syzbot is reporting that tipc_udp_send_msg() is calling dst_cache_get() without preemption disabled [1]. Since b->media->send_msg() is called with RCU lock already held, we can also disable preemption at that point.
[1] https://syzkaller.appspot.com/bug?id=dc6352b92862eb79373fe03fdf9af5928753e057 Reported-by: syzbot+1a68504d96cd17b33...@syzkaller.appspotmail.com Signed-off-by: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp> --- net/tipc/bearer.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/net/tipc/bearer.c b/net/tipc/bearer.c index 34ca7b789eba..e5cf91665881 100644 --- a/net/tipc/bearer.c +++ b/net/tipc/bearer.c @@ -516,6 +516,7 @@ void tipc_bearer_xmit_skb(struct net *net, u32 bearer_id, struct tipc_msg *hdr = buf_msg(skb); struct tipc_bearer *b; + preempt_disable(); rcu_read_lock(); b = bearer_get(net, bearer_id); if (likely(b && (test_bit(0, &b->up) || msg_is_reset(hdr)))) { @@ -528,6 +529,7 @@ void tipc_bearer_xmit_skb(struct net *net, u32 bearer_id, kfree_skb(skb); } rcu_read_unlock(); + preempt_enable(); } /* tipc_bearer_xmit() -send buffer to destination over bearer @@ -543,6 +545,7 @@ void tipc_bearer_xmit(struct net *net, u32 bearer_id, if (skb_queue_empty(xmitq)) return; + preempt_disable(); rcu_read_lock(); b = bearer_get(net, bearer_id); if (unlikely(!b)) @@ -560,6 +563,7 @@ void tipc_bearer_xmit(struct net *net, u32 bearer_id, } } rcu_read_unlock(); + preempt_enable(); } /* tipc_bearer_bc_xmit() - broadcast buffers to all destinations @@ -574,6 +578,7 @@ void tipc_bearer_bc_xmit(struct net *net, u32 bearer_id, struct sk_buff *skb, *tmp; struct tipc_msg *hdr; + preempt_disable(); rcu_read_lock(); b = bearer_get(net, bearer_id); if (unlikely(!b || !test_bit(0, &b->up))) @@ -591,6 +596,7 @@ void tipc_bearer_bc_xmit(struct net *net, u32 bearer_id, b->media->send_msg(net, skb, b, dst); } rcu_read_unlock(); + preempt_enable(); } /** -- 2.18.2
