Pull ipc namespace update from Al Viro:
"Rik's patches reducing the amount of synchronize_rcu() triggered by
ipc namespace destruction.
I've some pending stuff reducing that on the normal umount side, but
it's nowhere near ready and Rik's stuff shouldn't be held back due to
conflicts - I'll just redo the parts of my series that stray into
ipc/*"
* 'work.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
ipc,namespace: batch free ipc_namespace structures
ipc,namespace: make ipc namespace allocation wait for pending free
Instead of waiting for an RCU grace period between each ipc_namespace
structure that is being freed, wait an RCU grace period for every batch
of ipc_namespace structures.
Thanks to Al Viro for the suggestion of the helper function.
This speeds up the run time of the test case that allocates ipc_namespaces
in a loop from 6 minutes, to a little over 1 second:
real 0m1.192s
user 0m0.038s
sys 0m1.152s
Signed-off-by: Rik van Riel <riel@surriel.com>
Reported-by: Chris Mason <clm@meta.com>
Tested-by: Giuseppe Scrivano <gscrivan@redhat.com>
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Convert to struct mnt_idmap.
Last cycle we merged the necessary infrastructure in
256c8aed2b ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.
Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.
Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.
Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Convert to struct mnt_idmap.
Last cycle we merged the necessary infrastructure in
256c8aed2b ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.
Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.
Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.
Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Convert to struct mnt_idmap.
Last cycle we merged the necessary infrastructure in
256c8aed2b ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.
Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.
Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.
Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
When setup_mq_sysctls() failed in init_mqueue_fs(), mqueue_inode_cachep is
not released. In order to fix this issue, the release path is reordered.
Link: https://lkml.kernel.org/r/20221209092929.1978875-1-shaozhengchao@huawei.com
Fixes: dc55e35f9e ("ipc: Store mqueue sysctls in the ipc namespace")
Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
Cc: Alexey Gladkov <legion@kernel.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Jingyu Wang <jingyuwang_vip@163.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Waiman Long <longman@redhat.com>
Cc: Wei Yongjun <weiyongjun1@huawei.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Cc: Yu Zhe <yuzhe@nfschina.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
- Valentin Schneider makes crash-kexec work properly when invoked from
an NMI-time panic.
- ntfs bugfixes from Hawkins Jiawei
- Jiebin Sun improves IPC msg scalability by replacing atomic_t's with
percpu counters.
- nilfs2 cleanups from Minghao Chi
- lots of other single patches all over the tree!
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Merge tag 'mm-nonmm-stable-2022-10-11' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull non-MM updates from Andrew Morton:
- hfs and hfsplus kmap API modernization (Fabio Francesco)
- make crash-kexec work properly when invoked from an NMI-time panic
(Valentin Schneider)
- ntfs bugfixes (Hawkins Jiawei)
- improve IPC msg scalability by replacing atomic_t's with percpu
counters (Jiebin Sun)
- nilfs2 cleanups (Minghao Chi)
- lots of other single patches all over the tree!
* tag 'mm-nonmm-stable-2022-10-11' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (71 commits)
include/linux/entry-common.h: remove has_signal comment of arch_do_signal_or_restart() prototype
proc: test how it holds up with mapping'less process
mailmap: update Frank Rowand email address
ia64: mca: use strscpy() is more robust and safer
init/Kconfig: fix unmet direct dependencies
ia64: update config files
nilfs2: replace WARN_ONs by nilfs_error for checkpoint acquisition failure
fork: remove duplicate included header files
init/main.c: remove unnecessary (void*) conversions
proc: mark more files as permanent
nilfs2: remove the unneeded result variable
nilfs2: delete unnecessary checks before brelse()
checkpatch: warn for non-standard fixes tag style
usr/gen_init_cpio.c: remove unnecessary -1 values from int file
ipc/msg: mitigate the lock contention with percpu counter
percpu: add percpu_counter_add_local and percpu_counter_sub_local
fs/ocfs2: fix repeated words in comments
relay: use kvcalloc to alloc page array in relay_alloc_page_array
proc: make config PROC_CHILDREN depend on PROC_FS
fs: uninline inode_maybe_inc_iversion()
...
A fix for a unlikely but possible memory leak.
Hangyu Hua (1):
ipc: mqueue: fix possible memory leak in init_mqueue_fs()
ipc/mqueue.c | 1 +
1 file changed, 1 insertion(+)
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Merge tag 'retire_mq_sysctls-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull mqueue fix from Eric Biederman:
"A fix for an unlikely but possible memory leak"
* tag 'retire_mq_sysctls-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
ipc: mqueue: fix possible memory leak in init_mqueue_fs()
iput() already handles null and non-null parameters, so there is no need
to use if().
Link: https://lkml.kernel.org/r/20220908185452.76590-1-jingyuwang_vip@163.com
Signed-off-by: Jingyu Wang <jingyuwang_vip@163.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
commit db7cfc3809 ("ipc: Free mq_sysctls if ipc namespace creation
failed")
Here's a similar memory leak to the one fixed by the patch above.
retire_mq_sysctls need to be called when init_mqueue_fs fails after
setup_mq_sysctls.
