Re: [PATCH 1/2] drm/i915: Reject unknown syncobj flags

[Chris Wilson]

Quoting Tvrtko Ursulin (2017-10-31 10:23:25)
> From: Tvrtko Ursulin 
> 
> We have to reject unknown flags for uAPI considerations, and also
> because the curent implementation limits their i915 storage space
> to two bits.
> 
> v2: (Chris Wilson)
>  * Fix fail in ABI check.
>  * Added unknown flags and BUILD_BUG_ON.
> 
> v3:
>  * Use ARCH_KMALLOC_MINALIGN instead of alignof. (Chris Wilson)
> 
> Signed-off-by: Tvrtko Ursulin 
> Fixes: cf6e7bac6357 ("drm/i915: Add support for drm syncobjs")
> Cc: Jason Ekstrand 
> Cc: Chris Wilson 
> Cc: Jani Nikula 
> Cc: Joonas Lahtinen 
> Cc: Rodrigo Vivi 
> Cc: David Airlie 
> Cc: intel-...@lists.freedesktop.org
> Cc: dri-devel@lists.freedesktop.org
> ---
>  drivers/gpu/drm/i915/i915_gem_execbuffer.c | 8 
>  include/uapi/drm/i915_drm.h| 1 +
>  2 files changed, 9 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c 
> b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> index 3d7190764f10..a53be7d01055 100644
> --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> @@ -2100,6 +2100,11 @@ get_fence_array(struct drm_i915_gem_execbuffer2 *args,
> goto err;
> }
>  
> +   if (fence.flags & __I915_EXEC_FENCE_UNKNOWN_FLAGS) {
> +   err = -EINVAL;
> +   goto err;
> +   }
> +
> syncobj = drm_syncobj_find(file, fence.handle);
> if (!syncobj) {
> DRM_DEBUG("Invalid syncobj handle provided\n");
> @@ -2107,6 +2112,9 @@ get_fence_array(struct drm_i915_gem_execbuffer2 *args,
> goto err;
> }
>  
> +   BUILD_BUG_ON(~(ARCH_KMALLOC_MINALIGN - 1) &
> +~__I915_EXEC_FENCE_UNKNOWN_FLAGS);
> +
> fences[n] = ptr_pack_bits(syncobj, fence.flags, 2);

Was pondering how to tie the .n=2 into the BUILD_BUG_ON, but that
doesn't limit the improvement and fixes in this patch, so

Reviewed-by: Chris Wilson 
-Chris
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[PATCH 1/2] drm/i915: Reject unknown syncobj flags

[Tvrtko Ursulin]

From: Tvrtko Ursulin 

We have to reject unknown flags for uAPI considerations, and also
because the curent implementation limits their i915 storage space
to two bits.

v2: (Chris Wilson)
 * Fix fail in ABI check.
 * Added unknown flags and BUILD_BUG_ON.

v3:
 * Use ARCH_KMALLOC_MINALIGN instead of alignof. (Chris Wilson)

Signed-off-by: Tvrtko Ursulin 
Fixes: cf6e7bac6357 ("drm/i915: Add support for drm syncobjs")
Cc: Jason Ekstrand 
Cc: Chris Wilson 
Cc: Jani Nikula 
Cc: Joonas Lahtinen 
Cc: Rodrigo Vivi 
Cc: David Airlie 
Cc: intel-...@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
---
 drivers/gpu/drm/i915/i915_gem_execbuffer.c | 8 
 include/uapi/drm/i915_drm.h| 1 +
 2 files changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c 
b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 3d7190764f10..a53be7d01055 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -2100,6 +2100,11 @@ get_fence_array(struct drm_i915_gem_execbuffer2 *args,
goto err;
}
 
+   if (fence.flags & __I915_EXEC_FENCE_UNKNOWN_FLAGS) {
+   err = -EINVAL;
+   goto err;
+   }
+
syncobj = drm_syncobj_find(file, fence.handle);
if (!syncobj) {
DRM_DEBUG("Invalid syncobj handle provided\n");
@@ -2107,6 +2112,9 @@ get_fence_array(struct drm_i915_gem_execbuffer2 *args,
goto err;
}
 
+   BUILD_BUG_ON(~(ARCH_KMALLOC_MINALIGN - 1) &
+~__I915_EXEC_FENCE_UNKNOWN_FLAGS);
+
fences[n] = ptr_pack_bits(syncobj, fence.flags, 2);
}
 
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index 125bde7d9504..ac3c6503ca27 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -839,6 +839,7 @@ struct drm_i915_gem_exec_fence {
 
 #define I915_EXEC_FENCE_WAIT(1<<0)
 #define I915_EXEC_FENCE_SIGNAL  (1<<1)
+#define __I915_EXEC_FENCE_UNKNOWN_FLAGS (-(I915_EXEC_FENCE_SIGNAL << 1))
__u32 flags;
 };
 
-- 
2.9.5

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