diff options
| author | Tejun Heo <tj@kernel.org> | 2022-12-07 16:53:15 -1000 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2022-12-08 10:40:58 -0800 |
| commit | fbf8321238bac04368f57af572e05a9c01347a0b (patch) | |
| tree | 3dc1ff4425dbc725bc6116e3dde8c76afc4f8837 /kernel/cgroup | |
| parent | 479174d402bcf60789106eedc4def3957c060bad (diff) | |
| download | linux-fbf8321238bac04368f57af572e05a9c01347a0b.tar.gz | |
memcg: Fix possible use-after-free in memcg_write_event_control()
memcg_write_event_control() accesses the dentry->d_name of the specified
control fd to route the write call. As a cgroup interface file can't be
renamed, it's safe to access d_name as long as the specified file is a
regular cgroup file. Also, as these cgroup interface files can't be
removed before the directory, it's safe to access the parent too.
Prior to 347c4a874710 ("memcg: remove cgroup_event->cft"), there was a
call to __file_cft() which verified that the specified file is a regular
cgroupfs file before further accesses. The cftype pointer returned from
__file_cft() was no longer necessary and the commit inadvertently
dropped the file type check with it allowing any file to slip through.
With the invarients broken, the d_name and parent accesses can now race
against renames and removals of arbitrary files and cause
use-after-free's.
Fix the bug by resurrecting the file type check in __file_cft(). Now
that cgroupfs is implemented through kernfs, checking the file
operations needs to go through a layer of indirection. Instead, let's
check the superblock and dentry type.
Signed-off-by: Tejun Heo <tj@kernel.org>
Fixes: 347c4a874710 ("memcg: remove cgroup_event->cft")
Cc: stable@kernel.org # v3.14+
Reported-by: Jann Horn <jannh@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/cgroup')
| -rw-r--r-- | kernel/cgroup/cgroup-internal.h | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/kernel/cgroup/cgroup-internal.h b/kernel/cgroup/cgroup-internal.h index fd4020835ec6c..367b0a42ada90 100644 --- a/kernel/cgroup/cgroup-internal.h +++ b/kernel/cgroup/cgroup-internal.h @@ -167,7 +167,6 @@ struct cgroup_mgctx { extern spinlock_t css_set_lock; extern struct cgroup_subsys *cgroup_subsys[]; extern struct list_head cgroup_roots; -extern struct file_system_type cgroup_fs_type; /* iterate across the hierarchies */ #define for_each_root(root) \ |