Fixes: dc55e35f9e ("ipc: Store mqueue sysctls in the ipc namespace")
Signed-off-by: Hangyu Hua <hbh25y@gmail.com>
Link: https://lkml.kernel.org/r/20220715062301.19311-1-hbh25y@gmail.com
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
per ipc namespace. Previously these sysctls depended upon a hack to
simulate being per ipc namespace by looking up the ipc namespace in
read or write. With this set of changes the ipc sysctls are
registered per ipc namespace and open looks up the ipc namespace.
Not only does this series of changes ensure the traditional binding at
open time happens, but it sets a foundation for being able to relax the
permission checks to allow a user namspace root to change the ipc sysctls
for an ipc namespace that the user namespace root requires. To do this
requires the ipc namespace to be known at open time.
These changes were sent for v5.18[1] but were dropped because some
additional cleanups were requested. Linus has given his nod[2] to the
cleanups so I hope enough cleanups are present this time.
[1] https://lkml.kernel.org/r/877d8kfmdp.fsf@email.froward.int.ebiederm.org
[2] https://lkml.kernel.org/r/CAHk-=whi2SzU4XT_FsdTCAuK2qtYmH+-hwi1cbSdG8zu0KXL=g@mail.gmail.com
Alexey Gladkov (6):
ipc: Store mqueue sysctls in the ipc namespace
ipc: Store ipc sysctls in the ipc namespace
ipc: Use the same namespace to modify and validate
ipc: Remove extra1 field abuse to pass ipc namespace
ipc: Check permissions for checkpoint_restart sysctls at open time
ipc: Remove extra braces
include/linux/ipc_namespace.h | 37 +++++++-
ipc/ipc_sysctl.c | 205 +++++++++++++++++++++++++-----------------
ipc/mq_sysctl.c | 121 +++++++++++++------------
ipc/mqueue.c | 10 +--
ipc/namespace.c | 10 +++
5 files changed, 238 insertions(+), 145 deletions(-)
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Merge tag 'per-namespace-ipc-sysctls-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull ipc sysctl namespace updates from Eric Biederman:
"This updates the ipc sysctls so that they are fundamentally per ipc
namespace. Previously these sysctls depended upon a hack to simulate
being per ipc namespace by looking up the ipc namespace in read or
write. With this set of changes the ipc sysctls are registered per ipc
namespace and open looks up the ipc namespace.
Not only does this series of changes ensure the traditional binding at
open time happens, but it sets a foundation for being able to relax
the permission checks to allow a user namspace root to change the ipc
sysctls for an ipc namespace that the user namespace root requires. To
do this requires the ipc namespace to be known at open time"
* tag 'per-namespace-ipc-sysctls-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
ipc: Remove extra braces
ipc: Check permissions for checkpoint_restart sysctls at open time
ipc: Remove extra1 field abuse to pass ipc namespace
ipc: Use the same namespace to modify and validate
ipc: Store ipc sysctls in the ipc namespace
ipc: Store mqueue sysctls in the ipc namespace
When running the stress-ng clone benchmark with multiple testing threads,
it was found that there were significant spinlock contention in sget_fc().
The contended spinlock was the sb_lock. It is under heavy contention
because the following code in the critcal section of sget_fc():
hlist_for_each_entry(old, &fc->fs_type->fs_supers, s_instances) {
if (test(old, fc))
goto share_extant_sb;
}
After testing with added instrumentation code, it was found that the
benchmark could generate thousands of ipc namespaces with the
corresponding number of entries in the mqueue's fs_supers list where the
namespaces are the key for the search. This leads to excessive time in
scanning the list for a match.
Looking back at the mqueue calling sequence leading to sget_fc():
mq_init_ns()
=> mq_create_mount()
=> fc_mount()
=> vfs_get_tree()
=> mqueue_get_tree()
=> get_tree_keyed()
=> vfs_get_super()
=> sget_fc()
Currently, mq_init_ns() is the only mqueue function that will indirectly
call mqueue_get_tree() with a newly allocated ipc namespace as the key for
searching. As a result, there will never be a match with the exising ipc
namespaces stored in the mqueue's fs_supers list.
So using get_tree_keyed() to do an existing ipc namespace search is just a
waste of time. Instead, we could use get_tree_nodev() to eliminate the
useless search. By doing so, we can greatly reduce the sb_lock hold time
and avoid the spinlock contention problem in case a large number of ipc
namespaces are present.
Of course, if the code is modified in the future to allow
mqueue_get_tree() to be called with an existing ipc namespace instead of a
new one, we will have to use get_tree_keyed() in this case.
The following stress-ng clone benchmark command was run on a 2-socket
48-core Intel system:
./stress-ng --clone 32 --verbose --oomable --metrics-brief -t 20
The "bogo ops/s" increased from 5948.45 before patch to 9137.06 after
patch. This is an increase of 54% in performance.
