drm/radeon: prevent crash in the ring space allocation

If the requested number of DWs on the ring is larger than
the size of the ring itself, return an error.

In testing with large VM updates, we've seen crashes when we
try and allocate more space on the ring than the total size
of the ring without checking.

This prevents the crash but for large VM updates or bo moves
of very large buffers, we will need to break the transaction
down into multiple batches.  I have patches to use IBs for
the next kernel.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

diff --git a/drivers/gpu/drm/radeon/radeon_ring.c b/drivers/gpu/drm/radeon/radeon_ring.c
index 2430d80b18716b6cd8c338c6fff86c53354992ac..cd72062d5a9134bd596c8a6388b78fd45bb02425 100644 (file)
--- a/drivers/gpu/drm/radeon/radeon_ring.c
+++ b/drivers/gpu/drm/radeon/radeon_ring.c
@@ -377,6 +377,9 @@ int radeon_ring_alloc(struct radeon_device *rdev, struct radeon_ring *ring, unsi
 {
        int r;
 
+       /* make sure we aren't trying to allocate more space than there is on the ring */
+       if (ndw > (ring->ring_size / 4))
+               return -ENOMEM;
        /* Align requested size with padding so unlock_commit can
         * pad safely */
        ndw = (ndw + ring->align_mask) & ~ring->align_mask;