[PATCH net v3 1/2] af_unix: Fix inq_len update problem in partial read

[<jianyu.li@mediatek.com>]

From: Jianyu Li <jianyu.li@mediatek.com>

Currently inq_len is updated only when the whole skb is consumed.
If only part of the data is read, following SIOCINQ query would
get value greater than what actually left.

This change update inq_len timely in unix_stream_read_generic(),
and adjust unix_stream_read_skb() accordingly to prevent
repetitive update.

Fixes: f4e1fb04c123 ("af_unix: Use cached value for SOCK_STREAM in unix_inq_len().")
Signed-off-by: Jianyu Li <jianyu.li@mediatek.com>
---
v2: Improve lock usage in unix_stream_read_generic()
---
 net/unix/af_unix.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index dc71ed79be..0d9cd977c7 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -2886,7 +2886,7 @@ static int unix_stream_read_skb(struct sock *sk, skb_read_actor_t recv_actor)
 		return -EAGAIN;
 	}
 
-	WRITE_ONCE(u->inq_len, u->inq_len - skb->len);
+	WRITE_ONCE(u->inq_len, u->inq_len - unix_skb_len(skb));
 
 #if IS_ENABLED(CONFIG_AF_UNIX_OOB)
 	if (skb == u->oob_skb) {
@@ -3063,11 +3063,12 @@ static int unix_stream_read_generic(struct unix_stream_read_state *state,
 				unix_detach_fds(&scm, skb);
 			}
 
-			if (unix_skb_len(skb))
-				break;
-
 			spin_lock(&sk->sk_receive_queue.lock);
-			WRITE_ONCE(u->inq_len, u->inq_len - skb->len);
+			WRITE_ONCE(u->inq_len, u->inq_len - chunk);
+			if (unix_skb_len(skb)) {
+				spin_unlock(&sk->sk_receive_queue.lock);
+				break;
+			}
 			__skb_unlink(skb, &sk->sk_receive_queue);
 			spin_unlock(&sk->sk_receive_queue.lock);
 
-- 
2.45.2