Link: https://lkml.kernel.org/r/20220121172315.19652-1-longman@redhat.com
Fixes: 935c6912b1 ("ipc: Convert mqueue fs to fs_context")
Signed-off-by: Waiman Long <longman@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: David Howells <dhowells@redhat.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The inode allocation is supposed to use alloc_inode_sb(), so convert
kmem_cache_alloc() of all filesystems to alloc_inode_sb().
Link: https://lkml.kernel.org/r/20220228122126.37293-5-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Theodore Ts'o <tytso@mit.edu> [ext4]
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Alex Shi <alexs@kernel.org>
Cc: Anna Schumaker <Anna.Schumaker@Netapp.com>
Cc: Chao Yu <chao@kernel.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Fam Zheng <fam.zheng@bytedance.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kari Argillander <kari.argillander@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Right now, the mqueue sysctls take ipc namespaces into account in a
rather hacky way. This works in most cases, but does not respect the
user namespace.
Within the user namespace, the user cannot change the /proc/sys/fs/mqueue/*
parametres. This poses a problem in the rootless containers.
To solve this I changed the implementation of the mqueue sysctls just
like some other sysctls.
So far, the changes do not provide additional access to files. This will
be done in a future patch.
v3:
* Don't implemenet set_permissions to keep the current behavior.
v2:
* Fixed compilation problem if CONFIG_POSIX_MQUEUE_SYSCTL is not
specified.
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Alexey Gladkov <legion@kernel.org>
Link: https://lkml.kernel.org/r/b0ccbb2489119f1f20c737cf1930c3a9c4e4243a.1644862280.git.legion@kernel.org
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Pull user namespace rlimit handling update from Eric Biederman:
"This is the work mainly by Alexey Gladkov to limit rlimits to the
rlimits of the user that created a user namespace, and to allow users
to have stricter limits on the resources created within a user
namespace."
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
cred: add missing return error code when set_cred_ucounts() failed
ucounts: Silence warning in dec_rlimit_ucounts
ucounts: Set ucount_max to the largest positive value the type can hold
kselftests: Add test to check for rlimit changes in different user namespaces
Reimplement RLIMIT_MEMLOCK on top of ucounts
Reimplement RLIMIT_SIGPENDING on top of ucounts
Reimplement RLIMIT_MSGQUEUE on top of ucounts
Reimplement RLIMIT_NPROC on top of ucounts
Use atomic_t for ucounts reference counting
Add a reference to ucounts for each cred
Increase size of ucounts to atomic_long_t
do_mq_timedreceive calls wq_sleep with a stack local address. The
sender (do_mq_timedsend) uses this address to later call pipelined_send.
This leads to a very hard to trigger race where a do_mq_timedreceive
call might return and leave do_mq_timedsend to rely on an invalid
address, causing the following crash:
RIP: 0010:wake_q_add_safe+0x13/0x60
Call Trace:
__x64_sys_mq_timedsend+0x2a9/0x490
do_syscall_64+0x80/0x680
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f5928e40343
The race occurs as:
1. do_mq_timedreceive calls wq_sleep with the address of `struct
ext_wait_queue` on function stack (aliased as `ewq_addr` here) - it
holds a valid `struct ext_wait_queue *` as long as the stack has not
been overwritten.
2. `ewq_addr` gets added to info->e_wait_q[RECV].list in wq_add, and
do_mq_timedsend receives it via wq_get_first_waiter(info, RECV) to call
__pipelined_op.
3. Sender calls __pipelined_op::smp_store_release(&this->state,
STATE_READY). Here is where the race window begins. (`this` is
`ewq_addr`.)
4. If the receiver wakes up now in do_mq_timedreceive::wq_sleep, it
will see `state == STATE_READY` and break.
5. do_mq_timedreceive returns, and `ewq_addr` is no longer guaranteed
to be a `struct ext_wait_queue *` since it was on do_mq_timedreceive's
stack. (Although the address may not get overwritten until another
function happens to touch it, which means it can persist around for an
indefinite time.)
6. do_mq_timedsend::__pipelined_op() still believes `ewq_addr` is a
`struct ext_wait_queue *`, and uses it to find a task_struct to pass to
the wake_q_add_safe call. In the lucky case where nothing has
overwritten `ewq_addr` yet, `ewq_addr->task` is the right task_struct.
In the unlucky case, __pipelined_op::wake_q_add_safe gets handed a
bogus address as the receiver's task_struct causing the crash.
do_mq_timedsend::__pipelined_op() should not dereference `this` after
setting STATE_READY, as the receiver counterpart is now free to return.
Change __pipelined_op to call wake_q_add_safe on the receiver's
task_struct returned by get_task_struct, instead of dereferencing `this`
which sits on the receiver's stack.
As Manfred pointed out, the race potentially also exists in
ipc/msg.c::expunge_all and ipc/sem.c::wake_up_sem_queue_prepare. Fix
those in the same way.
