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[34.127.51.67]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3a0972efa00sm4003402a91.5.2026.09.24.00.16.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 24 Sep 2026 00:16:31 -0700 (PDT) From: Hui Peng To: kuniyu@amazon.com, edumazet@google.com, davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Hui Peng Subject: [PATCH net v2 1/2] af_unix: decrement u->inq_len when skipping unread OOB skb in manage_oob() Date: Thu, 24 Sep 2026 07:16:28 +0000 Message-ID: <20260924071629.2683160-2-benquike@gmail.com> X-Mailer: git-send-email 2.56.0.rc1.310.g51773c2048-goog In-Reply-To: <20260924071629.2683160-1-benquike@gmail.com> References: <20260924071629.2683160-1-benquike@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit When a normal in-band read on an AF_UNIX stream socket (without MSG_PEEK and without SO_OOBINLINE) encounters an unread u->oob_skb in manage_oob(), manage_oob() clears u->oob_skb, unlinks the 1-byte skb from sk->sk_receive_queue, and drops it with SKB_DROP_REASON_UNIX_SKIP_OOB without decrementing u->inq_len. Because queue_oob() incremented u->inq_len by 1 when queuing the OOB skb, u->inq_len remains permanently inflated by 1 byte for each skipped unread OOB skb, causing SIOCINQ / FIONREAD to report a stale positive byte count on an empty socket. Decrement u->inq_len by 1 when unlinking the unread OOB skb in manage_oob(). Tested in QEMU against Linux 7.3.0-rc3 by sending three 1-byte MSG_OOB packets interleaved with normal stream data on an AF_UNIX SOCK_STREAM socketpair and draining all in-band data via recv(): on the unfixed kernel, ioctl(SIOCINQ) reports 3 on the empty socket; with this patch applied, ioctl(SIOCINQ) reports 0. Fixes: f4e1fb04c123 ("af_unix: Use cached value for SOCK_STREAM in unix_inq_len().") Cc: stable@vger.kernel.org Assisted-by: LLM Signed-off-by: Hui Peng --- Changes in v2: - Split the manage_oob() and unix_stream_read_skb() fixes into a 2-patch series as requested by Kuniyuki Iwashima. - Update Fixes: tag to f4e1fb04c123 ("af_unix: Use cached value for SOCK_STREAM in unix_inq_len().") and clarify the commit message as noted by Sashiko. net/unix/af_unix.c | 1 + 1 file changed, 1 insertion(+) diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 42cffeafc8c1..1770af3c2684 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -2849,6 +2849,7 @@ static struct sk_buff *manage_oob(struct sk_buff *skb, struct sk_buff **last, WRITE_ONCE(u->oob_skb, NULL); if (!sock_flag(sk, SOCK_URGINLINE)) { + WRITE_ONCE(u->inq_len, u->inq_len - 1); __skb_unlink(skb, &sk->sk_receive_queue); unread_skb = skb; skb = skb_peek(&sk->sk_receive_queue); -- 2.55.0.1082.g2b9226bbc0-goog