diff options
| author | Cong Wang <xiyou.wangcong@gmail.com> | 2018-08-07 12:41:38 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-08-07 15:54:00 -0700 |
| commit | 0dcb82254d65f72333aa50ad626d1e9665ad093b (patch) | |
| tree | 0624bb5c365884b956d4abaf79d50e87a1406762 | |
| parent | 61ef4b07fcdc30535889990cf4229766502561cf (diff) | |
| download | linux-4.18.y-0dcb82254d65f72333aa50ad626d1e9665ad093b.tar.gz | |
llc: use refcount_inc_not_zero() for llc_sap_find()
llc_sap_put() decreases the refcnt before deleting sap
from the global list. Therefore, there is a chance
llc_sap_find() could find a sap with zero refcnt
in this global list.
Close this race condition by checking if refcnt is zero
or not in llc_sap_find(), if it is zero then it is being
removed so we can just treat it as gone.
Reported-by: <syzbot+278893f3f7803871f7ce@syzkaller.appspotmail.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | include/net/llc.h | 5 | ||||
| -rw-r--r-- | net/llc/llc_core.c | 4 |
2 files changed, 7 insertions, 2 deletions
diff --git a/include/net/llc.h b/include/net/llc.h index dc35f25eb679d..890a87318014d 100644 --- a/include/net/llc.h +++ b/include/net/llc.h @@ -116,6 +116,11 @@ static inline void llc_sap_hold(struct llc_sap *sap) refcount_inc(&sap->refcnt); } +static inline bool llc_sap_hold_safe(struct llc_sap *sap) +{ + return refcount_inc_not_zero(&sap->refcnt); +} + void llc_sap_close(struct llc_sap *sap); static inline void llc_sap_put(struct llc_sap *sap) diff --git a/net/llc/llc_core.c b/net/llc/llc_core.c index 89041260784c0..260b3dc1b4a2a 100644 --- a/net/llc/llc_core.c +++ b/net/llc/llc_core.c @@ -73,8 +73,8 @@ struct llc_sap *llc_sap_find(unsigned char sap_value) rcu_read_lock_bh(); sap = __llc_sap_find(sap_value); - if (sap) - llc_sap_hold(sap); + if (!sap || !llc_sap_hold_safe(sap)) + sap = NULL; rcu_read_unlock_bh(); return sap; } |