Link: https://lkml.kernel.org/r/20210510102950.12551-1-varad.gautam@suse.com
Fixes: c5b2cbdbda ("ipc/mqueue.c: update/document memory barriers")
Fixes: 8116b54e7e ("ipc/sem.c: document and update memory barriers")
Fixes: 0d97a82ba8 ("ipc/msg.c: update and document memory barriers")
Signed-off-by: Varad Gautam <varad.gautam@suse.com>
Reported-by: Matthias von Faber <matthias.vonfaber@aox-tech.de>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The rlimit counter is tied to uid in the user_namespace. This allows
rlimit values to be specified in userns even if they are already
globally exceeded by the user. However, the value of the previous
user_namespaces cannot be exceeded.
Signed-off-by: Alexey Gladkov <legion@kernel.org>
Link: https://lkml.kernel.org/r/2531f42f7884bbfee56a978040b3e0d25cdf6cde.1619094428.git.legion@kernel.org
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Extend some inode methods with an additional user namespace argument. A
filesystem that is aware of idmapped mounts will receive the user
namespace the mount has been marked with. This can be used for
additional permission checking and also to enable filesystems to
translate between uids and gids if they need to. We have implemented all
relevant helpers in earlier patches.
As requested we simply extend the exisiting inode method instead of
introducing new ones. This is a little more code churn but it's mostly
mechanical and doesnt't leave us with additional inode methods.
Link: https://lore.kernel.org/r/20210121131959.646623-25-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
The various vfs_*() helpers are called by filesystems or by the vfs
itself to perform core operations such as create, link, mkdir, mknod, rename,
rmdir, tmpfile and unlink. Enable them to handle idmapped mounts. If the
inode is accessed through an idmapped mount map it into the
mount's user namespace and pass it down. Afterwards the checks and
operations are identical to non-idmapped mounts. If the initial user
namespace is passed nothing changes so non-idmapped mounts will see
identical behavior as before.
Link: https://lore.kernel.org/r/20210121131959.646623-15-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
The two helpers inode_permission() and generic_permission() are used by
the vfs to perform basic permission checking by verifying that the
caller is privileged over an inode. In order to handle idmapped mounts
we extend the two helpers with an additional user namespace argument.
On idmapped mounts the two helpers will make sure to map the inode
according to the mount's user namespace and then peform identical
permission checks to inode_permission() and generic_permission(). If the
initial user namespace is passed nothing changes so non-idmapped mounts
will see identical behavior as before.
Link: https://lore.kernel.org/r/20210121131959.646623-6-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Acked-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Update and document memory barriers for mqueue.c:
- ewp->state is read without any locks, thus READ_ONCE is required.
- add smp_aquire__after_ctrl_dep() after the READ_ONCE, we need
acquire semantics if the value is STATE_READY.
- use wake_q_add_safe()
- document why __set_current_state() may be used:
Reading task->state cannot happen before the wake_q_add() call,
which happens while holding info->lock. Thus the spin_unlock()
is the RELEASE, and the spin_lock() is the ACQUIRE.
For completeness: there is also a 3 CPU scenario, if the to be woken
up task is already on another wake_q.
Then:
- CPU1: spin_unlock() of the task that goes to sleep is the RELEASE
- CPU2: the spin_lock() of the waker is the ACQUIRE
- CPU2: smp_mb__before_atomic inside wake_q_add() is the RELEASE
- CPU3: smp_mb__after_spinlock() inside try_to_wake_up() is the ACQUIRE
Link: http://lkml.kernel.org/r/20191020123305.14715-4-manfred@colorfullife.com
Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Reviewed-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Waiman Long <longman@redhat.com>
Cc: <1vier1@web.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Null pointers were assigned to local variables in a few cases as exception
handling. The jump target “out” was used where no meaningful data
processing actions should eventually be performed by branches of an if
statement then. Use an additional jump target for calling dev_kfree_skb()
directly.
Return also directly after error conditions were detected when no extra
clean-up is needed by this function implementation.
Link: http://lkml.kernel.org/r/592ef10e-0b69-72d0-9789-fc48f638fdfd@web.de
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
dev_kfree_skb() input parameter validation, thus the test around the call
is not needed.
This issue was detected by using the Coccinelle software.
Link: http://lkml.kernel.org/r/07477187-63e5-cc80-34c1-32dd16b38e12@web.de
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull vfs mount updates from Al Viro:
"The first part of mount updates.
Convert filesystems to use the new mount API"
* 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (63 commits)
mnt_init(): call shmem_init() unconditionally
constify ksys_mount() string arguments
don't bother with registering rootfs
init_rootfs(): don't bother with init_ramfs_fs()
vfs: Convert smackfs to use the new mount API
vfs: Convert selinuxfs to use the new mount API
vfs: Convert securityfs to use the new mount API
vfs: Convert apparmorfs to use the new mount API
vfs: Convert openpromfs to use the new mount API
vfs: Convert xenfs to use the new mount API
vfs: Convert gadgetfs to use the new mount API
vfs: Convert oprofilefs to use the new mount API
vfs: Convert ibmasmfs to use the new mount API
vfs: Convert qib_fs/ipathfs to use the new mount API
vfs: Convert efivarfs to use the new mount API
vfs: Convert configfs to use the new mount API
vfs: Convert binfmt_misc to use the new mount API
convenience helper: get_tree_single()
convenience helper get_tree_nodev()
vfs: Kill sget_userns()
...
