Fix pointer accessing local variable out of scope

The C11 standard states that the value of a pointer is undefined
outside of its lifetime. Since we were initilizing the argv pointer
in two conditional blocks, compilers that implement this standard were
cleaning up the value and this caused invalid dereferences of the
pointer.

The change introduces two local variables with the same lifetime of the
argv pointer and assigns these in the conditional blocks instead.

Signed-off-by: Evan Lezar <[email protected]>

Author: elezar

src/nvc_ldcache.c

@@ -472,18 +472,30 @@ nvc_ldcache_update(struct nvc_context *ctx, const struct nvc_container *cnt)
         if (validate_args(ctx, cnt != NULL) < 0)
                 return (-1);
 
+        /*
+         * The C11 standard states that the value of a pointer is undefined
+         * outside of its lifetime. Since we were initilizing the argv pointer
+         * in two conditional blocks below, compilers that implement this
+         * standard clean up the local value and this causes invalid
+         * dereferences of the pointer when it is used later.
+         *
+         * See https://github.com/NVIDIA/libnvidia-container/issues/316 for an
+         * in-depth investigation.
+         */
+        char *argv_default[] = {cnt->cfg.ldconfig, "-f", "/etc/ld.so.conf", "-C", "/etc/ld.so.cache", cnt->cfg.libs_dir, cnt->cfg.libs32_dir, NULL};
+        char *argv_with_compat_dir[] = {cnt->cfg.ldconfig, "-f", "/etc/ld.so.conf", "-C", "/etc/ld.so.cache", cnt->cuda_compat_dir, cnt->cfg.libs_dir, cnt->cfg.libs32_dir, NULL};
         if ((cnt->flags & OPT_CUDA_COMPAT_MODE_LDCONFIG) && (cnt->cuda_compat_dir != NULL)) {
                 /*
                  * We include the cuda_compat_dir directory on the ldconfig
                  * command line. This ensures that the CUDA Forward compat
                  * libraries take precendence over the user-mode driver
                  * libraries in the standard library paths (libs_dir and
                  * libs32_dir).
-                 * */
+                 */
                 log_info("prefering CUDA Forward Compatibility dir when running ldconfig");
-                argv = (char * []){cnt->cfg.ldconfig, "-f", "/etc/ld.so.conf", "-C", "/etc/ld.so.cache", cnt->cuda_compat_dir, cnt->cfg.libs_dir, cnt->cfg.libs32_dir, NULL};
+                argv = argv_with_compat_dir;
         } else {
-                argv = (char * []){cnt->cfg.ldconfig, "-f", "/etc/ld.so.conf", "-C", "/etc/ld.so.cache", cnt->cfg.libs_dir, cnt->cfg.libs32_dir, NULL};
+                argv = argv_default;
         }
 
         if (*argv[0] == '@') {