]> pilppa.com Git - linux-2.6-omap-h63xx.git/commitdiff
cgroups: fix invalid cgrp->dentry before cgroup has been completely removed
authorLi Zefan <lizf@cn.fujitsu.com>
Thu, 6 Nov 2008 20:53:32 +0000 (12:53 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Thu, 6 Nov 2008 23:41:19 +0000 (15:41 -0800)
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>
kernel/cgroup.c

index 35eebd5510c2165c6f8daa2cef1fecab9187d6d0..358e77564e6f8b0b4c3964a36da48cc3051d6e73 100644 (file)
@@ -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);