The patch titled
cgroup: catch bad css refcnt at css_put
has been added to the -mm tree. Its filename is
cgroup-catch-bad-css-refcnt-at-css_put.patch
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------------------------------------------------------
Subject: cgroup: catch bad css refcnt at css_put
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
__css_put() doesn't check a bug as refcnt goes to minus.
I think it should be caught. This patch adds a check for it.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Paul Menage <menage@xxxxxxxxxx>
Cc: Li Zefan <lizf@xxxxxxxxxxxxxx>
Cc: Balbir Singh <balbir@xxxxxxxxxx>
Cc: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/cgroup.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff -puN kernel/cgroup.c~cgroup-catch-bad-css-refcnt-at-css_put kernel/cgroup.c
--- a/kernel/cgroup.c~cgroup-catch-bad-css-refcnt-at-css_put
+++ a/kernel/cgroup.c
@@ -3708,8 +3708,10 @@ static void check_for_release(struct cgr
void __css_put(struct cgroup_subsys_state *css)
{
struct cgroup *cgrp = css->cgroup;
+ int val;
rcu_read_lock();
- if (atomic_dec_return(&css->refcnt) == 1) {
+ val = atomic_dec_return(&css->refcnt);
+ if (val == 1) {
if (notify_on_release(cgrp)) {
set_bit(CGRP_RELEASABLE, &cgrp->flags);
check_for_release(cgrp);
@@ -3717,6 +3719,7 @@ void __css_put(struct cgroup_subsys_stat
cgroup_wakeup_rmdir_waiter(cgrp);
}
rcu_read_unlock();
+ WARN_ON_ONCE(val < 1);
}
/*
_
Patches currently in -mm which might be from kamezawa.hiroyu@xxxxxxxxxxxxxx are
memcg-fix-refcnt-goes-to-minus.patch
cgroup-catch-bad-css-refcnt-at-css_put.patch
memcg-some-modification-to-softlimit-under-hierarchical-memory-reclaim.patch
memcg-reduce-check-for-softlimit-excess.patch
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