Merge branch 'af_unix_MSG_PEEK'

Aaron Conole says:

====================
af_unix: return data from multiple SKBs on recv() with MSG_PEEK flag

This patch set implements a bugfix for kernel.org bugzilla #12323, allowing
MSG_PEEK to return all queued data on the unix domain socket, not just the
data contained in a single SKB.

This is the v3 version of this patch, which includes a suggested modification
by Eric Dumazet to convert the unix_sk() conversion macro to a static inline
function. These patches are independent and can be applied separately.

This set was tested over a 24-hour period, utilizing a loop continually
executing the bugzilla issue attached python code. It was instrumented with
a pr_err_once() ([   13.798683] unix: went there at least one time).

v2->v3:
 - Added Eric Dumazet's suggestion for #define to static inline
 - Fixed an issue calling unix_state_lock() with an invalid argument

v3->v4:
 - Eliminated an XXX comment
 - Changed from goto unlock to explicit unix_state_unlock() and break
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/af_unix.h

@@ -63,7 +63,11 @@ struct unix_sock {
 #define UNIX_GC_MAYBE_CYCLE	1
 	struct socket_wq	peer_wq;
 };
-#define unix_sk(__sk) ((struct unix_sock *)__sk)
+
+static inline struct unix_sock *unix_sk(struct sock *sk)
+{
+	return (struct unix_sock *)sk;
+}
 
 #define peer_wait peer_wq.wait
 

net/unix/af_unix.c

@@ -2179,8 +2179,21 @@ static int unix_stream_read_generic(struct unix_stream_read_state *state)
 			if (UNIXCB(skb).fp)
 				scm.fp = scm_fp_dup(UNIXCB(skb).fp);
 
-			sk_peek_offset_fwd(sk, chunk);
+			if (skip) {
+				sk_peek_offset_fwd(sk, chunk);
+				skip -= chunk;
+			}
 
+			if (UNIXCB(skb).fp)
+				break;
+
+			last = skb;
+			last_len = skb->len;
+			unix_state_lock(sk);
+			skb = skb_peek_next(skb, &sk->sk_receive_queue);
+			if (skb)
+				goto again;
+			unix_state_unlock(sk);
 			break;
 		}
 	} while (size);