From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48990) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ctwlT-0002q4-Pt for qemu-devel@nongnu.org; Fri, 31 Mar 2017 09:38:56 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ctwlS-00027p-U7 for qemu-devel@nongnu.org; Fri, 31 Mar 2017 09:38:55 -0400 From: Peter Maydell Date: Fri, 31 Mar 2017 14:38:49 +0100 Message-Id: <1490967529-4767-1-git-send-email-peter.maydell@linaro.org> Subject: [Qemu-devel] [PATCH] qemu-io-cmds: Assert that global and nofile commands don't use ct->perms List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: patches@linaro.org, Kevin Wolf , Max Reitz , qemu-block@nongnu.org It would be a bug for a command with the CMD_NOFILE_OK or CMD_FLAG_GLOBAL flags set to also set the ct->perms field, because the former says "OK for a file not to be open" but the latter is a check on a file. Add an assertion in qemuio_add_command() so we can catch that sort of buggy command definition immediately rather than it being a bug that only manifests when a particular set of command line options is used. (Coverity gets confused about this (CID 1371723) and reports that we might dereference a NULL blk pointer in this case, because it can't tell that that code path never happens with the cmdinfo_t that we have. This commit won't help unconfuse it, but it does fix the underlying issue.) Signed-off-by: Peter Maydell --- We could also try to add some kind of assert in command() to persuade coverity that it can't get there with a NULL block and ct->perms non-zero, but I think I'd rather just mark the issue as a false-positive and move on. qemu-io-cmds.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c index 2c48f9c..883f53b 100644 --- a/qemu-io-cmds.c +++ b/qemu-io-cmds.c @@ -35,6 +35,13 @@ static int compare_cmdname(const void *a, const void *b) void qemuio_add_command(const cmdinfo_t *ci) { + /* ci->perm assumes a file is open, but the GLOBAL and NOFILE_OK + * flags allow it not to be, so that combination is invalid. + * Catch it now rather than letting it manifest as a crash if a + * particular set of command line options are used. + */ + assert(ci->perm == 0 || + (ci->flags & (CMD_FLAG_GLOBAL | CMD_NOFILE_OK)) == 0); cmdtab = g_renew(cmdinfo_t, cmdtab, ++ncmds); cmdtab[ncmds - 1] = *ci; qsort(cmdtab, ncmds, sizeof(*cmdtab), compare_cmdname); -- 2.7.4