Merge branch 'af_unix-fix-inq_len-update-issue'

Jianyu Li says:

====================
af_unix: Fix inq_len update issue

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

This series fix the problem that inq_len is inconsistent with
actual remaining byte count when only part of a skb is consumed.
====================

Link: https://patch.msgid.link/20260601113640.231897-1-jianyu.li@mediatek.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

2 files changed, 58 insertions, 7 deletions

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index dc71ed79be4a..0d9cd977c7b7 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 @@ unlock:
 				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);
 
diff --git a/tools/testing/selftests/net/af_unix/scm_inq.c b/tools/testing/selftests/net/af_unix/scm_inq.c
index 3a86be9bda17..6268b5bf50be 100644
--- a/tools/testing/selftests/net/af_unix/scm_inq.c
+++ b/tools/testing/selftests/net/af_unix/scm_inq.c
@@ -8,8 +8,9 @@
 
 #include "kselftest_harness.h"
 
-#define NR_CHUNKS	100
-#define MSG_LEN		256
+#define NR_CHUNKS		100
+#define MSG_LEN			256
+#define NR_PARTIAL_READS	3
 
 FIXTURE(scm_inq)
 {
@@ -120,4 +121,53 @@ TEST_F(scm_inq, basic)
 	recv_chunks(_metadata, self);
 }
 
+TEST_F(scm_inq, partial_read)
+{
+	char buf[MSG_LEN * NR_PARTIAL_READS] = {};
+	char cmsg_buf[CMSG_SPACE(sizeof(int))];
+	struct msghdr msg = {};
+	struct iovec iov = {};
+	struct cmsghdr *cmsg;
+	int err, inq, ret, i;
+	int remain;
+
+	err = setsockopt(self->fd[1], SOL_SOCKET, SO_INQ, &(int){1}, sizeof(int));
+	if (variant->type != SOCK_STREAM) {
+		ASSERT_EQ(-ENOPROTOOPT, -errno);
+		return;
+	}
+	ASSERT_EQ(0, err);
+
+	ret = send(self->fd[0], buf, sizeof(buf), 0);
+	ASSERT_EQ(sizeof(buf), ret);
+
+	msg.msg_iov = &iov;
+	msg.msg_iovlen = 1;
+	msg.msg_control = cmsg_buf;
+	msg.msg_controllen = sizeof(cmsg_buf);
+
+	iov.iov_base = buf;
+	iov.iov_len = MSG_LEN;
+
+	for (i = 0; i < NR_PARTIAL_READS; i++) {
+		remain = MSG_LEN * (NR_PARTIAL_READS - 1 - i);
+
+		memset(buf, 0, MSG_LEN);
+		memset(cmsg_buf, 0, sizeof(cmsg_buf));
+		ret = recvmsg(self->fd[1], &msg, 0);
+		ASSERT_EQ(MSG_LEN, ret);
+
+		cmsg = CMSG_FIRSTHDR(&msg);
+		ASSERT_NE(NULL, cmsg);
+		ASSERT_EQ(CMSG_LEN(sizeof(int)), cmsg->cmsg_len);
+		ASSERT_EQ(SOL_SOCKET, cmsg->cmsg_level);
+		ASSERT_EQ(SCM_INQ, cmsg->cmsg_type);
+		ASSERT_EQ(remain, *(int *)CMSG_DATA(cmsg));
+
+		ret = ioctl(self->fd[1], SIOCINQ, &inq);
+		ASSERT_EQ(0, ret);
+		ASSERT_EQ(remain, inq);
+	}
+}
+
 TEST_HARNESS_MAIN