Single-page MOBs and small OTable bases use depth-0 page-table entries
and do not allocate a page-table BO. Their existing teardown paths were
written to tolerate that by checking a local BO pointer before reserving
or fencing it.
Commit 668b206601c5 ("drm/vmwgfx: Stop using raw ttm_buffer_object's")
changed pt_bo from a raw TTM buffer object pointer to a vmwgfx BO pointer
and converted those local BO initializers to &pt_bo->tbo. That
dereferences pt_bo before the existing NULL checks, so depth-0 MOBs can
crash during OTable teardown or MOB unbind.
Keep the previous conditional behavior by deriving the TTM BO only when
the MOB has a page-table BO.
This issue was found by a static analysis checker and confirmed by
manual source review.
Fixes: 668b206601c5 ("drm/vmwgfx: Stop using raw ttm_buffer_object's")
Signed-off-by: Ruoyu Wang <[email protected]>
---
drivers/gpu/drm/vmwgfx/vmwgfx_mob.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_mob.c
b/drivers/gpu/drm/vmwgfx/vmwgfx_mob.c
index de7a504de9ce5..7cfd96e6e3489 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_mob.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_mob.c
@@ -204,7 +204,9 @@ static void vmw_takedown_otable_base(struct vmw_private
*dev_priv,
if (otable->page_table == NULL)
return;
- bo = &otable->page_table->pt_bo->tbo;
+ bo = NULL;
+ if (otable->page_table->pt_bo)
+ bo = &otable->page_table->pt_bo->tbo;
cmd = VMW_CMD_RESERVE(dev_priv, sizeof(*cmd));
if (unlikely(cmd == NULL))
return;
@@ -555,7 +557,10 @@ void vmw_mob_unbind(struct vmw_private *dev_priv,
SVGA3dCmdDestroyGBMob body;
} *cmd;
int ret;
- struct ttm_buffer_object *bo = &mob->pt_bo->tbo;
+ struct ttm_buffer_object *bo = NULL;
+
+ if (mob->pt_bo)
+ bo = &mob->pt_bo->tbo;
if (bo) {
ret = ttm_bo_reserve(bo, false, true, NULL);
--
2.51.0
