[PATCH 12/33] drm/i915/gem: Disallow creating contexts with too many engines

[Jason Ekstrand]

There's no sense in allowing userspace to create more engines than it
can possibly access via execbuf.

Signed-off-by: Jason Ekstrand <jason at jlekstrand.net>
Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
---
 drivers/gpu/drm/i915/gem/i915_gem_context.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
index 5e159fb526631..2b9207b557cc9 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -1639,11 +1639,11 @@ set_engines(struct i915_gem_context *ctx,
 		return -EINVAL;
 	}
 
-	/*
-	 * Note that I915_EXEC_RING_MASK limits execbuf to only using the
-	 * first 64 engines defined here.
-	 */
 	num_engines = (args->size - sizeof(*user)) / sizeof(*user->engines);
+	/* RING_MASK has no shift so we can use it directly here */
+	if (num_engines > I915_EXEC_RING_MASK + 1)
+		return -EINVAL;
+
 	set.engines = alloc_engines(num_engines);
 	if (!set.engines)
 		return -ENOMEM;
-- 
2.31.1