From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C90EA607351C for ; Tue, 27 Oct 2026 15:48:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=gBef+ldf Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 2AC9A10F6A9; Tue, 27 Oct 2026 15:48:05 +0000 (UTC) Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by gabe.freedesktop.org (Postfix) with ESMTPS id 9CBA510F5CD for ; Tue, 27 Oct 2026 15:47:58 +0000 (UTC) Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id D021E60A8C; Tue, 27 Oct 2026 15:47:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6973B1F01147; Tue, 27 Oct 2026 15:47:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793116077; bh=kdztsirRHY2cmeIGfuJBYbtzmLZFIzGx9YQE2NB+KFs=; h=From:Subject:Reply-To:To:In-Reply-To:References:Date; b=gBef+ldfmctw4TXpJ9L3Pe9f76uBjHCHLkzIxx6I32i43+v8cOvTEMtKYkWC21prH cWif/0ln4XbTryx5mKi9bgQgvwb3c2CkfpfxLMZAjUWKpbVQaZXqQx3gFMoDNsQXQc Q4jLtnsAHGl4rmsOS6hz9cUR5TqXMjbUrUk7ufPFuewByQFHZG+NsUPOLd5t8J9ByW kKPurBI0p4p94xqatrmBhrF/sy/pcexLT+t/VRSeRTBX2r4pXpBdQvOP9R1t4Q0IyV hWGfF1lUiGtgDeirrt8axkR9st6YtVAPnBFuNdu7X+B1IDYXGn5JC7Rc4rAnnHj2Km pVd3vllYFaRFA== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH v2 2/5] drm/msm/gem: dma_map/unmap_sgtable() To: "Rob Clark" , dri-devel@lists.freedesktop.org In-Reply-To: <20261027152821.51144-3-robin.clark@oss.qualcomm.com> References: <20261027152821.51144-1-robin.clark@oss.qualcomm.com> <20261027152821.51144-3-robin.clark@oss.qualcomm.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Tue, 27 Oct 2026 15:47:57 +0000 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: sashiko-reviews@lists.linux.dev Sender: "dri-devel" X-Spam-Status: No, score=-11.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 X-Archived-By: Thank you for your contribution! Sashiko AI review found 2 potential issue(= s) to consider: - [High] drm/msm: NULL deref in get_pages() error path via drm_prime_gem_de= stroy() - [High] drm/msm: double dma_map/unmap_sgtable() in get_pages() and put_pag= es() -- commit 5b4a3d83276519e9cb8831bdfa37a513b1d334a3 Author: Rob Clark drm/msm/gem: dma_map/unmap_sgtable() This commit adds dma_map_sgtable() and dma_unmap_sgtable() calls in get_pages() and put_pages() to populate the sgtable's dma_address and dma_len fields for setting up pagetable mappings. > diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c > index 181b9ad326729..72e3cd8bb1e7c 100644 > --- a/drivers/gpu/drm/msm/msm_gem.c > +++ b/drivers/gpu/drm/msm/msm_gem.c > @@ -219,6 +219,15 @@ static struct page **get_pages(struct drm_gem_object= *obj) > goto error; > } > =20 > + ret =3D dma_map_sgtable(drm_dev_dma_dev(obj->dev), > + msm_obj->sgt, > + DMA_BIDIRECTIONAL, > + DMA_ATTR_SKIP_CPU_SYNC); > + if (ret) { > + DRM_DEV_ERROR(dev->dev, "could not map sgtable: %d\n", ret); > + goto error; > + } > + > update_device_mem(dev->dev_private, obj->size); > =20 > /* For non-cached buffers, ensure the new pages are clean > @@ -233,6 +242,8 @@ static struct page **get_pages(struct drm_gem_object = *obj) > return msm_obj->pages; > =20 > error: > + if (!IS_ERR(msm_obj->sgt)) > + drm_prime_gem_destroy(obj, msm_obj->sgt); [Severity: High] Will calling drm_prime_gem_destroy() here dereference a NULL pointer and leak msm_obj->sgt when dma_map_sgtable() fails? At the start of get_pages(), imported DMA-BUF objects are rejected: drivers/gpu/drm/msm/msm_gem.c:get_pages() if (drm_WARN_ON_ONCE(obj->dev, drm_gem_is_imported(obj))) return ERR_PTR(-EINVAL); Because get_pages() only runs on native GEM objects, obj->import_attach is always NULL and msm_obj->sgt is allocated via drm_prime_pages_to_sg(). If dma_map_sgtable() fails and jumps to error, drm_prime_gem_destroy() is called with a valid msm_obj->sgt, which then dereferences attach (NULL) at attach->dmabuf while obj->resv is held, and fails to free msm_obj->sgt: drivers/gpu/drm/drm_prime.c:drm_prime_gem_destroy() attach =3D obj->import_attach; if (sg) dma_buf_unmap_attachment_unlocked(attach, sg, DMA_BIDIRECTIONAL); dma_buf =3D attach->dmabuf; Should the error path instead free msm_obj->sgt with sg_free_table(msm_obj->sgt) and kfree(msm_obj->sgt) to match put_pages()? > msm_obj->sgt =3D NULL; > =20 > drm_gem_put_pages(obj, msm_obj->pages, false, false); > @@ -260,6 +271,11 @@ static void put_pages(struct drm_gem_object *obj) > if (msm_obj->flags & MSM_BO_WC) > sync_for_cpu(msm_obj); > =20 > + dma_unmap_sgtable(drm_dev_dma_dev(obj->dev), > + msm_obj->sgt, > + DMA_BIDIRECTIONAL, > + DMA_ATTR_SKIP_CPU_SYNC); [Severity: High] Does this map and unmap msm_obj->sgt twice whenever MSM_BO_WC is set? In get_pages(), right after dma_map_sgtable() maps msm_obj->sgt with DMA_ATTR_SKIP_CPU_SYNC, objects with MSM_BO_WC call sync_for_device(): drivers/gpu/drm/msm/msm_gem.c:get_pages() if (msm_obj->flags & MSM_BO_WC) sync_for_device(msm_obj); And in put_pages(), before the new dma_unmap_sgtable() call, MSM_BO_WC objects call sync_for_cpu(). However, sync_for_device() and sync_for_cpu() themselves call dma_map_sgtable() and dma_unmap_sgtable() on the same msm_obj->sgt and device: drivers/gpu/drm/msm/msm_gem.c: static void sync_for_device(struct msm_gem_object *msm_obj) { struct device *dev =3D msm_obj->base.dev->dev; dma_map_sgtable(dev, msm_obj->sgt, DMA_BIDIRECTIONAL, 0); } static void sync_for_cpu(struct msm_gem_object *msm_obj) { struct device *dev =3D msm_obj->base.dev->dev; dma_unmap_sgtable(dev, msm_obj->sgt, DMA_BIDIRECTIONAL, 0); } On platforms where the top-level DRM device uses IOMMU DMA ops or SWIOTLB, the second dma_map_sgtable() call in sync_for_device() overwrites sg_dma_address and sg_dma_len, leaking the first IOVA or bounce mapping, while put_pages() unmaps and frees the second range twice. With CONFIG_DMA_API_DEBUG enabled, this also triggers overlapping mapping and double unmap warnings. Should sync_for_device() and sync_for_cpu() use dma_sync_sgtable_for_device= () and dma_sync_sgtable_for_cpu() (or fold the CPU sync attribute into the map and unmap calls in get_pages() and put_pages()) instead of mapping and unmapping msm_obj->sgt a second time? --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261027152821.5114= 4-1-robin.clark@oss.qualcomm.com?part=3D2