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Thu, 02 Apr 2026 01:18:05 -0700 (PDT) Received: from lleonard-thinkpadx1carbongen13.rmtit.csb ([176.206.19.176]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4887e735532sm214476005e9.0.2026.04.02.01.18.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Apr 2026 01:18:04 -0700 (PDT) From: Luigi Leonardi Date: Thu, 02 Apr 2026 10:18:01 +0200 Subject: [PATCH net 1/2] vsock/virtio: fix MSG_PEEK ignoring skb offset when calculating bytes to copy Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260402-fix_peek-v1-1-ad274fcef77b@redhat.com> References: <20260402-fix_peek-v1-0-ad274fcef77b@redhat.com> In-Reply-To: <20260402-fix_peek-v1-0-ad274fcef77b@redhat.com> To: Stefan Hajnoczi , Stefano Garzarella , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , =?utf-8?q?Eugenio_P=C3=A9rez?= , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Arseniy Krasnov Cc: kvm@vger.kernel.org, virtualization@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Luigi Leonardi X-Mailer: b4 0.14.2 `virtio_transport_stream_do_peek()` does not account for the skb offset when computing the number of bytes to copy. This means that, after a partial recv() that advances the offset, a peek requesting more bytes than are available in the sk_buff causes `skb_copy_datagram_iter()` to go past the valid payload, resulting in a -EF= AULT. The dequeue path already handles this correctly. Apply the same logic to the peek path. Fixes: 0df7cd3c13e4 ("vsock/virtio/vhost: read data from non-linear skb") Signed-off-by: Luigi Leonardi Acked-by: Arseniy Krasnov Reviewed-by: Stefano Garzarella --- net/vmw_vsock/virtio_transport_common.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio= _transport_common.c index 8a9fb23c6e853dfea0a24d3787f7d6eb351dd6c6..4b65bfe5d875111f115e0fc4c67= 27adb66f34830 100644 --- a/net/vmw_vsock/virtio_transport_common.c +++ b/net/vmw_vsock/virtio_transport_common.c @@ -547,9 +547,8 @@ virtio_transport_stream_do_peek(struct vsock_sock *vsk, skb_queue_walk(&vvs->rx_queue, skb) { size_t bytes; =20 - bytes =3D len - total; - if (bytes > skb->len) - bytes =3D skb->len; + bytes =3D min_t(size_t, len - total, + skb->len - VIRTIO_VSOCK_SKB_CB(skb)->offset); =20 spin_unlock_bh(&vvs->rx_lock); =20 --=20 2.53.0 From nobody Sun Jun 14 09:58:36 2026 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id ECB7B3A0E8A for ; 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Thu, 02 Apr 2026 01:18:07 -0700 (PDT) X-Received: by 2002:a05:600c:8184:b0:483:9139:4c1d with SMTP id 5b1f17b1804b1-48883590456mr113865405e9.14.1775117887065; Thu, 02 Apr 2026 01:18:07 -0700 (PDT) Received: from lleonard-thinkpadx1carbongen13.rmtit.csb ([176.206.19.176]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4887e735532sm214476005e9.0.2026.04.02.01.18.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Apr 2026 01:18:06 -0700 (PDT) From: Luigi Leonardi Date: Thu, 02 Apr 2026 10:18:02 +0200 Subject: [PATCH net 2/2] vsock/test: add MSG_PEEK after partial recv test Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260402-fix_peek-v1-2-ad274fcef77b@redhat.com> References: <20260402-fix_peek-v1-0-ad274fcef77b@redhat.com> In-Reply-To: <20260402-fix_peek-v1-0-ad274fcef77b@redhat.com> To: Stefan Hajnoczi , Stefano Garzarella , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , =?utf-8?q?Eugenio_P=C3=A9rez?= , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Arseniy Krasnov Cc: kvm@vger.kernel.org, virtualization@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Luigi Leonardi X-Mailer: b4 0.14.2 Add a test that verifies MSG_PEEK works correctly after a partial recv(). This is to test a bug that was present in the `virtio_transport_stream_do_p= eek()` when computing the number of bytes to copy: After a partial read, the peek function didn't take into consideration the number of bytes that were already read. So peeking the whole buffer would cause a out-of-bounds = read, that resulted in a -EFAULT. This test does exactly this: do a partial recv on a buffer, then try to peek the whole buffer content. Signed-off-by: Luigi Leonardi --- tools/testing/vsock/vsock_test.c | 64 ++++++++++++++++++++++++++++++++++++= ++++ 1 file changed, 64 insertions(+) diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_t= est.c index 5bd20ccd9335caafe68e8b7a5d02a4deb3d2deec..308f9f8f30d22bec5aaa282356e= 400d8438fe321 100644 --- a/tools/testing/vsock/vsock_test.c +++ b/tools/testing/vsock/vsock_test.c @@ -346,6 +346,65 @@ static void test_stream_msg_peek_server(const struct t= est_opts *opts) return test_msg_peek_server(opts, false); } =20 +#define PEEK_AFTER_RECV_LEN 100 + +static void test_stream_peek_after_recv_client(const struct test_opts *opt= s) +{ + unsigned char buf[PEEK_AFTER_RECV_LEN]; + int fd; + int i; + + fd =3D vsock_stream_connect(opts->peer_cid, opts->peer_port); + if (fd < 0) { + perror("connect"); + exit(EXIT_FAILURE); + } + + for (i =3D 0; i < sizeof(buf); i++) + buf[i] =3D (unsigned char)i; + + control_expectln("SRVREADY"); + + send_buf(fd, buf, sizeof(buf), 0, sizeof(buf)); + + close(fd); +} + +static void test_stream_peek_after_recv_server(const struct test_opts *opt= s) +{ + unsigned char buf[PEEK_AFTER_RECV_LEN]; + int half =3D PEEK_AFTER_RECV_LEN / 2; + ssize_t ret; + int fd; + + fd =3D vsock_stream_accept(VMADDR_CID_ANY, opts->peer_port, NULL); + if (fd < 0) { + perror("accept"); + exit(EXIT_FAILURE); + } + + control_writeln("SRVREADY"); + + /* Partial recv to advance offset within the skb */ + recv_buf(fd, buf, half, 0, half); + + /* Try to peek more than what remains: should return only 'half' + * bytes. Note: we can't use recv_buf() because it loops until + * all requested bytes are returned. + */ + ret =3D recv(fd, buf, sizeof(buf), MSG_PEEK); + if (ret < 0) { + perror("recv"); + exit(EXIT_FAILURE); + } else if (ret !=3D half) { + fprintf(stderr, "MSG_PEEK after partial recv returned %d (expected %d)\n= ", + ret, half); + exit(EXIT_FAILURE); + } + + close(fd); +} + #define SOCK_BUF_SIZE (2 * 1024 * 1024) #define SOCK_BUF_SIZE_SMALL (64 * 1024) #define MAX_MSG_PAGES 4 @@ -2520,6 +2579,11 @@ static struct test_case test_cases[] =3D { .run_client =3D test_stream_tx_credit_bounds_client, .run_server =3D test_stream_tx_credit_bounds_server, }, + { + .name =3D "SOCK_STREAM MSG_PEEK after partial recv", + .run_client =3D test_stream_peek_after_recv_client, + .run_server =3D test_stream_peek_after_recv_server, + }, {}, }; =20 --=20 2.53.0