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[87.12.139.105]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4887a630922sm244763235e9.0.2026.04.02.06.28.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Apr 2026 06:28:36 -0700 (PDT) Date: Thu, 2 Apr 2026 15:28:25 +0200 From: Stefano Garzarella To: Luigi Leonardi Cc: Stefan Hajnoczi , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , Eugenio =?utf-8?B?UMOpcmV6?= , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Arseniy Krasnov , kvm@vger.kernel.org, virtualization@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net 2/2] vsock/test: add MSG_PEEK after partial recv test Message-ID: References: <20260402-fix_peek-v1-0-ad274fcef77b@redhat.com> <20260402-fix_peek-v1-2-ad274fcef77b@redhat.com> 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=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20260402-fix_peek-v1-2-ad274fcef77b@redhat.com> On Thu, Apr 02, 2026 at 10:18:02AM +0200, Luigi Leonardi wrote: >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_peek()` WARNING: Prefer a maximum 75 chars per line (possible unwrapped commit description?) #11: This is to test a bug that was present in the `virtio_transport_stream_do_peek()` >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_test.c >index 5bd20ccd9335caafe68e8b7a5d02a4deb3d2deec..308f9f8f30d22bec5aaa282356e400d8438fe321 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 test_opts *opts) > return test_msg_peek_server(opts, false); > } > >+#define PEEK_AFTER_RECV_LEN 100 Why 100 ? Better to use a power of 2 IMO like we do in all other cases IIRC. >+ >+static void test_stream_peek_after_recv_client(const struct test_opts *opts) >+{ >+ unsigned char buf[PEEK_AFTER_RECV_LEN]; >+ int fd; >+ int i; nit: int fd, i; >+ >+ fd = vsock_stream_connect(opts->peer_cid, opts->peer_port); >+ if (fd < 0) { >+ perror("connect"); >+ exit(EXIT_FAILURE); >+ } >+ >+ for (i = 0; i < sizeof(buf); i++) >+ buf[i] = (unsigned char)i; Why setting the payload in this way ? Can we just do a memset() ? >+ >+ control_expectln("SRVREADY"); Why we need this barrier ? >+ >+ send_buf(fd, buf, sizeof(buf), 0, sizeof(buf)); >+ >+ close(fd); >+} >+ >+static void test_stream_peek_after_recv_server(const struct test_opts *opts) >+{ >+ unsigned char buf[PEEK_AFTER_RECV_LEN]; >+ int half = PEEK_AFTER_RECV_LEN / 2; >+ ssize_t ret; >+ int fd; >+ >+ fd = 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); Why reading half of the size ? IMO is better to read just 1 byte, since it is almost certain that an skb does not have a 1-byte payload. >+ >+ /* Try to peek more than what remains: should return only 'half' How we are sure that the sender sent all the bytes ? >+ * bytes. Note: we can't use recv_buf() because it loops until >+ * all requested bytes are returned. Why this is a problem ? (an useful comment should explain the reason) >+ */ >+ ret = recv(fd, buf, sizeof(buf), MSG_PEEK); >+ if (ret < 0) { Should we handle EINTR like we do in recv_buf() ? But I still don't understand why we can't use it directly. Thanks, Stefano >+ perror("recv"); >+ exit(EXIT_FAILURE); >+ } else if (ret != 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[] = { > .run_client = test_stream_tx_credit_bounds_client, > .run_server = test_stream_tx_credit_bounds_server, > }, >+ { >+ .name = "SOCK_STREAM MSG_PEEK after partial recv", >+ .run_client = test_stream_peek_after_recv_client, >+ .run_server = test_stream_peek_after_recv_server, >+ }, > {}, > }; > > >-- >2.53.0 >