The patch titled
cgroups: fix lock inconsistency in cgroup_clone()
has been added to the -mm tree. Its filename is
cgroups-fix-lock-inconsistency-in-cgroup_clone.patch
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------------------------------------------------------
Subject: cgroups: fix lock inconsistency in cgroup_clone()
From: Li Zefan <lizf@xxxxxxxxxxxxxx>
I fixed a bug in cgroup_clone() in Linus' tree ni commit 7b574b7
("cgroups: fix a race between cgroup_clone and umount") without noticing
there was a cleanup patch in -mm tree that should be rebased (now commit
104cbd5, "cgroups: use task_lock() for access tsk->cgroups safe in
cgroup_clone()"), thus resulted in lock inconsistency.
Signed-off-by: Li Zefan <lizf@xxxxxxxxxxxxxx>
Acked-by: Paul Menage <menage@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/cgroup.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
diff -puN kernel/cgroup.c~cgroups-fix-lock-inconsistency-in-cgroup_clone kernel/cgroup.c
--- a/kernel/cgroup.c~cgroups-fix-lock-inconsistency-in-cgroup_clone
+++ a/kernel/cgroup.c
@@ -2993,20 +2993,21 @@ int cgroup_clone(struct task_struct *tsk
mutex_unlock(&cgroup_mutex);
return 0;
}
- task_lock(tsk);
- cg = tsk->cgroups;
- parent = task_cgroup(tsk, subsys->subsys_id);
/* Pin the hierarchy */
- if (!atomic_inc_not_zero(&parent->root->sb->s_active)) {
+ if (!atomic_inc_not_zero(&root->sb->s_active)) {
/* We race with the final deactivate_super() */
mutex_unlock(&cgroup_mutex);
return 0;
}
/* Keep the cgroup alive */
+ task_lock(tsk);
+ parent = task_cgroup(tsk, subsys->subsys_id);
+ cg = tsk->cgroups;
get_css_set(cg);
task_unlock(tsk);
+
mutex_unlock(&cgroup_mutex);
/* Now do the VFS work to create a cgroup */
@@ -3045,7 +3046,7 @@ int cgroup_clone(struct task_struct *tsk
mutex_unlock(&inode->i_mutex);
put_css_set(cg);
- deactivate_super(parent->root->sb);
+ deactivate_super(root->sb);
/* The cgroup is still accessible in the VFS, but
* we're not going to try to rmdir() it at this
* point. */
@@ -3071,7 +3072,7 @@ int cgroup_clone(struct task_struct *tsk
mutex_lock(&cgroup_mutex);
put_css_set(cg);
mutex_unlock(&cgroup_mutex);
- deactivate_super(parent->root->sb);
+ deactivate_super(root->sb);
return ret;
}
_
Patches currently in -mm which might be from lizf@xxxxxxxxxxxxxx are
cgroups-use-hierarchy-mutex-in-creation-failure-path.patch
memcg-get-put-parents-at-create-free.patch
memcg-get-put-parents-at-create-free-fix.patch
memcg-fix-refcnt-handling-at-swapoff.patch
memcg-update-document-to-mention-swapoff-should-be-test.patch
memcg-null-pointer-dereference-at-rmdir-on-some-numa-systems-v2.patch
cgroups-fix-lock-inconsistency-in-cgroup_clone.patch
linux-next.patch
relax-ns_can_attach-checks-to-allow-attaching-to-grandchild-cgroups.patch
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