Andreas Christoforou reported:
UBSAN: Undefined behaviour in ipc/mqueue.c:414:49 signed integer overflow:
9 * 2305843009213693951 cannot be represented in type 'long int'
...
Call Trace:
mqueue_evict_inode+0x8e7/0xa10 ipc/mqueue.c:414
evict+0x472/0x8c0 fs/inode.c:558
iput_final fs/inode.c:1547 [inline]
iput+0x51d/0x8c0 fs/inode.c:1573
mqueue_get_inode+0x8eb/0x1070 ipc/mqueue.c:320
mqueue_create_attr+0x198/0x440 ipc/mqueue.c:459
vfs_mkobj+0x39e/0x580 fs/namei.c:2892
prepare_open ipc/mqueue.c:731 [inline]
do_mq_open+0x6da/0x8e0 ipc/mqueue.c:771
Which could be triggered by:
struct mq_attr attr = {
.mq_flags = 0,
.mq_maxmsg = 9,
.mq_msgsize = 0x1fffffffffffffff,
.mq_curmsgs = 0,
};
if (mq_open("/testing", 0x40, 3, &attr) == (mqd_t) -1)
perror("mq_open");
mqueue_get_inode() was correctly rejecting the giant mq_msgsize, and
preparing to return -EINVAL. During the cleanup, it calls
mqueue_evict_inode() which performed resource usage tracking math for
updating "user", before checking if there was a valid "user" at all
(which would indicate that the calculations would be sane). Instead,
delay this check to after seeing a valid "user".
The overflow was real, but the results went unused, so while the flaw is
harmless, it's noisy for kernel fuzzers, so just fix it by moving the
calculation under the non-NULL "user" where it actually gets used.
Link: http://lkml.kernel.org/r/201906072207.ECB65450@keescook
Signed-off-by: Kees Cook <keescook@chromium.org>
Reported-by: Andreas Christoforou <andreaschristofo@gmail.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Our msg priorities became an rbtree as of d6629859b3 ("ipc/mqueue:
improve performance of send/recv"). However, consuming a msg in
msg_get() remains logarithmic (still being better than the case before
of course). By applying well known techniques to cache pointers we can
have the node with the highest priority in O(1), which is specially nice
for the rt cases. Furthermore, some callers can call msg_get() in a
loop.
A new msg_tree_erase() helper is also added to encapsulate the tree
removal and node_cache game. Passes ltp mq testcases.
Link: http://lkml.kernel.org/r/20190321190216.1719-2-dave@stgolabs.net
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We already store the current task fo the new waiter before calling
wq_sleep() in both send and recv paths. Trivially remove the redundant
assignment.
Link: http://lkml.kernel.org/r/20190321190216.1719-1-dave@stgolabs.net
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull vfs mount infrastructure updates from Al Viro:
"The rest of core infrastructure; no new syscalls in that pile, but the
old parts are switched to new infrastructure. At that point
conversions of individual filesystems can happen independently; some
are done here (afs, cgroup, procfs, etc.), there's also a large series
outside of that pile dealing with NFS (quite a bit of option-parsing
stuff is getting used there - it's one of the most convoluted
filesystems in terms of mount-related logics), but NFS bits are the
next cycle fodder.
It got seriously simplified since the last cycle; documentation is
probably the weakest bit at the moment - I considered dropping the
commit introducing Documentation/filesystems/mount_api.txt (cutting
the size increase by quarter ;-), but decided that it would be better
to fix it up after -rc1 instead.
That pile allows to do followup work in independent branches, which
should make life much easier for the next cycle. fs/super.c size
increase is unpleasant; there's a followup series that allows to
shrink it considerably, but I decided to leave that until the next
cycle"
* 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (41 commits)
afs: Use fs_context to pass parameters over automount
afs: Add fs_context support
vfs: Add some logging to the core users of the fs_context log
vfs: Implement logging through fs_context
vfs: Provide documentation for new mount API
vfs: Remove kern_mount_data()
hugetlbfs: Convert to fs_context
cpuset: Use fs_context
kernfs, sysfs, cgroup, intel_rdt: Support fs_context
cgroup: store a reference to cgroup_ns into cgroup_fs_context
cgroup1_get_tree(): separate "get cgroup_root to use" into a separate helper
cgroup_do_mount(): massage calling conventions
cgroup: stash cgroup_root reference into cgroup_fs_context
cgroup2: switch to option-by-option parsing
cgroup1: switch to option-by-option parsing
cgroup: take options parsing into ->parse_monolithic()
cgroup: fold cgroup1_mount() into cgroup1_get_tree()
cgroup: start switching to fs_context
ipc: Convert mqueue fs to fs_context
proc: Add fs_context support to procfs
...
