesystem. Other LSMs can, for example, read extended attributes for signatures, etc. Signed-off-by: Kees Cook <keescook@chromium.org> Acked-by: Serge E. Hallyn <serge.hallyn@canonical.com> Acked-by: Eric Paris <eparis@redhat.com> Acked-by: Mimi Zohar <zohar@us.ibm.com> Acked-by: James Morris <james.l.morris@oracle.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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@ -694,6 +694,12 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
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* userspace to load a kernel module with the given name.
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* @kmod_name name of the module requested by the kernel
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* Return 0 if successful.
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* @kernel_module_from_file:
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* Load a kernel module from userspace.
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* @file contains the file structure pointing to the file containing
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* the kernel module to load. If the module is being loaded from a blob,
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* this argument will be NULL.
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* Return 0 if permission is granted.
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* @task_fix_setuid:
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* Update the module's state after setting one or more of the user
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* identity attributes of the current process. The @flags parameter
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@ -1508,6 +1514,7 @@ struct security_operations {
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int (*kernel_act_as)(struct cred *new, u32 secid);
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int (*kernel_create_files_as)(struct cred *new, struct inode *inode);
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int (*kernel_module_request)(char *kmod_name);
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int (*kernel_module_from_file)(struct file *file);
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int (*task_fix_setuid) (struct cred *new, const struct cred *old,
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int flags);
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int (*task_setpgid) (struct task_struct *p, pid_t pgid);
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@ -1765,6 +1772,7 @@ void security_transfer_creds(struct cred *new, const struct cred *old);
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int security_kernel_act_as(struct cred *new, u32 secid);
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int security_kernel_create_files_as(struct cred *new, struct inode *inode);
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int security_kernel_module_request(char *kmod_name);
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int security_kernel_module_from_file(struct file *file);
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int security_task_fix_setuid(struct cred *new, const struct cred *old,
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int flags);
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int security_task_setpgid(struct task_struct *p, pid_t pgid);
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@ -2278,6 +2286,11 @@ static inline int security_kernel_module_request(char *kmod_name)
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return 0;
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}
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static inline int security_kernel_module_from_file(struct file *file)
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{
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return 0;
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}
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static inline int security_task_fix_setuid(struct cred *new,
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const struct cred *old,
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int flags)
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@ -29,6 +29,7 @@
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#include <linux/vmalloc.h>
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#include <linux/elf.h>
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#include <linux/proc_fs.h>
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#include <linux/security.h>
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#include <linux/seq_file.h>
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#include <linux/syscalls.h>
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#include <linux/fcntl.h>
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@ -2485,10 +2486,16 @@ static int elf_header_check(struct load_info *info)
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static int copy_module_from_user(const void __user *umod, unsigned long len,
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struct load_info *info)
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{
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int err;
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info->len = len;
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if (info->len < sizeof(*(info->hdr)))
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return -ENOEXEC;
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err = security_kernel_module_from_file(NULL);
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if (err)
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return err;
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/* Suck in entire file: we'll want most of it. */
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info->hdr = vmalloc(info->len);
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if (!info->hdr)
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@ -2515,6 +2522,10 @@ static int copy_module_from_fd(int fd, struct load_info *info)
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if (!file)
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return -ENOEXEC;
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err = security_kernel_module_from_file(file);
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if (err)
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goto out;
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err = vfs_getattr(file->f_vfsmnt, file->f_dentry, &stat);
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if (err)
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goto out;
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@ -395,6 +395,11 @@ static int cap_kernel_module_request(char *kmod_name)
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return 0;
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}
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static int cap_kernel_module_from_file(struct file *file)
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{
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return 0;
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}
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static int cap_task_setpgid(struct task_struct *p, pid_t pgid)
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{
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return 0;
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@ -967,6 +972,7 @@ void __init security_fixup_ops(struct security_operations *ops)
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set_to_cap_if_null(ops, kernel_act_as);
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set_to_cap_if_null(ops, kernel_create_files_as);
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set_to_cap_if_null(ops, kernel_module_request);
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set_to_cap_if_null(ops, kernel_module_from_file);
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set_to_cap_if_null(ops, task_fix_setuid);
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set_to_cap_if_null(ops, task_setpgid);
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set_to_cap_if_null(ops, task_getpgid);
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@ -820,6 +820,11 @@ int security_kernel_module_request(char *kmod_name)
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return security_ops->kernel_module_request(kmod_name);
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}
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int security_kernel_module_from_file(struct file *file)
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{
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return security_ops->kernel_module_from_file(file);
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}
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int security_task_fix_setuid(struct cred *new, const struct cred *old,
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int flags)
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{
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