From: Emil Velikov <emil.velikov@xxxxxxxxxxxxx>
Currently one can circumvent DRM_AUTH, when the ioctl is exposed via the
render node. A seemingly deliberate design decision.
Hence we can drop the DRM_AUTH all together (details in follow-up patch)
yet not all userspace checks if it's authenticated, but instead uses
uncommon assumptions.
After days of digging through git log and testing, only a single (ab)use
was spotted - the Mesa RADV driver, using the AMDGPU_INFO ioctl and
assuming that failure implies lack of authentication.
Affected versions are:
- the whole 18.2.x series, which is EOL
- the whole 18.3.x series, which is EOL
- the 19.0.x series, prior to 19.0.4
Add a special quirk for that case, thus we can drop DRM_AUTH bits as
mentioned earlier.
Since all the affected userspace is EOL, we also add a kconfig option
to disable this quirk.
The whole approach is inspired by DRIVER_KMS_LEGACY_CONTEXT
Cc: Alex Deucher <alexander.deucher@xxxxxxx>
Cc: Christian König <christian.koenig@xxxxxxx>
Cc: amd-gfx@xxxxxxxxxxxxxxxxxxxxx
Cc: David Airlie <airlied@xxxxxxxx>
Cc: Daniel Vetter <daniel@xxxxxxxx>
Signed-off-by: Emil Velikov <emil.velikov@xxxxxxxxxxxxx>
---
drivers/gpu/drm/amd/amdgpu/Kconfig | 16 ++++++++++++++++
drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c | 12 +++++++++++-
drivers/gpu/drm/drm_ioctl.c | 5 +++++
include/drm/drm_ioctl.h | 17 +++++++++++++++++
4 files changed, 49 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/Kconfig b/drivers/gpu/drm/amd/amdgpu/Kconfig
index 9221e5489069..da415f445187 100644
--- a/drivers/gpu/drm/amd/amdgpu/Kconfig
+++ b/drivers/gpu/drm/amd/amdgpu/Kconfig
@@ -40,6 +40,22 @@ config DRM_AMDGPU_GART_DEBUGFS
Selecting this option creates a debugfs file to inspect the mapped
pages. Uses more memory for housekeeping, enable only for debugging.
+config DRM_AMDGPU_FORCE_AUTH
+ bool "Force authentication check on AMDGPU_INFO ioctl"
+ default y
+ help
+ There were some version of the Mesa RADV drivers, which relied on
+ the ioctl failing, if the client is not authenticated.
+
+ Namely, the following versions are affected:
+ - the whole 18.2.x series, which is EOL
+ - the whole 18.3.x series, which is EOL
+ - the 19.0.x series, prior to 19.0.4
+
+ Modern distributions, should disable this. That will allow various
+ other clients to work, that would otherwise require root privileges.
+
+
source "drivers/gpu/drm/amd/acp/Kconfig"
source "drivers/gpu/drm/amd/display/Kconfig"
source "drivers/gpu/drm/amd/amdkfd/Kconfig"
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
index b17d0545728e..b8076929440b 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
@@ -1214,7 +1214,17 @@ const struct drm_ioctl_desc amdgpu_ioctls_kms[] = {
DRM_IOCTL_DEF_DRV(AMDGPU_GEM_MMAP, amdgpu_gem_mmap_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),
DRM_IOCTL_DEF_DRV(AMDGPU_GEM_WAIT_IDLE, amdgpu_gem_wait_idle_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),
DRM_IOCTL_DEF_DRV(AMDGPU_CS, amdgpu_cs_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),
- DRM_IOCTL_DEF_DRV(AMDGPU_INFO, amdgpu_info_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),
+ /* The DRM_FORCE_AUTH is effectively a workaround for the RADV Mesa driver.
+ * This is required for Mesa:
+ * - the whole 18.2.x series, which is EOL
+ * - the whole 18.3.x series, which is EOL
+ * - the 19.0.x series, prior to 19.0.4
+ */
+ DRM_IOCTL_DEF_DRV(AMDGPU_INFO, amdgpu_info_ioctl,
+#if defined(DRM_AMDGPU_FORCE_AUTH)
+ DRM_FORCE_AUTH|
+#endif
+ DRM_AUTH|DRM_RENDER_ALLOW),
DRM_IOCTL_DEF_DRV(AMDGPU_WAIT_CS, amdgpu_cs_wait_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),
DRM_IOCTL_DEF_DRV(AMDGPU_WAIT_FENCES, amdgpu_cs_wait_fences_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),
DRM_IOCTL_DEF_DRV(AMDGPU_GEM_METADATA, amdgpu_gem_metadata_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),
diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index 2263e3ddd822..9841c0076f02 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -544,6 +544,11 @@ int drm_ioctl_permit(u32 flags, struct drm_file *file_priv)
drm_is_render_client(file_priv)))
return -EACCES;
+ /* FORCE_AUTH is only for authenticated or render client */
+ if (unlikely((flags & DRM_FORCE_AUTH) && !drm_is_render_client(file_priv) &&
+ !file_priv->authenticated))
+ return -EACCES;
+
return 0;
}
EXPORT_SYMBOL(drm_ioctl_permit);
diff --git a/include/drm/drm_ioctl.h b/include/drm/drm_ioctl.h
index fafb6f592c4b..6084ee32043d 100644
--- a/include/drm/drm_ioctl.h
+++ b/include/drm/drm_ioctl.h
@@ -126,6 +126,23 @@ enum drm_ioctl_flags {
* not set DRM_AUTH because they do not require authentication.
*/
DRM_RENDER_ALLOW = BIT(5),
+ /**
+ * @DRM_FORCE_AUTH:
+ *
+ * Authentication of the primary node is mandatory. Regardless that the
+ * user can usually circumvent that by using the render node with exact
+ * same ioctl.
+ *
+ * Note: this is effectively a workaround for AMDGPU AMDGPU_INFO ioctl
+ * and the RADV Mesa driver. This is required for Mesa:
+ * - the whole 18.2.x series, which is EOL
+ * - the whole 18.3.x series, which is EOL
+ * - the 19.0.x series, prior to 19.0.4
+ *
+ * Note: later patch will effectively drop the DRM_AUTH for ioctls
+ * annotated as DRM_AUTH | DRM_RENDER_ALLOW.
+ */
+ DRM_FORCE_AUTH = BIT(6),
};
/**
--
2.21.0
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