Convert the mqueue filesystem to use the filesystem context stuff.
Notes:
(1) The relevant ipc namespace is selected in when the context is
initialised (and it defaults to the current task's ipc namespace).
The caller can override this before calling vfs_get_tree().
(2) Rather than simply calling kern_mount_data(), mq_init_ns() and
mq_internal_mount() create a context, adjust it and then do the rest
of the mount procedure.
(3) The lazy mqueue mounting on creation of a new namespace is retained
from a previous patch, but the avoidance of sget() if no superblock
yet exists is reverted and the superblock is again keyed on the
namespace pointer.
Yes, there was a performance gain in not searching the superblock
hash, but it's only paid once per ipc namespace - and only if someone
uses mqueue within that namespace, so I'm not sure it's worth it,
especially as calling sget() allows avoidance of recursion.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
A lot of system calls that pass a time_t somewhere have an implementation
using a COMPAT_SYSCALL_DEFINEx() on 64-bit architectures, and have
been reworked so that this implementation can now be used on 32-bit
architectures as well.
The missing step is to redefine them using the regular SYSCALL_DEFINEx()
to get them out of the compat namespace and make it possible to build them
on 32-bit architectures.
Any system call that ends in 'time' gets a '32' suffix on its name for
that version, while the others get a '_time32' suffix, to distinguish
them from the normal version, which takes a 64-bit time argument in the
future.
In this step, only 64-bit architectures are changed, doing this rename
first lets us avoid touching the 32-bit architectures twice.
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Pull timekeeping updates from Thomas Gleixner:
"The timers and timekeeping departement provides:
- Another large y2038 update with further preparations for providing
the y2038 safe timespecs closer to the syscalls.
- An overhaul of the SHCMT clocksource driver
- SPDX license identifier updates
- Small cleanups and fixes all over the place"
* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (31 commits)
tick/sched : Remove redundant cpu_online() check
clocksource/drivers/dw_apb: Add reset control
clocksource: Remove obsolete CLOCKSOURCE_OF_DECLARE
clocksource/drivers: Unify the names to timer-* format
clocksource/drivers/sh_cmt: Add R-Car gen3 support
dt-bindings: timer: renesas: cmt: document R-Car gen3 support
clocksource/drivers/sh_cmt: Properly line-wrap sh_cmt_of_table[] initializer
clocksource/drivers/sh_cmt: Fix clocksource width for 32-bit machines
clocksource/drivers/sh_cmt: Fixup for 64-bit machines
clocksource/drivers/sh_tmu: Convert to SPDX identifiers
clocksource/drivers/sh_mtu2: Convert to SPDX identifiers
clocksource/drivers/sh_cmt: Convert to SPDX identifiers
clocksource/drivers/renesas-ostm: Convert to SPDX identifiers
clocksource: Convert to using %pOFn instead of device_node.name
tick/broadcast: Remove redundant check
RISC-V: Request newstat syscalls
y2038: signal: Change rt_sigtimedwait to use __kernel_timespec
y2038: socket: Change recvmmsg to use __kernel_timespec
y2038: sched: Change sched_rr_get_interval to use __kernel_timespec
y2038: utimes: Rework #ifdef guards for compat syscalls
...
Linus recently observed that if we did not worry about the padding
member in struct siginfo it is only about 48 bytes, and 48 bytes is
much nicer than 128 bytes for allocating on the stack and copying
around in the kernel.
The obvious thing of only adding the padding when userspace is
including siginfo.h won't work as there are sigframe definitions in
the kernel that embed struct siginfo.
So split siginfo in two; kernel_siginfo and siginfo. Keeping the
traditional name for the userspace definition. While the version that
is used internally to the kernel and ultimately will not be padded to
128 bytes is called kernel_siginfo.
The definition of struct kernel_siginfo I have put in include/signal_types.h
A set of buildtime checks has been added to verify the two structures have
the same field offsets.
To make it easy to verify the change kernel_siginfo retains the same
size as siginfo. The reduction in size comes in a following change.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Christoph Hellwig suggested a slightly different path for handling
backwards compatibility with the 32-bit time_t based system calls:
Rather than simply reusing the compat_sys_* entry points on 32-bit
architectures unchanged, we get rid of those entry points and the
compat_time types by renaming them to something that makes more sense
on 32-bit architectures (which don't have a compat mode otherwise),
and then share the entry points under the new name with the 64-bit
architectures that use them for implementing the compatibility.
The following types and interfaces are renamed here, and moved
from linux/compat_time.h to linux/time32.h:
old new
--- ---
compat_time_t old_time32_t
struct compat_timeval struct old_timeval32
struct compat_timespec struct old_timespec32
struct compat_itimerspec struct old_itimerspec32
ns_to_compat_timeval() ns_to_old_timeval32()
get_compat_itimerspec64() get_old_itimerspec32()
put_compat_itimerspec64() put_old_itimerspec32()
compat_get_timespec64() get_old_timespec32()
compat_put_timespec64() put_old_timespec32()
As we already have aliases in place, this patch addresses only the
instances that are relevant to the system call interface in particular,
not those that occur in device drivers and other modules. Those
will get handled separately, while providing the 64-bit version
of the respective interfaces.
