From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59061) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1c8sLL-0008Bf-Dl for qemu-devel@nongnu.org; Mon, 21 Nov 2016 12:25:24 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1c8sLI-0006L0-5H for qemu-devel@nongnu.org; Mon, 21 Nov 2016 12:25:23 -0500 From: Thomas Huth Date: Mon, 21 Nov 2016 18:25:15 +0100 Message-Id: <1479749115-21932-1-git-send-email-thuth@redhat.com> Subject: [Qemu-devel] [PATCH] ui/vnc: Fix problem with sending too many bytes as server name List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org, Gerd Hoffmann Cc: qemu-stable@nongnu.org If the buffer is not big enough, snprintf() does not return the number of bytes that have been written to the buffer, but the number of bytes that would be needed for writing the whole string. By using this value for the following vnc_write() calls, we send some junk at the end of the name in case the qemu_name is longer than 1017 bytes, which could confuse the VNC clients. Fix this by adding an additional size check here. Buglink: https://bugs.launchpad.net/qemu/+bug/1637447 Signed-off-by: Thomas Huth --- ui/vnc.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/ui/vnc.c b/ui/vnc.c index 2c28a59..29aa9c4 100644 --- a/ui/vnc.c +++ b/ui/vnc.c @@ -2459,10 +2459,14 @@ static int protocol_client_init(VncState *vs, uint8_t *data, size_t len) pixel_format_message(vs); - if (qemu_name) + if (qemu_name) { size = snprintf(buf, sizeof(buf), "QEMU (%s)", qemu_name); - else + if (size > sizeof(buf)) { + size = sizeof(buf); + } + } else { size = snprintf(buf, sizeof(buf), "QEMU"); + } vnc_write_u32(vs, size); vnc_write(vs, buf, size); -- 1.8.3.1