Am 27.05.19 um 10:17 schrieb Emil Velikov:
> 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
Well you could have saved your time, cause this is still a NAK.
For the record: I strongly think that we don't want to expose any render
functionality on the primary node.
To even go a step further I would say that at least on AMD hardware we
should completely disable DRI2 for one of the next generations.
As a follow up I would then completely disallow the DRM authentication
for amdgpu, so that the command submission interface on the primary node
can only be used by the display server.
Regards,
Christian.
>
> 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),
> };
>
> /**
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