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Mon, 9 Feb 2026 15:10:57 +0100 (CET) Date: Mon, 9 Feb 2026 15:10:53 +0100 From: Boris Brezillon To: Thomas Zimmermann Cc: loic.molinari@collabora.com, willy@infradead.org, frank.binns@imgtec.com, matt.coster@imgtec.com, maarten.lankhorst@linux.intel.com, mripard@kernel.org, airlied@gmail.com, simona@ffwll.ch, dri-devel@lists.freedesktop.org, linux-mm@kvack.org Subject: Re: [PATCH v3 2/6] drm/gem-shmem: Test for existence of page in mmap fault handler Message-ID: <20260209151053.397844d9@fedora> In-Reply-To: <20260209133241.238813-3-tzimmermann@suse.de> References: <20260209133241.238813-1-tzimmermann@suse.de> <20260209133241.238813-3-tzimmermann@suse.de> Organization: Collabora X-Mailer: Claws Mail 4.3.1 (GTK 3.24.51; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 966771C0014 X-Stat-Signature: o5i9g55tngbjhjwf98oan1okfb75xfey X-Rspam-User: X-HE-Tag: 1770646260-570803 X-HE-Meta: U2FsdGVkX18gWvAuMxphy7PTLFlzfhOZzZXLNI1Dr2gQ6tqFEdUcsCSND5p0dHVGJor1jNCi7nE7gtP6U9cMXE2L+4bTlpbbqY9iAOQ3+cjFsA6kE0De4HKVxtx4cgmclNti9r6HjEDj2lQglODhCGgCTBHX/FraOQGUq4dvzHXS9eZvlWVQ4sTnIfqXX62kTX6Vj+Arnu+XEvwOtn8vjLOtxych0/mjuM9BEHByPfs5M+UfnOdI9YNpbpbDfwF/52l853q1Si/HCTCXzLmhBowCM84BgHZ3UEufTnEX6h5czXjjrWa9wXCke9mwyYAt57PP2OgGSAItMsgWC/cQ9AmsNutd9WSWPEXwUDYb0X97UeNg9T8bul2o0BRrq3VZnibs8A5Tk38aZcSg0PyGexk+skdzNEyamj+MzS8P/nlEvaK3/2GBYRRwD86q4EPvgJT2s8VdKESJIGVkhNm2XAAmPrw63snq8dmFqotJCi6SwtEHpo0aP45PmwM+Tt0SNhrcQzzkv7Jlcr7Sv7tzKDoRKS1Y0Q3iAZfZ3UYSZjVIpHckG9Hq8/sZJbNN/4/FnO8Cux3Wc9+1wJUDqXaw9YF7iWNBnDa1AKA/iT45rIWEZSK3dVcmpyI4yo6PvanTPQDMwZmfBThTDu+6zQFap1ciujlfsCJmC6H5htiRXAQTbAFf/FxKgaAUC0IkGDZD8MaOM8X17XaLhMwsKkXFfgorQcSKmT+0uioKCZTLQh5GbrhDlMhul5VOj7jGZ4KUcaKyJ1qV/CCoGpRzvt22uCCztiLJrKhnYA9+NwKxcHqzJA6osA6YheGz5DZqFqotZ6LfShD8yByOawWszsSdfF7dBENyivHCcycqg39dNtRVw/d0+keF7t9xCwPAWfzFIGQ2czdi2qjhTSqEAd4fP+eWx5346VD2QYSqVEp1F0bMNmxelCaZYLWivVtdI/AnuyNb0lSar4JdSEInOOr Yvg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 9 Feb 2026 14:27:11 +0100 Thomas Zimmermann wrote: > Not having a page pointer in the mmap fault handler is an error. Test > for this situation and return VM_FAULT_SIGBUS if so. Also replace several > lookups of the page with a local variable. > > Signed-off-by: Thomas Zimmermann Reviewed-by: Boris Brezillon > --- > drivers/gpu/drm/drm_gem_shmem_helper.c | 24 ++++++++++++------------ > 1 file changed, 12 insertions(+), 12 deletions(-) > > diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c > index 5bced7db0f1f..3ee54c24e535 100644 > --- a/drivers/gpu/drm/drm_gem_shmem_helper.c > +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c > @@ -574,31 +574,31 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf) > { > struct vm_area_struct *vma = vmf->vma; > struct drm_gem_object *obj = vma->vm_private_data; > + struct drm_device *dev = obj->dev; > struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj); > loff_t num_pages = obj->size >> PAGE_SHIFT; > - vm_fault_t ret; > + vm_fault_t ret = VM_FAULT_SIGBUS; > struct page **pages = shmem->pages; > - pgoff_t page_offset; > + pgoff_t page_offset = vmf->pgoff - vma->vm_pgoff; /* page offset within VMA */ > + struct page *page; > unsigned long pfn; > > - /* Offset to faulty address in the VMA. */ > - page_offset = vmf->pgoff - vma->vm_pgoff; > - > dma_resv_lock(obj->resv, NULL); > > - if (page_offset >= num_pages || > - drm_WARN_ON_ONCE(obj->dev, !shmem->pages) || > - shmem->madv < 0) { > - ret = VM_FAULT_SIGBUS; > + if (page_offset >= num_pages || drm_WARN_ON_ONCE(dev, !shmem->pages) || > + shmem->madv < 0) > + goto out; > + > + page = pages[page_offset]; > + if (drm_WARN_ON_ONCE(dev, !page)) > goto out; > - } > > - if (drm_gem_shmem_try_map_pmd(vmf, vmf->address, pages[page_offset])) { > + if (drm_gem_shmem_try_map_pmd(vmf, vmf->address, page)) { > ret = VM_FAULT_NOPAGE; > goto out; > } > > - pfn = page_to_pfn(pages[page_offset]); > + pfn = page_to_pfn(page); > ret = vmf_insert_pfn(vma, vmf->address, pfn); > > out: