llc: Fix race condition in llc_ui_recvmsg

There is a race on sk_receive_queue between llc_ui_recvmsg and
sock_queue_rcv_skb.

Our current solution is to protect skb_eat in llc_ui_recvmsg
with the queue spinlock.

Signed-off-by: Radu Iliescu <riliescu@ixiacom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 0 deletions

diff --git a/net/llc/af_llc.c b/net/llc/af_llc.c
index a18e6c3d36e3..b9bef2c75026 100644
--- a/net/llc/af_llc.c
+++ b/net/llc/af_llc.c
@@ -713,6 +713,7 @@ static int llc_ui_recvmsg(struct kiocb *iocb, struct socket *sock,
         struct sk_buff *skb = NULL;
         struct sock *sk = sock->sk;
         struct llc_sock *llc = llc_sk(sk);
+        unsigned long cpu_flags;
         size_t copied = 0;
         u32 peek_seq = 0;
         u32 *seq;
@@ -838,7 +839,9 @@ static int llc_ui_recvmsg(struct kiocb *iocb, struct socket *sock,
                         goto copy_uaddr;
 
                 if (!(flags & MSG_PEEK)) {
+                        spin_lock_irqsave(&sk->sk_receive_queue.lock, cpu_flags);
                         sk_eat_skb(sk, skb, 0);
+                        spin_unlock_irqrestore(&sk->sk_receive_queue.lock, cpu_flags);
                         *seq = 0;
                 }
 
@@ -859,7 +862,9 @@ copy_uaddr:
                 llc_cmsg_rcv(msg, skb);
 
         if (!(flags & MSG_PEEK)) {
+                        spin_lock_irqsave(&sk->sk_receive_queue.lock, cpu_flags);
                         sk_eat_skb(sk, skb, 0);
+                        spin_unlock_irqrestore(&sk->sk_receive_queue.lock, cpu_flags);
                         *seq = 0;
         }