From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 951A5E9B245 for ; Tue, 24 Feb 2026 09:50:17 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 0F1C310E541; Tue, 24 Feb 2026 09:50:16 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="gcXcUYVC"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.19]) by gabe.freedesktop.org (Postfix) with ESMTPS id 7A81610E539; Tue, 24 Feb 2026 09:50:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1771926614; x=1803462614; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=LE2pGK1fEdEnRioFiZQy8bGXtGZfvqUajV9L7/N1/C4=; b=gcXcUYVCI5Op08HOAw9CGoyS5ccmxp3U7FCHKLwjsofYPcm/gJrNzBZ+ DnFpgKTXpZsnkGWqoSkpWQHRb9yfRHyQVQAyav5e0k4MzCuwOSmxbKqvD 5R9kEqdkPN5lEWNQQEz/hMsCy/jzQCu9KNhUkFxBh5qB3x31ys8tkmSMM 7GMPdbdLpBAqm8S1ufb99I/wmyBe/SEcUl/rAhqaW8KSjEPBI6dgvJqDE 7CTbR7yRiN2eMpSI+sHU9F6mqFgvjDiYa7XOld27hqYQv3+jtARo1MkAn C+BeyJ5yDzTfWJFPYt3lUqvqniq2E6OdaB34lBkRm1alcY43+cuyLG/0e Q==; X-CSE-ConnectionGUID: 0qsYefiDQY2jfE2qAaXibQ== X-CSE-MsgGUID: 1heexYsGRwGY4/7R6oRsVg== X-IronPort-AV: E=McAfee;i="6800,10657,11710"; a="72839671" X-IronPort-AV: E=Sophos;i="6.21,308,1763452800"; d="scan'208";a="72839671" Received: from fmviesa003.fm.intel.com ([10.60.135.143]) by orvoesa111.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Feb 2026 01:50:13 -0800 X-CSE-ConnectionGUID: ME+F9SM7QMC4B6rDFbfkWg== X-CSE-MsgGUID: Z51BegxZQY+Lunaq8VrnTw== X-ExtLoop1: 1 Received: from ettammin-mobl3.ger.corp.intel.com (HELO jkrzyszt-mobl2.intranet) ([10.245.246.26]) by fmviesa003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Feb 2026 01:50:10 -0800 From: Janusz Krzysztofik To: intel-gfx@lists.freedesktop.org Cc: dri-devel@lists.freedesktop.org, Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , Andi Shyti , Andrew Morton , "Matthew Wilcox (Oracle)" , Krzysztof Karas , Sebastian Brzezinka , Krzysztof Niemiec Subject: [PATCH] drm/i915: Fix potential overflow of shmem scatterlist length Date: Tue, 24 Feb 2026 10:49:06 +0100 Message-ID: <20260224094944.2447913-2-janusz.krzysztofik@linux.intel.com> X-Mailer: git-send-email 2.52.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" When a scatterlists table of a GEM shmem object of size 4 GB or more is populated with pages allocated from a folio, unsigned int .length attribute of a scatterlist may get overflowed if total byte length of pages allocated to that single scatterlist happens to reach or cross the 4GB limit. As a consequence, users of the object may suffer from hitting unexpected, premature end of the object's backing pages. [278.780187] ------------[ cut here ]------------ [278.780377] WARNING: CPU: 1 PID: 2326 at drivers/gpu/drm/i915/i915_mm.c:55 remap_sg+0x199/0x1d0 [i915] ... [278.780654] CPU: 1 UID: 0 PID: 2326 Comm: gem_mmap_offset Tainted: G S U 6.17.0-rc1-CI_DRM_16981-ged823aaa0607+ #1 PREEMPT(voluntary) [278.780656] Tainted: [S]=CPU_OUT_OF_SPEC, [U]=USER [278.780658] Hardware name: Intel Corporation Meteor Lake Client Platform/MTL-P LP5x T3 RVP, BIOS MTLPFWI1.R00.3471.D91.2401310918 01/31/2024 [278.780659] RIP: 0010:remap_sg+0x199/0x1d0 [i915] ... [278.780786] Call Trace: [278.780787] [278.780788] ? __apply_to_page_range+0x3e6/0x910 [278.780795] ? __pfx_remap_sg+0x10/0x10 [i915] [278.780906] apply_to_page_range+0x14/0x30 [278.780908] remap_io_sg+0x14d/0x260 [i915] [278.781013] vm_fault_cpu+0xd2/0x330 [i915] [278.781137] __do_fault+0x3a/0x1b0 [278.781140] do_fault+0x322/0x640 [278.781143] __handle_mm_fault+0x938/0xfd0 [278.781150] handle_mm_fault+0x12c/0x300 [278.781152] ? lock_mm_and_find_vma+0x4b/0x760 [278.781155] do_user_addr_fault+0x2d6/0x8e0 [278.781160] exc_page_fault+0x96/0x2c0 [278.781165] asm_exc_page_fault+0x27/0x30 ... That issue was apprehended by the author of a change that introduced it, and potential risk even annotated with a comment, but then never addressed. When adding folio pages to a scatterlist table, take care of byte length of any single scatterlist not exceeding max_segment. Fixes: 0b62af28f249b ("i915: convert shmem_sg_free_table() to use a folio_batch") Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/14809 Cc: Matthew Wilcox (Oracle) Cc: Andrew Morton Cc: stable@vger.kernel.org # v6.5+ Signed-off-by: Janusz Krzysztofik --- drivers/gpu/drm/i915/gem/i915_gem_shmem.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c index c6c64ba29bc42..720a9ad39aa2a 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c @@ -153,8 +153,12 @@ int shmem_sg_alloc_table(struct drm_i915_private *i915, struct sg_table *st, } } while (1); - nr_pages = min_t(unsigned long, - folio_nr_pages(folio), page_count - i); + nr_pages = min_array(((unsigned long[]) { + folio_nr_pages(folio), + page_count - i, + max_segment / PAGE_SIZE, + }), 3); + if (!i || sg->length >= max_segment || folio_pfn(folio) != next_pfn) { @@ -164,7 +168,9 @@ int shmem_sg_alloc_table(struct drm_i915_private *i915, struct sg_table *st, st->nents++; sg_set_folio(sg, folio, nr_pages * PAGE_SIZE, 0); } else { - /* XXX: could overflow? */ + nr_pages = min_t(unsigned long, nr_pages, + (max_segment - sg->length) / PAGE_SIZE); + sg->length += nr_pages * PAGE_SIZE; } next_pfn = folio_pfn(folio) + nr_pages; -- 2.52.0