4.9-stable review patch. If anyone has any objections, please let me know.
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From: Cong Wang xiyou.wangcong@gmail.com
[ Upstream commit cc4dfb7f70a344f24c1c71e298deea0771dadcb2 ]
When a rds sock is bound, it is inserted into the bind_hash_table which is protected by RCU. But when releasing rds sock, after it is removed from this hash table, it is freed immediately without respecting RCU grace period. This could cause some use-after-free as reported by syzbot.
Mark the rds sock with SOCK_RCU_FREE before inserting it into the bind_hash_table, so that it would be always freed after a RCU grace period.
The other problem is in rds_find_bound(), the rds sock could be freed in between rhashtable_lookup_fast() and rds_sock_addref(), so we need to extend RCU read lock protection in rds_find_bound() to close this race condition.
Reported-and-tested-by: syzbot+8967084bcac563795dc6@syzkaller.appspotmail.com Reported-by: syzbot+93a5839deb355537440f@syzkaller.appspotmail.com Cc: Sowmini Varadhan sowmini.varadhan@oracle.com Cc: Santosh Shilimkar santosh.shilimkar@oracle.com Cc: rds-devel@oss.oracle.com Signed-off-by: Cong Wang xiyou.wangcong@gmail.com Acked-by: Santosh Shilimkar santosh.shilimkar@oarcle.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/rds/bind.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
--- a/net/rds/bind.c +++ b/net/rds/bind.c @@ -60,11 +60,13 @@ struct rds_sock *rds_find_bound(__be32 a u64 key = ((u64)addr << 32) | port; struct rds_sock *rs;
- rs = rhashtable_lookup_fast(&bind_hash_table, &key, ht_parms); + rcu_read_lock(); + rs = rhashtable_lookup(&bind_hash_table, &key, ht_parms); if (rs && !sock_flag(rds_rs_to_sk(rs), SOCK_DEAD)) rds_sock_addref(rs); else rs = NULL; + rcu_read_unlock();
rdsdebug("returning rs %p for %pI4:%u\n", rs, &addr, ntohs(port)); @@ -157,6 +159,7 @@ int rds_bind(struct socket *sock, struct goto out; }
+ sock_set_flag(sk, SOCK_RCU_FREE); ret = rds_add_bound(rs, sin->sin_addr.s_addr, &sin->sin_port); if (ret) goto out;