I'm not renaming the timex, rusage and itimerval structures, as we are
still debating what the new interface will look like, and whether we
will need a replacement at all.
This also doesn't change the names of the syscall entry points, which can
be done more easily when we actually switch over the 32-bit architectures
to use them, at that point we need to change COMPAT_SYSCALL_DEFINEx to
SYSCALL_DEFINEx with a new name, e.g. with a _time32 suffix.
Suggested-by: Christoph Hellwig <hch@infradead.org>
Link: https://lore.kernel.org/lkml/20180705222110.GA5698@infradead.org/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Three ipc syscalls (mq_timedsend, mq_timedreceive and and semtimedop)
take a timespec argument. After we move 32-bit architectures over to
useing 64-bit time_t based syscalls, we need seperate entry points for
the old 32-bit based interfaces.
This changes the #ifdef guards for the existing 32-bit compat syscalls
to check for CONFIG_COMPAT_32BIT_TIME instead, which will then be
enabled on all existing 32-bit architectures.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
This is a preparatation for changing over __kernel_timespec to 64-bit
times, which involves assigning new system call numbers for mq_timedsend(),
mq_timedreceive() and semtimedop() for compatibility with future y2038
proof user space.
The existing ABIs will remain available through compat code.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
This reverts commit 36735a6a2b.
Aleksa Sarai <asarai@suse.de> writes:
> [REGRESSION v4.16-rc6] [PATCH] mqueue: forbid unprivileged user access to internal mount
>
> Felix reported weird behaviour on 4.16.0-rc6 with regards to mqueue[1],
> which was introduced by 36735a6a2b ("mqueue: switch to on-demand
> creation of internal mount").
>
> Basically, the reproducer boils down to being able to mount mqueue if
> you create a new user namespace, even if you don't unshare the IPC
> namespace.
>
> Previously this was not possible, and you would get an -EPERM. The mount
> is the *host* mqueue mount, which is being cached and just returned from
> mqueue_mount(). To be honest, I'm not sure if this is safe or not (or if
> it was intentional -- since I'm not familiar with mqueue).
>
> To me it looks like there is a missing permission check. I've included a
> patch below that I've compile-tested, and should block the above case.
> Can someone please tell me if I'm missing something? Is this actually
> safe?
>
> [1]: https://github.com/docker/docker/issues/36674
The issue is a lot deeper than a missing permission check. sb->s_user_ns
was is improperly set as well. So in addition to the filesystem being
mounted when it should not be mounted, so things are not allow that should
be.
We are practically to the release of 4.16 and there is no agreement between
Al Viro and myself on what the code should looks like to fix things properly.
So revert the code to what it was before so that we can take our time
and discuss this properly.
Fixes: 36735a6a2b ("mqueue: switch to on-demand creation of internal mount")
Reported-by: Felix Abecassis <fabecassis@nvidia.com>
Reported-by: Aleksa Sarai <asarai@suse.de>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This is the mindless scripted replacement of kernel use of POLL*
variables as described by Al, done by this script:
for V in IN OUT PRI ERR RDNORM RDBAND WRNORM WRBAND HUP RDHUP NVAL MSG; do
L=`git grep -l -w POLL$V | grep -v '^t' | grep -v /um/ | grep -v '^sa' | grep -v '/poll.h$'|grep -v '^D'`
for f in $L; do sed -i "-es/^\([^\"]*\)\(\<POLL$V\>\)/\\1E\\2/" $f; done
done
with de-mangling cleanups yet to come.
NOTE! On almost all architectures, the EPOLL* constants have the same
values as the POLL* constants do. But they keyword here is "almost".
For various bad reasons they aren't the same, and epoll() doesn't
actually work quite correctly in some cases due to this on Sparc et al.
The next patch from Al will sort out the final differences, and we
should be all done.
Scripted-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Previous behavior added tasks to the work queue using the static_prio
value instead of the dynamic priority value in prio. This caused RT tasks
to be added to the work queue in a FIFO manner rather than by priority.
Normal tasks were handled by priority.
This fix utilizes the dynamic priority of the task to ensure that both RT
and normal tasks are added to the work queue in priority order. Utilizing
the dynamic priority (prio) rather than the base priority (normal_prio)
was chosen to ensure that if a task had a boosted priority when it was
added to the work queue, it would be woken sooner to to ensure that it
releases any other locks it may be holding in a more timely manner. It is
understood that the task could have a lower priority when it wakes than
when it was added to the queue in this (unlikely) case.
