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Tue, 07 Jul 2026 08:05:51 -0700 (PDT) Received: from haichao.tail057a43.ts.net ([2001:da8:e000:1206:239e:a31b:1d0d:374f]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2ccc9bf77e4sm13747065ad.22.2026.07.07.08.05.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Jul 2026 08:05:50 -0700 (PDT) From: Ruoyu Wang To: zack.rusin@broadcom.com, bcm-kernel-feedback-list@broadcom.com, maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de, airlied@gmail.com, simona@ffwll.ch Cc: mombasawalam@vmware.com, krastevm@vmware.com, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Ruoyu Wang Subject: [PATCH] drm/vmwgfx: Handle MOBs without page-table BOs Date: Tue, 7 Jul 2026 23:05:44 +0800 Message-ID: <20260707150544.2272933-1-ruoyuw560@gmail.com> X-Mailer: git-send-email 2.51.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 --- 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