This fixes 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 <[EMAIL PROTECTED]>
---
kernel/cgroup.c | 1 -
1 files changed, 0 insertions(+), 1 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 35eebd5..358e775 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);
--
1.5.4.rc3
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