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device_cgroup: fix RCU imbalance in error case 

When dev_exception_add() returns an error (due to a failed memory
allocation), make sure that we move the RCU preemption count back to where
it was before we were called. We dropped the RCU read lock inside the loop
body, so we can't just "break".

sparse complains about this, too:

$ make -s C=2 security/device_cgroup.o
./include/linux/rcupdate.h:647:9: warning: context imbalance in
'propagate_exception' - unexpected unlock

Fixes: d591fb5661 ("device_cgroup: simplify cgroup tree walk in propagate_exception()")
Cc: stable@vger.kernel.org
Signed-off-by: Jann Horn <jannh@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Jann Horn 2019-03-19 02:36:59 +01:00 committed by Tejun Heo
parent 9e98c678c2
commit 0fcc4c8c04
1 changed files with 1 additions and 1 deletions
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2
security/device_cgroup.c
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@ -560,7 +560,7 @@ static int propagate_exception(struct dev_cgroup *devcg_root,
devcg->behavior == DEVCG_DEFAULT_ALLOW) { devcg->behavior == DEVCG_DEFAULT_ALLOW) {
rc = dev_exception_add(devcg, ex); rc = dev_exception_add(devcg, ex);
if (rc) if (rc)
break; return rc;
} else { } else {
/* /*
* in the other possible cases: * in the other possible cases: