linux-kernel - [PATCH] drm/via: Add new condition to via_dma

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Date:   Fri, 29 Jul 2022 12:06:43 +0300
From:   Alisa Khabibrakhmanova <khabibrakhmanova@...ras.ru>
To:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Sam Ravnborg <sam@...nborg.org>
Cc:     Alisa Khabibrakhmanova <khabibrakhmanova@...ras.ru>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        ldv-project@...uxtesting.org
Subject: [PATCH] drm/via: Add new condition to via_dma_cleanup()

Pointer dev_priv->mmio, which was checked for NULL at via_do_init_map(),
is passed to via_do_cleanup_map() and is dereferenced there without check.

The patch adds the condition in via_dma_cleanup() which prevents potential NULL
pointer dereference.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 22f579c621e2 ("drm: Add via unichrome support")
Signed-off-by: Alisa Khabibrakhmanova <khabibrakhmanova@...ras.ru>
---
 drivers/gpu/drm/via/via_dri1.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/via/via_dri1.c b/drivers/gpu/drm/via/via_dri1.c
index d695d9291ece..691e3ceb0062 100644
--- a/drivers/gpu/drm/via/via_dri1.c
+++ b/drivers/gpu/drm/via/via_dri1.c
@@ -2961,7 +2961,7 @@ int via_dma_cleanup(struct drm_device *dev)
 		drm_via_private_t *dev_priv =
 		    (drm_via_private_t *) dev->dev_private;
 
-		if (dev_priv->ring.virtual_start) {
+		if (dev_priv->ring.virtual_start && dev_priv->mmio) {
 			via_cmdbuf_reset(dev_priv);
 
 			drm_legacy_ioremapfree(&dev_priv->ring.map, dev);
-- 
2.34.1