[Spice-devel] [linux/vd_agent v1 1/2] covscan: check and initialize argv's copy

[Frediano Ziglio]

> 
> 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 | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/src/vdagent/vdagent.c b/src/vdagent/vdagent.c
> index 0e2e73e..982fc72 100644
> --- a/src/vdagent/vdagent.c
> +++ b/src/vdagent/vdagent.c
> @@ -418,7 +418,11 @@ int main(int argc, char *argv[])
>      GOptionContext *context;
>      GError *error = NULL;
>      VDAgent *agent;
> -    char **orig_argv = g_memdup(argv, sizeof(char*) * (argc+1));
> +    char **orig_argv;
> +
> +    g_return_val_if_fail(argc > 0 && argv != NULL, -1);
> +    orig_argv = g_memdup(argv, sizeof(char*) * (argc+1));
> +    orig_argv[argc] = NULL;
>  
>      context = g_option_context_new(NULL);
>      g_option_context_add_main_entries(context, entries, NULL);

I would say better to disable Clang test instead. The code is perfectly
fine. argc is at least 1 (the executable name!) and argv is always terminated
with NULL (that's the standard!).
See https://clang-analyzer.llvm.org/faq.html.

I don't know where this -1 come, but EXIT_FAILURE (which is usually 1) is the standard
return for main function.

Frediano