linux-kernel - [PATCH] drm/imagination: fix off by one in pvr_vm_mips

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Date:   Thu, 30 Nov 2023 10:27:15 +0300
From:   Dan Carpenter <dan.carpenter@...aro.org>
To:     Sarah Walker <sarah.walker@...tec.com>
Cc:     Frank Binns <frank.binns@...tec.com>,
        Donald Robson <donald.robson@...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>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: [PATCH] drm/imagination: fix off by one in pvr_vm_mips_init() error
 handling

If the call to vmap() fails the "page_nr" is one element beyond the end
of the mips_data->pt_dma_addr[] and mips_data->pt_pages[] arrays.

The way that this is traditionally written is that we clean up the
partial loop iteration before the goto and then we can say
while (--i >= 0).  At that point we know that all the elements thus
far are initialized so we don't need to have NULL checks.

Fixes: 927f3e0253c1 ("drm/imagination: Implement MIPS firmware processor and MMU support")
Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
---
 drivers/gpu/drm/imagination/pvr_vm_mips.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/imagination/pvr_vm_mips.c b/drivers/gpu/drm/imagination/pvr_vm_mips.c
index 7268cf6e630b..2bc7181a4c3e 100644
--- a/drivers/gpu/drm/imagination/pvr_vm_mips.c
+++ b/drivers/gpu/drm/imagination/pvr_vm_mips.c
@@ -57,6 +57,7 @@ pvr_vm_mips_init(struct pvr_device *pvr_dev)
 							       PAGE_SIZE, DMA_TO_DEVICE);
 		if (dma_mapping_error(dev, mips_data->pt_dma_addr[page_nr])) {
 			err = -ENOMEM;
+			__free_page(mips_data->pt_pages[page_nr]);
 			goto err_free_pages;
 		}
 	}
@@ -79,13 +80,11 @@ pvr_vm_mips_init(struct pvr_device *pvr_dev)
 	return 0;
 
 err_free_pages:
-	for (; page_nr >= 0; page_nr--) {
-		if (mips_data->pt_dma_addr[page_nr])
-			dma_unmap_page(from_pvr_device(pvr_dev)->dev,
-				       mips_data->pt_dma_addr[page_nr], PAGE_SIZE, DMA_TO_DEVICE);
+	while (--page_nr >= 0) {
+		dma_unmap_page(from_pvr_device(pvr_dev)->dev,
+			       mips_data->pt_dma_addr[page_nr], PAGE_SIZE, DMA_TO_DEVICE);
 
-		if (mips_data->pt_pages[page_nr])
-			__free_page(mips_data->pt_pages[page_nr]);
+		__free_page(mips_data->pt_pages[page_nr]);
 	}
 
 	return err;
-- 
2.42.0