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| author | Li Zefan <lizf@cn.fujitsu.com> | 2008-11-06 12:53:32 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-11-06 15:41:19 -0800 |
| commit | 24eb089950ce44603b30a3145a2c8520e2b55bb1 (patch) | |
| tree | 3cccd3e15589c693c8c4e6484a938d2343ef1abc /kernel | |
| parent | b41ad14c30acf023d09ac064096a4cf41248ce46 (diff) | |
| download | linux-24eb089950ce44603b30a3145a2c8520e2b55bb1.tar.gz linux-24eb089950ce44603b30a3145a2c8520e2b55bb1.tar.bz2 linux-24eb089950ce44603b30a3145a2c8520e2b55bb1.zip | |
cgroups: fix invalid cgrp->dentry before cgroup has been completely removed
This fixes an oops when reading /proc/sched_debug.
A cgroup won't be removed completely until finishing cgroup_diput(), so we
shouldn't invalidate cgrp->dentry in cgroup_rmdir(). Otherwise, when a
group is being removed while cgroup_path() gets called, we may trigger
NULL dereference BUG.
The bug can be reproduced:
# cat test.sh
#!/bin/sh
mount -t cgroup -o cpu xxx /mnt
for (( ; ; ))
{
mkdir /mnt/sub
rmdir /mnt/sub
}
# ./test.sh &
# cat /proc/sched_debug
BUG: unable to handle kernel NULL pointer dereference at 00000038
IP: [<c045a47f>] cgroup_path+0x39/0x90
...
Call Trace:
[<c0420344>] ? print_cfs_rq+0x6e/0x75d
[<c0421160>] ? sched_debug_show+0x72d/0xc1e
...
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Paul Menage <menage@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: <stable@kernel.org> [2.6.26.x, 2.6.27.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/cgroup.c | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 35eebd5510c2..358e77564e6f 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -2497,7 +2497,6 @@ static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry) list_del(&cgrp->sibling); spin_lock(&cgrp->dentry->d_lock); d = dget(cgrp->dentry); - cgrp->dentry = NULL; spin_unlock(&d->d_lock); cgroup_d_remove_dir(d); |