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authorLi Zefan <lizf@cn.fujitsu.com>2008-11-06 15:53:32 -0500
committerLinus Torvalds <torvalds@linux-foundation.org>2008-11-06 18:41:19 -0500
commit24eb089950ce44603b30a3145a2c8520e2b55bb1 (patch)
tree3cccd3e15589c693c8c4e6484a938d2343ef1abc
parentb41ad14c30acf023d09ac064096a4cf41248ce46 (diff)
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>
-rw-r--r--kernel/cgroup.c1
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)
2497 list_del(&cgrp->sibling); 2497 list_del(&cgrp->sibling);
2498 spin_lock(&cgrp->dentry->d_lock); 2498 spin_lock(&cgrp->dentry->d_lock);
2499 d = dget(cgrp->dentry); 2499 d = dget(cgrp->dentry);
2500 cgrp->dentry = NULL;
2501 spin_unlock(&d->d_lock); 2500 spin_unlock(&d->d_lock);
2502 2501
2503 cgroup_d_remove_dir(d); 2502 cgroup_d_remove_dir(d);