drm/radeon: Make r100_cp_ring_info() and radeon_ring_gfx() safe (v2)

Prevent NULL pointer dereference in case when radeon_ring_fini() did it's job.

Reading of r100_cp_ring_info and radeon_ring_gfx debugfs entries will lead to a KP if ring buffer was deallocated, e.g. on failed ring test.
Seen on PA-RISC machine having "radeon: ring test failed (scratch(0x8504)=0xCAFEDEAD)" issue.

v2: agd5f: add some parens around ring->ready check

Signed-off-by: Alex Ivanov <gnidorah@p0n4ik.tk>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

1 files changed, 5 insertions, 3 deletions

diff --git a/drivers/gpu/drm/radeon/radeon_ring.c b/drivers/gpu/drm/radeon/radeon_ring.c
index 46a25f037b84..18254e1c3e71 100644
--- a/drivers/gpu/drm/radeon/radeon_ring.c
+++ b/drivers/gpu/drm/radeon/radeon_ring.c
@@ -839,9 +839,11 @@ static int radeon_debugfs_ring_info(struct seq_file *m, void *data)
          * packet that is the root issue
          */
         i = (ring->rptr + ring->ptr_mask + 1 - 32) & ring->ptr_mask;
-        for (j = 0; j <= (count + 32); j++) {
-                seq_printf(m, "r[%5d]=0x%08x\n", i, ring->ring[i]);
-                i = (i + 1) & ring->ptr_mask;
+        if (ring->ready) {
+                for (j = 0; j <= (count + 32); j++) {
+                        seq_printf(m, "r[%5d]=0x%08x\n", i, ring->ring[i]);
+                        i = (i + 1) & ring->ptr_mask;
+                }
         }
         return 0;
 }