net: fix sk_forward_alloc corruption

[Eric Dumazet]

From: Eric Dumazet <eric.dumazet@xxxxxxxxx>

[ Upstream commit: 9d410c796067686b1e032d54ce475b7055537138 ]

On UDP sockets, we must call skb_free_datagram() with socket locked,
or risk sk_forward_alloc corruption. This requirement is not respected
in SUNRPC.

Add a convenient helper, skb_free_datagram_locked() and use it in SUNRPC

Reported-by: Francis Moreau <francis.moro@xxxxxxxxx>
Signed-off-by: Eric Dumazet <eric.dumazet@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
---
 include/linux/skbuff.h |    2 ++
 net/core/datagram.c    |   10 +++++++++-
 net/ipv4/udp.c         |    4 +---
 net/ipv6/udp.c         |    4 +---
 net/sunrpc/svcsock.c   |   10 +++++-----
 5 files changed, 18 insertions(+), 12 deletions(-)

--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1761,6 +1761,8 @@ extern int	       skb_copy_datagram_cons
 						     int to_offset,
 						     int size);
 extern void	       skb_free_datagram(struct sock *sk, struct sk_buff *skb);
+extern void	       skb_free_datagram_locked(struct sock *sk,
+						struct sk_buff *skb);
 extern int	       skb_kill_datagram(struct sock *sk, struct sk_buff *skb,
 					 unsigned int flags);
 extern __wsum	       skb_checksum(const struct sk_buff *skb, int offset,
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -223,6 +223,15 @@ void skb_free_datagram(struct sock *sk, 
 	consume_skb(skb);
 	sk_mem_reclaim_partial(sk);
 }
+EXPORT_SYMBOL(skb_free_datagram);
+
+void skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb)
+{
+	lock_sock(sk);
+	skb_free_datagram(sk, skb);
+	release_sock(sk);
+}
+EXPORT_SYMBOL(skb_free_datagram_locked);
 
 /**
  *	skb_kill_datagram - Free a datagram skbuff forcibly
@@ -749,5 +758,4 @@ unsigned int datagram_poll(struct file *
 EXPORT_SYMBOL(datagram_poll);
 EXPORT_SYMBOL(skb_copy_and_csum_datagram_iovec);
 EXPORT_SYMBOL(skb_copy_datagram_iovec);
-EXPORT_SYMBOL(skb_free_datagram);
 EXPORT_SYMBOL(skb_recv_datagram);
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -987,9 +987,7 @@ try_again:
 		err = ulen;
 
 out_free:
-	lock_sock(sk);
-	skb_free_datagram(sk, skb);
-	release_sock(sk);
+	skb_free_datagram_locked(sk, skb);
 out:
 	return err;
 
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -288,9 +288,7 @@ try_again:
 		err = ulen;
 
 out_free:
-	lock_sock(sk);
-	skb_free_datagram(sk, skb);
-	release_sock(sk);
+	skb_free_datagram_locked(sk, skb);
 out:
 	return err;
 
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -110,7 +110,7 @@ static void svc_release_skb(struct svc_r
 		rqstp->rq_xprt_ctxt = NULL;
 
 		dprintk("svc: service %p, releasing skb %p\n", rqstp, skb);
-		skb_free_datagram(svsk->sk_sk, skb);
+		skb_free_datagram_locked(svsk->sk_sk, skb);
 	}
 }
 
@@ -537,7 +537,7 @@ static int svc_udp_recvfrom(struct svc_r
 			printk("rpcsvc: received unknown control message:"
 			       "%d/%d\n",
 			       cmh->cmsg_level, cmh->cmsg_type);
-		skb_free_datagram(svsk->sk_sk, skb);
+		skb_free_datagram_locked(svsk->sk_sk, skb);
 		return 0;
 	}
 	svc_udp_get_dest_address(rqstp, cmh);
@@ -548,18 +548,18 @@ static int svc_udp_recvfrom(struct svc_r
 		if (csum_partial_copy_to_xdr(&rqstp->rq_arg, skb)) {
 			local_bh_enable();
 			/* checksum error */
-			skb_free_datagram(svsk->sk_sk, skb);
+			skb_free_datagram_locked(svsk->sk_sk, skb);
 			return 0;
 		}
 		local_bh_enable();
-		skb_free_datagram(svsk->sk_sk, skb);
+		skb_free_datagram_locked(svsk->sk_sk, skb);
 	} else {
 		/* we can use it in-place */
 		rqstp->rq_arg.head[0].iov_base = skb->data +
 			sizeof(struct udphdr);
 		rqstp->rq_arg.head[0].iov_len = len;
 		if (skb_checksum_complete(skb)) {
-			skb_free_datagram(svsk->sk_sk, skb);
+			skb_free_datagram_locked(svsk->sk_sk, skb);
 			return 0;
 		}
 		rqstp->rq_xprt_ctxt = skb;



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