From patchwork Tue Feb 13 08:54:07 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: "Vladislav Valtchev (VMware)" X-Patchwork-Id: 10758543 Return-Path: linux-trace-devel-owner@vger.kernel.org Received: from mail-wr0-f194.google.com ([209.85.128.194]:39175 "EHLO mail-wr0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933741AbeBMIyD (ORCPT ); Tue, 13 Feb 2018 03:54:03 -0500 Received: by mail-wr0-f194.google.com with SMTP id w77so3319602wrc.6 for ; Tue, 13 Feb 2018 00:54:02 -0800 (PST) From: "Vladislav Valtchev (VMware)" To: rostedt@goodmis.org Cc: linux-trace-devel@vger.kernel.org, "Vladislav Valtchev (VMware)" Subject: [PATCH] trace-cmd: virt-server: fix snprintf-related warnings Date: Tue, 13 Feb 2018 10:54:07 +0200 Message-Id: <20180213085407.10660-1-vladislav.valtchev@gmail.com> MIME-Version: 1.0 Sender: linux-trace-devel-owner@vger.kernel.org List-ID: Content-Length: 2460 Currently the build of trace-cmd in the virt-server branch produces warnings like: - format not a string literal and no format arguments [-Wformat-security] - ‘%s’ directive output may be truncated writing up to 255 bytes into a region of size 233 [-Wformat-truncation=] Compiler's concerns are reasonable. In particular, the statement at trace-listen.c:1468: snprintf(un_server->sun_path, strlen(file)+1, file); Contains two bugs: - it is dangerous to use a string instead of a format string - the 2nd argument should be buffer's size, not the size of the source string. The first kind of warnings (2 cases) have been fixed by using strncpy() instead of snprintf() [+ the right buffer size]. The second kind of warnings (1 case) instead, appears because of the statement: [trace-listen.c:954] snprintf(file_name, NAME_MAX, LIBVIRT_DOMAIN_PATH"%s", dirent->d_name); And has been fixed by using a pair of strcpy() + strncat() with the 'size' argument of strncat() being: sizeof(file_name) - strlen(LIBVIRT_DOMAIN_PATH) - 1 NOTE: sizeof(file_name) == NAME_MAX. Signed-off-by: Vladislav Valtchev (VMware) --- trace-listen.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/trace-listen.c b/trace-listen.c index afe6084..744c6fb 100644 --- a/trace-listen.c +++ b/trace-listen.c @@ -954,8 +954,12 @@ static char *get_guest_domain_from_pid_libvirt(int pid) } for (dirent = readdir(dir); dirent != NULL; dirent = readdir(dir)) { - snprintf(file_name, NAME_MAX, LIBVIRT_DOMAIN_PATH"%s", - dirent->d_name); + + strcpy(file_name, LIBVIRT_DOMAIN_PATH); + strncat(file_name, + dirent->d_name, + sizeof(file_name) - strlen(LIBVIRT_DOMAIN_PATH) - 1); + file_name_ret = strstr(file_name, ".pid"); if (file_name_ret) { fd = open(file_name, O_RDONLY); @@ -1468,7 +1472,7 @@ static int create_socket(struct sockaddr_un *un_server, return sfd; un_server->sun_family = AF_UNIX; - snprintf(un_server->sun_path, strlen(file)+1, file); + strncpy(un_server->sun_path, file, sizeof(un_server->sun_path) - 1); return sfd; } @@ -2301,7 +2305,7 @@ static int set_up_socket(const char *file) pdie("socket"); un_server.sun_family = AF_UNIX; - snprintf(un_server.sun_path, PATH_MAX, file); + strncpy(un_server.sun_path, file, sizeof(un_server.sun_path) - 1); if (bind(sfd, (struct sockaddr *)&un_server, slen) < 0) pdie("bind");