+ i915-limit-the-length-of-an-sg-list-to-the-requested-length.patch added to mm-hotfixes-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: i915: limit the length of an sg list to the requested length
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     i915-limit-the-length-of-an-sg-list-to-the-requested-length.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/i915-limit-the-length-of-an-sg-list-to-the-requested-length.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Subject: i915: limit the length of an sg list to the requested length
Date: Tue, 19 Sep 2023 20:48:55 +0100

The folio conversion changed the behaviour of shmem_sg_alloc_table() to
put the entire length of the last folio into the sg list, even if the sg
list should have been shorter.  gen8_ggtt_insert_entries() relied on the
list being the right langth and would overrun the end of the page tables. 
Other functions may also have been affected.

Clamp the length of the last entry in the sg list to be the expected
length.

Link: https://lkml.kernel.org/r/20230919194855.347582-1-willy@infradead.org
Link: https://gitlab.freedesktop.org/drm/intel/-/issues/9256
Fixes: 0b62af28f249 ("i915: convert shmem_sg_free_table() to use a folio_batch")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reported-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Closes: https://lore.kernel.org/lkml/6287208.lOV4Wx5bFT@natalenko.name/
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: <stable@vger.kernel.org>	[6.5.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/gpu/drm/i915/gem/i915_gem_shmem.c |   11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

--- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c~i915-limit-the-length-of-an-sg-list-to-the-requested-length
+++ a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
@@ -100,6 +100,7 @@ int shmem_sg_alloc_table(struct drm_i915
 	st->nents = 0;
 	for (i = 0; i < page_count; i++) {
 		struct folio *folio;
+		unsigned long nr_pages;
 		const unsigned int shrink[] = {
 			I915_SHRINK_BOUND | I915_SHRINK_UNBOUND,
 			0,
@@ -150,6 +151,8 @@ int shmem_sg_alloc_table(struct drm_i915
 			}
 		} while (1);
 
+		nr_pages = min_t(unsigned long,
+				folio_nr_pages(folio), page_count - i);
 		if (!i ||
 		    sg->length >= max_segment ||
 		    folio_pfn(folio) != next_pfn) {
@@ -157,13 +160,13 @@ int shmem_sg_alloc_table(struct drm_i915
 				sg = sg_next(sg);
 
 			st->nents++;
-			sg_set_folio(sg, folio, folio_size(folio), 0);
+			sg_set_folio(sg, folio, nr_pages * PAGE_SIZE, 0);
 		} else {
 			/* XXX: could overflow? */
-			sg->length += folio_size(folio);
+			sg->length += nr_pages * PAGE_SIZE;
 		}
-		next_pfn = folio_pfn(folio) + folio_nr_pages(folio);
-		i += folio_nr_pages(folio) - 1;
+		next_pfn = folio_pfn(folio) + nr_pages;
+		i += nr_pages - 1;
 
 		/* Check that the i965g/gm workaround works. */
 		GEM_BUG_ON(gfp & __GFP_DMA32 && next_pfn >= 0x00100000UL);
_

Patches currently in -mm which might be from willy@infradead.org are

i915-limit-the-length-of-an-sg-list-to-the-requested-length.patch
mm-convert-dax-lock-unlock-page-to-lock-unlock-folio.patch
buffer-pass-gfp-flags-to-folio_alloc_buffers.patch
buffer-hoist-gfp-flags-from-grow_dev_page-to-__getblk_gfp.patch
ext4-use-bdev_getblk-to-avoid-memory-reclaim-in-readahead-path.patch
buffer-use-bdev_getblk-to-avoid-memory-reclaim-in-readahead-path.patch
buffer-convert-getblk_unmovable-and-__getblk-to-use-bdev_getblk.patch
buffer-convert-sb_getblk-to-call-__getblk.patch
ext4-call-bdev_getblk-from-sb_getblk_gfp.patch
buffer-remove-__getblk_gfp.patch
hugetlb-use-a-folio-in-free_hpage_workfn.patch
hugetlb-remove-a-few-calls-to-page_folio.patch
hugetlb-convert-remove_pool_huge_page-to-remove_pool_hugetlb_folio.patch