| Message ID | 1490967529-4767-1-git-send-email-peter.maydell@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
On 31.03.2017 15:38, Peter Maydell wrote: > 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 <peter.maydell@linaro.org> > --- > 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. I think having the assertion in qemuio_add_command() is nicer because if we break it we will definitely notice just by launching qemu-io. > qemu-io-cmds.c | 7 +++++++ > 1 file changed, 7 insertions(+) Thanks, applied to my block branch: https://github.com/XanClic/qemu/commits/block Max
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);
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 <peter.maydell@linaro.org> --- 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(+) -- 2.7.4