drm/panfrost: Fix the error path in panfrost_mmu_map_fault_addr()

If some the pages or sgt allocation failed, we shouldn't release the
pages ref we got earlier, otherwise we will end up with unbalanced
get/put_pages() calls. We should instead leave everything in place
and let the BO release function deal with extra cleanup when the object
is destroyed, or let the fault handler try again next time it's called.

Fixes: 187d292 ("drm/panfrost: Add support for GPU heap allocations")
Cc: <[email protected]>
Reviewed-by: Steven Price <[email protected]>
Reviewed-by: AngeloGioacchino Del Regno <[email protected]>
Signed-off-by: Boris Brezillon <[email protected]>
Co-developed-by: Dmitry Osipenko <[email protected]>
Signed-off-by: Dmitry Osipenko <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

CVE-2024-35951
(backported from commit 1fc9af8)
[hui: This fix commit can't be cleanly applied to J and F due to
 missing a prerequisite commit 21aa27d ("drm/shmem-helper: Switch
 to reservation lock"), the prerequisite commit will introduce a
 significant change hence here can't introduce it in the J and F. So
 I edited the fix commit accordingly, changed "goto err_unlock" to
 "goto err_bo".]
Signed-off-by: Hui Wang <[email protected]>
Acked-by: Mehmet Basaran <[email protected]>
Acked-by: Chris Chiu <[email protected]>
Signed-off-by: Stefan Bader <[email protected]>

Author: bbrezillon

drivers/gpu/drm/panfrost/panfrost_mmu.c

@@ -465,12 +465,19 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
 	mapping_set_unevictable(mapping);
 
 	for (i = page_offset; i < page_offset + NUM_FAULT_PAGES; i++) {
+		/* Can happen if the last fault only partially filled this
+		 * section of the pages array before failing. In that case
+		 * we skip already filled pages.
+		 */
+		if (pages[i])
+			continue;
+
 		pages[i] = shmem_read_mapping_page(mapping, i);
 		if (IS_ERR(pages[i])) {
 			mutex_unlock(&bo->base.pages_lock);
 			ret = PTR_ERR(pages[i]);
 			pages[i] = NULL;
-			goto err_pages;
+			goto err_bo;
 		}
 	}
 
@@ -480,7 +487,7 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
 	ret = sg_alloc_table_from_pages(sgt, pages + page_offset,
 					NUM_FAULT_PAGES, 0, SZ_2M, GFP_KERNEL);
 	if (ret)
-		goto err_pages;
+		goto err_bo;
 
 	ret = dma_map_sgtable(pfdev->dev, sgt, DMA_BIDIRECTIONAL, 0);
 	if (ret)
@@ -500,8 +507,6 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
 
 err_map:
 	sg_free_table(sgt);
-err_pages:
-	drm_gem_shmem_put_pages(&bo->base);
 err_bo:
 	panfrost_gem_mapping_put(bomapping);
 	return ret;