From 8f30e90fc104c2b9e044d279fe953a308c44353f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Michel=20D=C3=A4nzer?= <mdaenzer@redhat.com>
Date: Thu, 19 Mar 2026 18:31:32 +0100
Subject: [PATCH] winsys/amdgpu: Prefer render node FD for
 ac_drm_device_initialize

If the FD passed in isn't from a render node, try to determine the
corresponding render node and open it. If that succeeds, pass the
render node FD to ac_drm_device_initialize.

The existing code already detects when ac_drm_device_get_fd doesn't
return the FD passed in, and handles that case correctly.

This avoids issues with unauthenticated FDs from card nodes.

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/7289

v2:
* Always close render_fd after calling ac_drm_device_initialize for it.
  (Pierre-Eric Pelloux-Prayer)
* Formatting tweaks for logging when ac_drm_device_initialize fails for
  render_fd.
v3: (Pierre-Eric Pelloux-Prayer)
* Log render_device path when ac_drm_device_initialize fails for
  render_fd.
* Fix render_device string leak.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/40519>
---
 src/gallium/winsys/amdgpu/drm/amdgpu_winsys.c | 31 ++++++++++++++++---
 1 file changed, 26 insertions(+), 5 deletions(-)

diff --git a/src/gallium/winsys/amdgpu/drm/amdgpu_winsys.c b/src/gallium/winsys/amdgpu/drm/amdgpu_winsys.c
index ada39e7f278..223c86473fa 100644
--- a/src/gallium/winsys/amdgpu/drm/amdgpu_winsys.c
+++ b/src/gallium/winsys/amdgpu/drm/amdgpu_winsys.c
@@ -397,7 +397,7 @@ amdgpu_winsys_create(int fd, const struct pipe_screen_config *config,
 {
    struct amdgpu_screen_winsys *sws;
    struct amdgpu_winsys *aws;
-   ac_drm_device *dev;
+   ac_drm_device *dev = NULL;
    uint32_t drm_major, drm_minor;
    int r;
 
@@ -415,10 +415,31 @@ amdgpu_winsys_create(int fd, const struct pipe_screen_config *config,
 
    /* Initialize the amdgpu device. This should always return the same pointer
     * for the same fd. */
-   r = ac_drm_device_initialize(fd, is_virtio, &drm_major, &drm_minor, &dev);
-   if (r) {
-      mesa_loge("amdgpu: amd%s_device_initialize failed.\n", is_virtio ? "vgpu" : "gpu");
-      goto fail;
+   if (drmGetNodeTypeFromFd(fd) != DRM_NODE_RENDER) {
+      char *render_device = drmGetRenderDeviceNameFromFd(fd);
+
+      if (render_device) {
+         int render_fd = open(render_device, O_RDWR | O_CLOEXEC);
+
+         if (render_fd >= 0) {
+            r = ac_drm_device_initialize(render_fd, is_virtio, &drm_major, &drm_minor, &dev);
+            close(render_fd);
+            if (r) {
+               mesa_logd("amdgpu: amd%s_device_initialize failed for %s\n",
+                         is_virtio ? "vgpu" : "gpu", render_device);
+            }
+         }
+
+         free(render_device);
+      }
+   }
+
+   if (!dev) {
+      r = ac_drm_device_initialize(fd, is_virtio, &drm_major, &drm_minor, &dev);
+      if (r) {
+         mesa_loge("amdgpu: amd%s_device_initialize failed.\n", is_virtio ? "vgpu" : "gpu");
+         goto fail;
+      }
    }
 
    /* Lookup a winsys if we have already created one for this device. */