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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Andrew Morton , Willy Tarreau , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Simona Vetter , Chris Wilson , Matthew Auld , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , "Ritesh Harjani (IBM)" , Shrikanth Hegde , Rik van Riel , Benjamin Herrenschmidt , linux-mm@kvack.org, linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linuxppc-dev@lists.ozlabs.org, stable@vger.kernel.org Subject: Re: [PATCH 2/5] drm/i915: consider vm_pgoff in vm_access() Message-ID: References: <20261112-access_shite-v1-0-988a5c470db2@kernel.org> <20261112-access_shite-v1-2-988a5c470db2@kernel.org> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , Precedence: list X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261112-access_shite-v1-2-988a5c470db2@kernel.org> X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS autolearn=unavailable autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Thu, Nov 12, 2026 at 11:08:58PM +0100, David Hildenbrand (Arm) wrote: > vm_access() treats the start of every VMA as the beginning of the GEM > object. After a VMA split, vm_pgoff identifies a later part of the > object. Debugger reads and writes through ptrace or /proc//mem then > access the wrong bytes. > > Properly consider vm_pgoff just like the fault handlers already do. > > Fixes: 9f909e215fea ("drm/i915: Implement vm_ops->access for gdb access into mmaps") > Cc: stable@vger.kernel.org > Signed-off-by: David Hildenbrand (Arm) And since this is an mmap-an-fd driver thing there's no need to worry about anon pgoff etc. Looks sensible to me so: Acked-by: Lorenzo Stoakes (ARM) > --- > drivers/gpu/drm/i915/gem/i915_gem_mman.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c > index 6b337684dbfe8..e3b24dc8e94f5 100644 > --- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c > +++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c > @@ -511,13 +511,15 @@ vm_access(struct vm_area_struct *area, unsigned long addr, > struct i915_mmap_offset *mmo = area->vm_private_data; > struct drm_i915_gem_object *obj = mmo->obj; > struct i915_gem_ww_ctx ww; > + unsigned long obj_offset; > void *vaddr; > int err = 0; > > if (i915_gem_object_is_readonly(obj) && write) > return -EACCES; > > - addr -= area->vm_start; > + obj_offset = area->vm_pgoff - drm_vma_node_start(&mmo->vma_node); > + addr += (obj_offset << PAGE_SHIFT) - area->vm_start; > if (range_overflows_t(u64, addr, len, obj->base.size)) > return -EINVAL; > > > -- > 2.43.0 > -- Cheers, Lorenzo