swrast: Fix unsigned promotion in pointer arithmetic

When rowstride was negatie, unsigned promotion caused a segfault here:

299│    if (rb->Format == MESA_FORMAT_S8) {
300│       const GLuint rowStride = rb->RowStride;
301│       for (i = 0; i < count; i++) {
302│          if (x[i] >= 0 && y[i] >= 0 && x[i] < w && y[i] < h) {
303├>            stencil[i] = *(map + y[i] * rowStride + x[i]);
304│          }
305│       }
306│    }

Fixes segfault in oglconform
separatestencil-neu(NonPolygon.BothFacesBitmapCoreAPI),
though test still fails.

Note: This is a candidate for the stable branches.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=43327
Reviewed-by: Brian Paul <brianp@vmware.com>
Signed-off-by: Chad Versace <chad.versace@linux.intel.com>
(cherry picked from commit aed5c8299fe47b8e1728f8140d069bc89d3fa947)

1 files changed, 3 insertions, 3 deletions

diff --git a/src/mesa/swrast/s_stencil.c b/src/mesa/swrast/s_stencil.c
index dbcbd2be069..fb95ef14df3 100644
--- a/src/mesa/swrast/s_stencil.c
+++ b/src/mesa/swrast/s_stencil.c
@@ -297,7 +297,7 @@ get_s8_values(struct gl_context *ctx, struct gl_renderbuffer *rb,
    GLuint i;
 
    if (rb->Format == MESA_FORMAT_S8) {
-      const GLuint rowStride = rb->RowStride;
+      const GLint rowStride = rb->RowStride;
       for (i = 0; i < count; i++) {
          if (x[i] >= 0 && y[i] >= 0 && x[i] < w && y[i] < h) {
             stencil[i] = *(map + y[i] * rowStride + x[i]);
@@ -305,8 +305,8 @@ get_s8_values(struct gl_context *ctx, struct gl_renderbuffer *rb,
       }
    }
    else {
-      const GLuint bpp = _mesa_get_format_bytes(rb->Format);
-      const GLuint rowStride = rb->RowStride * bpp;
+      const GLint bpp = _mesa_get_format_bytes(rb->Format);
+      const GLint rowStride = rb->RowStride * bpp;
       for (i = 0; i < count; i++) {
          if (x[i] >= 0 && y[i] >= 0 && x[i] < w && y[i] < h) {
             const GLubyte *src = map + y[i] * rowStride + x[i] * bpp;