[REGRESSION] BUG: KFENCE: memory corruption in drm_gem_put_pages+0x186/0x250
Oleksandr Natalenko
oleksandr at natalenko.name
Thu Oct 5 13:34:41 UTC 2023
On čtvrtek 5. října 2023 15:05:27 CEST Matthew Wilcox wrote:
> On Thu, Oct 05, 2023 at 02:30:55PM +0200, Oleksandr Natalenko wrote:
> > No-no, sorry for possible confusion. Let me explain again:
> >
> > 1. we had an issue with i915, which was introduced by 0b62af28f249, and later was fixed by 863a8eb3f270
> > 2. now I've discovered another issue, which looks very similar to 1., but in a VM with Cirrus VGA, and it happens even while having 863a8eb3f270 applied
> > 3. I've tried reverting 3291e09a4638, after which I cannot reproduce the issue with Cirrus VGA, but clearly there was no fix for it discussed
> >
> > IOW, 863a8eb3f270 is the fix for 0b62af28f249, but not for 3291e09a4638. It looks like 3291e09a4638 requires a separate fix.
>
> Thank you! Sorry about the misunderstanding. Try this:
>
> diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> index 6129b89bb366..44a948b80ee1 100644
> --- a/drivers/gpu/drm/drm_gem.c
> +++ b/drivers/gpu/drm/drm_gem.c
> @@ -540,7 +540,7 @@ struct page **drm_gem_get_pages(struct drm_gem_object *obj)
> struct page **pages;
> struct folio *folio;
> struct folio_batch fbatch;
> - int i, j, npages;
> + long i, j, npages;
>
> if (WARN_ON(!obj->filp))
> return ERR_PTR(-EINVAL);
> @@ -564,11 +564,13 @@ struct page **drm_gem_get_pages(struct drm_gem_object *obj)
>
> i = 0;
> while (i < npages) {
> + long nr;
> folio = shmem_read_folio_gfp(mapping, i,
> mapping_gfp_mask(mapping));
> if (IS_ERR(folio))
> goto fail;
> - for (j = 0; j < folio_nr_pages(folio); j++, i++)
> + nr = min(npages - i, folio_nr_pages(folio));
> + for (j = 0; j < nr; j++, i++)
> pages[i] = folio_file_page(folio, i);
>
> /* Make sure shmem keeps __GFP_DMA32 allocated pages in the
No issues after five reboots with this patch applied on top of v6.5.5.
Reported-by: Oleksandr Natalenko <oleksandr at natalenko.name>
Tested-by: Oleksandr Natalenko <oleksandr at natalenko.name>
Link: https://lore.kernel.org/lkml/13360591.uLZWGnKmhe@natalenko.name/
Fixes: 3291e09a4638 ("drm: convert drm_gem_put_pages() to use a folio_batch")
Cc: stable at vger.kernel.org # 6.5.x
Thank you!
--
Oleksandr Natalenko (post-factum)
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