diff options
| author | Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com> | 2026-02-24 10:49:06 +0100 |
|---|---|---|
| committer | Tvrtko Ursulin <tursulin@ursulin.net> | 2026-03-10 08:11:31 +0000 |
| commit | 029ae067431ab9d0fca479bdabe780fa436706ea (patch) | |
| tree | 932d022ef1a7f3d10b8c21e2ec481377ea6f8f61 /drivers/gpu/drm | |
| parent | 237aab549676288d9255bb8dcc284738e56eaa31 (diff) | |
drm/i915: Fix potential overflow of shmem scatterlist length
When a scatterlists table of a GEM shmem object of size 4 GB or more is
populated with pages allocated from a folio, unsigned int .length
attribute of a scatterlist may get overflowed if total byte length of
pages allocated to that single scatterlist happens to reach or cross the
4GB limit. As a consequence, users of the object may suffer from hitting
unexpected, premature end of the object's backing pages.
[278.780187] ------------[ cut here ]------------
[278.780377] WARNING: CPU: 1 PID: 2326 at drivers/gpu/drm/i915/i915_mm.c:55 remap_sg+0x199/0x1d0 [i915]
...
[278.780654] CPU: 1 UID: 0 PID: 2326 Comm: gem_mmap_offset Tainted: G S U 6.17.0-rc1-CI_DRM_16981-ged823aaa0607+ #1 PREEMPT(voluntary)
[278.780656] Tainted: [S]=CPU_OUT_OF_SPEC, [U]=USER
[278.780658] Hardware name: Intel Corporation Meteor Lake Client Platform/MTL-P LP5x T3 RVP, BIOS MTLPFWI1.R00.3471.D91.2401310918 01/31/2024
[278.780659] RIP: 0010:remap_sg+0x199/0x1d0 [i915]
...
[278.780786] Call Trace:
[278.780787] <TASK>
[278.780788] ? __apply_to_page_range+0x3e6/0x910
[278.780795] ? __pfx_remap_sg+0x10/0x10 [i915]
[278.780906] apply_to_page_range+0x14/0x30
[278.780908] remap_io_sg+0x14d/0x260 [i915]
[278.781013] vm_fault_cpu+0xd2/0x330 [i915]
[278.781137] __do_fault+0x3a/0x1b0
[278.781140] do_fault+0x322/0x640
[278.781143] __handle_mm_fault+0x938/0xfd0
[278.781150] handle_mm_fault+0x12c/0x300
[278.781152] ? lock_mm_and_find_vma+0x4b/0x760
[278.781155] do_user_addr_fault+0x2d6/0x8e0
[278.781160] exc_page_fault+0x96/0x2c0
[278.781165] asm_exc_page_fault+0x27/0x30
...
That issue was apprehended by the author of a change that introduced it,
and potential risk even annotated with a comment, but then never addressed.
When adding folio pages to a scatterlist table, take care of byte length
of any single scatterlist not exceeding max_segment.
Fixes: 0b62af28f249b ("i915: convert shmem_sg_free_table() to use a folio_batch")
Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/14809
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: stable@vger.kernel.org # v6.5+
Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://lore.kernel.org/r/20260224094944.2447913-2-janusz.krzysztofik@linux.intel.com
(cherry picked from commit 06249b4e691a75694c014a61708c007fb5755f60)
Signed-off-by: Tvrtko Ursulin <tursulin@ursulin.net>
Diffstat (limited to 'drivers/gpu/drm')
| -rw-r--r-- | drivers/gpu/drm/i915/gem/i915_gem_shmem.c | 12 |
1 files changed, 9 insertions, 3 deletions
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c index c6c64ba29bc4..720a9ad39aa2 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c @@ -153,8 +153,12 @@ int shmem_sg_alloc_table(struct drm_i915_private *i915, struct sg_table *st, } } while (1); - nr_pages = min_t(unsigned long, - folio_nr_pages(folio), page_count - i); + nr_pages = min_array(((unsigned long[]) { + folio_nr_pages(folio), + page_count - i, + max_segment / PAGE_SIZE, + }), 3); + if (!i || sg->length >= max_segment || folio_pfn(folio) != next_pfn) { @@ -164,7 +168,9 @@ int shmem_sg_alloc_table(struct drm_i915_private *i915, struct sg_table *st, st->nents++; sg_set_folio(sg, folio, nr_pages * PAGE_SIZE, 0); } else { - /* XXX: could overflow? */ + nr_pages = min_t(unsigned long, nr_pages, + (max_segment - sg->length) / PAGE_SIZE); + sg->length += nr_pages * PAGE_SIZE; } next_pfn = folio_pfn(folio) + nr_pages; |