The patch titled
cgroups: fix invalid cgrp->dentry before cgroup has been completely removed
has been removed from the -mm tree. Its filename was
cgroups-fix-invalid-cgrp-dentry-before-cgroup-has-been-completely-removed.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: cgroups: fix invalid cgrp->dentry before cgroup has been completely removed
From: Li Zefan <lizf@xxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxx>
Acked-by: Paul Menage <menage@xxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: <stable@xxxxxxxxxx> [2.6.26.x, 2.6.27.x]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/cgroup.c | 1 -
1 file changed, 1 deletion(-)
diff -puN kernel/cgroup.c~cgroups-fix-invalid-cgrp-dentry-before-cgroup-has-been-completely-removed kernel/cgroup.c
--- a/kernel/cgroup.c~cgroups-fix-invalid-cgrp-dentry-before-cgroup-has-been-completely-removed
+++ a/kernel/cgroup.c
@@ -2497,7 +2497,6 @@ static int cgroup_rmdir(struct inode *un
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);
_
Patches currently in -mm which might be from lizf@xxxxxxxxxxxxxx are
linux-next.patch
freezer_cg-remove-task_lock-from-freezer_fork.patch
freezer_cg-disable-writing-freezerstate-of-root-cgroup.patch
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