linux-kernel - [PATCH] drm/imagination: Move dereference after NULL check in pvr_mmu_backing_page

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Message-ID: <13f4278e-af9c-4092-9196-bc0e6b76f1eb@moroto.mountain>
Date:   Wed, 6 Dec 2023 17:37:24 +0300
From:   Dan Carpenter <dan.carpenter@...aro.org>
To:     Donald Robson <donald.robson@...tec.com>
Cc:     Frank Binns <frank.binns@...tec.com>,
        Matt Coster <matt.coster@...tec.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Sarah Walker <sarah.walker@...tec.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: [PATCH] drm/imagination: Move dereference after NULL check in
 pvr_mmu_backing_page_init()

This code dereferences "page->pvr_dev" and then checked for NULL on the
next line.  Re-order it to avoid a potential NULL pointer dereference.

Fixes: ff5f643de0bf ("drm/imagination: Add GEM and VM related code")
Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
---
 drivers/gpu/drm/imagination/pvr_mmu.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/imagination/pvr_mmu.c b/drivers/gpu/drm/imagination/pvr_mmu.c
index c8562bfc0dcd..4fe70610ed94 100644
--- a/drivers/gpu/drm/imagination/pvr_mmu.c
+++ b/drivers/gpu/drm/imagination/pvr_mmu.c
@@ -316,12 +316,14 @@ pvr_mmu_backing_page_init(struct pvr_mmu_backing_page *page,
 static void
 pvr_mmu_backing_page_fini(struct pvr_mmu_backing_page *page)
 {
-	struct device *dev = from_pvr_device(page->pvr_dev)->dev;
+	struct device *dev;
 
 	/* Do nothing if no allocation is present. */
 	if (!page->pvr_dev)
 		return;
 
+	dev = from_pvr_device(page->pvr_dev)->dev;
+
 	dma_unmap_page(dev, page->dma_addr, PVR_MMU_BACKING_PAGE_SIZE,
 		       DMA_TO_DEVICE);
 
-- 
2.42.0