Messages in this thread Patch in this message | | | Date | Thu, 30 Oct 2008 15:23:27 +0800 | From | Li Zefan <> | Subject | [PATCH] cgroup: fix invalid cgrp->dentry before cgroup has been completely removed |
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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 <lizf@cn.fujitsu.com> --- 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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