zink: Return early if the file descriptor could not have been duplicated/acquired

Do not continue and call drmIoctl on an invalid file descriptor.

Fix defect reported by Coverity Scan.

Argument cannot be negative

The negative argument will be interpreted as a very large unsigned value.

CID: 1544377
Cc: mesa-stable
Signed-off-by: Corentin Noël <[email protected]>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27788>
(cherry picked from commit b6962bb)

Author: tintou

.pick_status.json

@@ -1444,7 +1444,7 @@
         "description": "zink: Return early if the file descriptor could not have been duplicated/acquired",
         "nominated": true,
         "nomination_type": 0,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": null,
         "notes": null

src/gallium/drivers/zink/zink_screen.c

@@ -2277,7 +2277,7 @@ zink_screen_export_dmabuf_semaphore(struct zink_screen *screen, struct zink_reso
       .fd = -1,
    };
 
-   int fd;
+   int fd = -1;
    if (res->obj->is_aux) {
       fd = os_dupfd_cloexec(res->obj->handle);
    } else {
@@ -2288,6 +2288,11 @@ zink_screen_export_dmabuf_semaphore(struct zink_screen *screen, struct zink_reso
       VKSCR(GetMemoryFdKHR)(screen->dev, &fd_info, &fd);
    }
 
+   if (unlikely(fd < 0)) {
+      mesa_loge("MESA: Unable to get a valid memory fd");
+      return VK_NULL_HANDLE;
+   }
+
    int ret = drmIoctl(fd, DMA_BUF_IOCTL_EXPORT_SYNC_FILE, &export);
    if (ret) {
       if (errno == ENOTTY || errno == EBADF || errno == ENOSYS) {