[Spice-devel] [PATCH v2 1/2] covscan: initialize argv's copy

[Uri Lublin]

On 8/27/19 3:42 PM, Victor Toso wrote:
> From: Victor Toso <me at victortoso.com>
> 
> Otherwise we get a CLANG_WARNING due accessing garbage.
> 
> Covscan report:
>   > spice-vdagent-0.19.0/src/vdagent/vdagent.c:471:9: warning: 1st function call argument is an uninitialized value
>   > #        execvp(orig_argv[0], orig_argv);
>   > #        ^      ~~~~~~~~~~~~
>   > spice-vdagent-0.19.0/src/vdagent/vdagent.c:421:24: note: Storing uninitialized value
>   > #    char **orig_argv = g_memdup(argv, sizeof(char*) * (argc+1));
>   > #                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   > spice-vdagent-0.19.0/src/vdagent/vdagent.c:434:9: note: Assuming 'error' is equal to NULL
>   > #    if (error != NULL) {
>   > #        ^~~~~~~~~~~~~
>   > spice-vdagent-0.19.0/src/vdagent/vdagent.c:434:5: note: Taking false branch
>   > #    if (error != NULL) {
>   > #    ^
>   > spice-vdagent-0.19.0/src/vdagent/vdagent.c:442:9: note: Assuming 'portdev' is not equal to NULL
>   > #    if (portdev == NULL)
>   > #        ^~~~~~~~~~~~~~~
>   > spice-vdagent-0.19.0/src/vdagent/vdagent.c:442:5: note: Taking false branch
>   > #    if (portdev == NULL)
>   > #    ^
>   > spice-vdagent-0.19.0/src/vdagent/vdagent.c:445:9: note: Assuming 'vdagentd_socket' is not equal to NULL
>   > #    if (vdagentd_socket == NULL)
>   > #        ^~~~~~~~~~~~~~~~~~~~~~~
>   > spice-vdagent-0.19.0/src/vdagent/vdagent.c:445:5: note: Taking false branch
>   > #    if (vdagentd_socket == NULL)
>   > #    ^
>   > spice-vdagent-0.19.0/src/vdagent/vdagent.c:448:30: note: Assuming 'do_daemonize' is 0
>   > #    openlog("spice-vdagent", do_daemonize ? LOG_PID : (LOG_PID | LOG_PERROR),
>   > #                             ^~~~~~~~~~~~
>   > spice-vdagent-0.19.0/src/vdagent/vdagent.c:448:30: note: '?' condition is false
>   > spice-vdagent-0.19.0/src/vdagent/vdagent.c:451:9: note: Assuming the condition is false
>   > #    if (!g_file_test(portdev, G_FILE_TEST_EXISTS)) {
>   > #        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   > spice-vdagent-0.19.0/src/vdagent/vdagent.c:451:5: note: Taking false branch
>   > #    if (!g_file_test(portdev, G_FILE_TEST_EXISTS)) {
>   > #    ^
>   > spice-vdagent-0.19.0/src/vdagent/vdagent.c:457:9: note: Assuming 'do_daemonize' is 0
>   > #    if (do_daemonize)
>   > #        ^~~~~~~~~~~~
>   > spice-vdagent-0.19.0/src/vdagent/vdagent.c:457:5: note: Taking false branch
>   > #    if (do_daemonize)
>   > #    ^
>   > spice-vdagent-0.19.0/src/vdagent/vdagent.c:468:9: note: Assuming 'version_mismatch' is not equal to 0
>   > #    if (version_mismatch) {
>   > #        ^~~~~~~~~~~~~~~~
>   > spice-vdagent-0.19.0/src/vdagent/vdagent.c:468:5: note: Taking true branch
>   > #    if (version_mismatch) {
>   > #    ^
>   > spice-vdagent-0.19.0/src/vdagent/vdagent.c:471:9: note: 1st function call argument is an uninitialized value
>   > #        execvp(orig_argv[0], orig_argv);
>   > #        ^      ~~~~~~~~~~~~
>   > #  469|           syslog(LOG_INFO, "Version mismatch, restarting");
>   > #  470|           sleep(1);
>   > #  471|->         execvp(orig_argv[0], orig_argv);
>   > #  472|       }
>   > #  473|
> 
> Signed-off-by: Victor Toso <victortoso at redhat.com>
> ---
>   src/vdagent/vdagent.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/src/vdagent/vdagent.c b/src/vdagent/vdagent.c
> index 0e2e73e..5b146db 100644
> --- a/src/vdagent/vdagent.c
> +++ b/src/vdagent/vdagent.c
> @@ -418,7 +418,10 @@ int main(int argc, char *argv[])
>       GOptionContext *context;
>       GError *error = NULL;
>       VDAgent *agent;
> -    char **orig_argv = g_memdup(argv, sizeof(char*) * (argc+1));

I would not touch this line. It's already correct.
Just add the additional line.

> +    char **orig_argv;
> +
> +    orig_argv = g_memdup(argv, sizeof(char*) * (argc+1));
> +    orig_argv[argc] = NULL;

Please add a comment saying this line's only purpose is
to overcome a false-positive in clang.
For example (feel free to use a different one) something like:

+    /* This line is redundant. orig_argv[argc] is already NULL */
+    orig_argv[argc] = NULL; /* "fix" clang analyzer false-positive */

Uri

>   
>       context = g_option_context_new(NULL);
>       g_option_context_add_main_entries(context, entries, NULL);
>