Because rose_ioctl() accesses sk->sk_receive_queue
without holding a sk->sk_receive_queue.lock, it can
cause a race with rose_accept().
A use-after-free for skb occurs with the following flow.

rose_ioctl() -> skb_peek()
rose_accept() -> skb_dequeue() -> kfree_skb()

Add sk->sk_receive_queue.lock to rose_ioctl() to fix this issue.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Hyunwoo Kim <redacted>
---
v1 -> v2: Use sk->sk_receive_queue.lock instead of lock_sock.
v2 -> v3: Change spin_lock to spin_lock_irq
v3 -> v4: Delete old comments
---
 net/rose/af_rose.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/rose/af_rose.c b/net/rose/af_rose.c
index 0cc5a4e19900..ecb91ad4ce63 100644
--- a/net/rose/af_rose.c
+++ b/net/rose/af_rose.c

@@ -1315,9 +1315,11 @@ static int rose_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
 	case TIOCINQ: {
 		struct sk_buff *skb;
 		long amount = 0L;
-		/* These two are safe on a single CPU system as only user tasks fiddle here */
+
+		spin_lock_irq(&sk->sk_receive_queue.lock);
 		if ((skb = skb_peek(&sk->sk_receive_queue)) != NULL)
 			amount = skb->len;
+		spin_unlock_irq(&sk->sk_receive_queue.lock);
 		return put_user(amount, (unsigned int __user *) argp);
 	}
 

-- 
2.25.1