[Mesa-dev] [PATCHv2 2/2] util/u_vbuf: correct map offset calculation for crazy offsets

[Ilia Mirkin]

When the min_index is very large (or very negative), the multipliation
can overflow 32 bits and result in an incorrect map pointer
modification.

Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
---

I tested this by setting PIPE_CAP_USER_*_BUFFERS to 0 on nv50, and hacking the
logic to say that unroll_indices = true, running with the
draw-elements-base-vertex-neg user_varrays test.

 src/gallium/auxiliary/util/u_vbuf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/gallium/auxiliary/util/u_vbuf.c b/src/gallium/auxiliary/util/u_vbuf.c
index 52b360e..0c9c349 100644
--- a/src/gallium/auxiliary/util/u_vbuf.c
+++ b/src/gallium/auxiliary/util/u_vbuf.c
@@ -370,7 +370,7 @@ u_vbuf_translate_buffers(struct u_vbuf *mgr, struct translate_key *key,
 
       /* Subtract min_index so that indexing with the index buffer works. */
       if (unroll_indices) {
-         map -= vb->stride * min_index;
+         map -= (ptrdiff_t)vb->stride * min_index;
       }
 
       tr->set_buffer(tr, i, map, vb->stride, ~0);
-- 
1.8.3.2