Link: http://lkml.kernel.org/r/1513006652-7014-1-git-send-email-jhaws@sdl.usu.edu
Signed-off-by: Jonathan Haws <jhaws@sdl.usu.edu>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Reviewed-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Deepa Dinamani <deepa.kernel@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull mqueue/bpf vfs cleanups from Al Viro:
"mqueue and bpf go through rather painful and similar contortions to
create objects in their dentry trees. Provide a primitive for doing
that without abusing ->mknod(), switch bpf and mqueue to it.
Another mqueue-related thing that has ended up in that branch is
on-demand creation of internal mount (based upon the work of Giuseppe
Scrivano)"
* 'work.mqueue' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
mqueue: switch to on-demand creation of internal mount
tidy do_mq_open() up a bit
mqueue: clean prepare_open() up
do_mq_open(): move all work prior to dentry_open() into a helper
mqueue: fold mq_attr_ok() into mqueue_get_inode()
move dentry_open() calls up into do_mq_open()
mqueue: switch to vfs_mkobj(), quit abusing ->d_fsdata
bpf_obj_do_pin(): switch to vfs_mkobj(), quit abusing ->mknod()
new primitive: vfs_mkobj()
Pull poll annotations from Al Viro:
"This introduces a __bitwise type for POLL### bitmap, and propagates
the annotations through the tree. Most of that stuff is as simple as
'make ->poll() instances return __poll_t and do the same to local
variables used to hold the future return value'.
Some of the obvious brainos found in process are fixed (e.g. POLLIN
misspelled as POLL_IN). At that point the amount of sparse warnings is
low and most of them are for genuine bugs - e.g. ->poll() instance
deciding to return -EINVAL instead of a bitmap. I hadn't touched those
in this series - it's large enough as it is.
Another problem it has caught was eventpoll() ABI mess; select.c and
eventpoll.c assumed that corresponding POLL### and EPOLL### were
equal. That's true for some, but not all of them - EPOLL### are
arch-independent, but POLL### are not.
The last commit in this series separates userland POLL### values from
the (now arch-independent) kernel-side ones, converting between them
in the few places where they are copied to/from userland. AFAICS, this
is the least disruptive fix preserving poll(2) ABI and making epoll()
work on all architectures.
As it is, it's simply broken on sparc - try to give it EPOLLWRNORM and
it will trigger only on what would've triggered EPOLLWRBAND on other
architectures. EPOLLWRBAND and EPOLLRDHUP, OTOH, are never triggered
at all on sparc. With this patch they should work consistently on all
architectures"
* 'misc.poll' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (37 commits)
make kernel-side POLL... arch-independent
eventpoll: no need to mask the result of epi_item_poll() again
eventpoll: constify struct epoll_event pointers
debugging printk in sg_poll() uses %x to print POLL... bitmap
annotate poll(2) guts
9p: untangle ->poll() mess
->si_band gets POLL... bitmap stored into a user-visible long field
ring_buffer_poll_wait() return value used as return value of ->poll()
the rest of drivers/*: annotate ->poll() instances
media: annotate ->poll() instances
fs: annotate ->poll() instances
ipc, kernel, mm: annotate ->poll() instances
net: annotate ->poll() instances
apparmor: annotate ->poll() instances
tomoyo: annotate ->poll() instances
sound: annotate ->poll() instances
acpi: annotate ->poll() instances
crypto: annotate ->poll() instances
block: annotate ->poll() instances
x86: annotate ->poll() instances
...
Call clear_siginfo to ensure stack allocated siginfos are fully
initialized before being passed to the signal sending functions.
This ensures that if there is the kind of confusion documented by
TRAP_FIXME, FPE_FIXME, or BUS_FIXME the kernel won't send unitialized
data to userspace when the kernel generates a signal with SI_USER but
the copy to userspace assumes it is a different kind of signal, and
different fields are initialized.
This also prepares the way for turning copy_siginfo_to_user
into a copy_to_user, by removing the need in many cases to perform
a field by field copy simply to skip the uninitialized fields.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Instead of doing that upon each ipcns creation, we do that the first
time mq_open(2) or mqueue mount is done in an ipcns. What's more,
doing that allows to get rid of mount_ns() use - we can go with
considerably cheaper mount_nodev(), avoiding the loop over all
mqueue superblock instances; ipcns->mq_mnt is used to locate preexisting
instance in O(1) time instead of O(instances) mount_ns() would've
cost us.
Based upon the version by Giuseppe Scrivano <gscrivan@redhat.com>; I've
added handling of userland mqueue mounts (original had been broken in
that area) and added a switch to mount_nodev().
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Linus Torvalds
Rik van Riel
Christian Brauner
Zhengchao Shao
Jingyu Wang
Hangyu Hua
Yu Zhe
Waiman Long
Muchun Song
Alexey Gladkov
Varad Gautam
Christian Brauner
Oleg Nesterov
Somala Swaraj
Manfred Spraul
Davidlohr Bueso
Markus Elfring
Al Viro
Kees Cook
Li Rongqing
David Howells
Arnd Bergmann
Eric W. Biederman
Jonathan Haws