On Thu, Sep 17, 2026 at 02:33:44PM +0200, Boris Brezillon wrote: > Imported BOs have no backing.pages array allocated, leading to a NULL > deref when iova_mapped_as_huge_page() gets called on them. > > Implement this check through and sgt walk to reach the position of the > sgt targeted by a VA, and check that the DMA address is properly aligned > and the size remaining in the SG entry is bigger than a huge page. > This is basically matching the logic in vm_map_pages(), with get_pgsize() > being replaced by a simpler test, because we don't care about the pgcount > info. > > Reported-by: Akash Goel <[email protected]> > Fixes: 8e7460eac786 ("drm/panthor: Support partial unmaps of huge pages") > Signed-off-by: Boris Brezillon <[email protected]>
Reviewed-by: Liviu Dudau <[email protected]> Best regards, Liviu > --- > drivers/gpu/drm/panthor/panthor_mmu.c | 44 > ++++++++++++++++++++++++++++------- > 1 file changed, 36 insertions(+), 8 deletions(-) > > diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c > b/drivers/gpu/drm/panthor/panthor_mmu.c > index b0a7033480e6..6cef954e2cba 100644 > --- a/drivers/gpu/drm/panthor/panthor_mmu.c > +++ b/drivers/gpu/drm/panthor/panthor_mmu.c > @@ -2299,7 +2299,6 @@ iova_mapped_as_huge_page(struct drm_gpuva *mapping, u64 > va) > { > struct panthor_gem_object *bo = to_panthor_bo(mapping->gem.obj); > u64 aligned_va = ALIGN_DOWN(va, SZ_2M); > - const struct page *pg; > pgoff_t bo_offset; > > /* If the 2M-aligned VA is outside the mapping being tested, we know > @@ -2309,16 +2308,45 @@ iova_mapped_as_huge_page(struct drm_gpuva *mapping, > u64 va) > return false; > > bo_offset = aligned_va - mapping->va.addr + mapping->gem.offset; > - pg = bo->backing.pages[bo_offset >> PAGE_SHIFT]; > > - /* In case of shmem backing, we know we can only have a huge mapping > - * if the bo_offset is 2M aligned, meaning we can skip the folio size > - * check if it's not the case. > - */ > - if (!IS_ALIGNED(bo_offset, SZ_2M)) > + if (drm_gem_is_imported(&bo->base)) { > + struct sg_table *sgt = bo->dmap.sgt; > + struct scatterlist *sgl; > + unsigned int count; > + > + /* If this is an imported BO, we have to walk the SGT and > + * check the dma address/size alignment to determine if it's > + * a huge map or not. > + */ > + for_each_sgtable_dma_sg(sgt, sgl, count) { > + size_t len = sg_dma_len(sgl); > + dma_addr_t daddr; > + > + if (len <= bo_offset) { > + bo_offset -= len; > + continue; > + } > + > + len -= bo_offset; > + daddr = sg_dma_address(sgl) + bo_offset; > + > + return IS_ALIGNED(daddr, SZ_2M) && > + len >= SZ_2M; > + } > + > return false; > + } else { > + const struct page *pg = bo->backing.pages[bo_offset >> > PAGE_SHIFT]; > > - return folio_size(page_folio(pg)) >= SZ_2M; > + /* In case of shmem backing, we know we can only have a huge > mapping > + * if the bo_offset is 2M aligned, meaning we can skip the > folio size > + * check if it's not the case. > + */ > + if (!IS_ALIGNED(bo_offset, SZ_2M)) > + return false; > + > + return folio_size(page_folio(pg)) >= SZ_2M; > + } > } > > static void > > -- > 2.55.0 > -- ==================== | I would like to | | fix the world, | | but they're not | | giving me the | \ source code! / --------------- ¯\_(ツ)_/¯
