From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C7C6F2DFF04; Sun, 7 Jun 2026 10:52:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780829568; cv=none; b=EoEfSNzWq5mDvh9nMKVMXf5NulUmnLLMw1jiofY76hLb8tDMiyhipzzGVOC1v3yXvGxozq/GsrfjPB0q+19IzzPbib6VK6+1J9mzZ6RfRmplqS0FFL/oghkQkGkNhkQcReqrctAGoHkVbW5i8nqax3SpKHEUQJPiELZ2V9HpxEA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780829568; c=relaxed/simple; bh=pxJX/JsWC5HAeMMfnd20uGzG08+OM0UT+PeeHQvjNh0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=TXyHLf12eSbHgtOvtIOa+a/vffRkMB/purN78rL88KYQJRPqccjLs12q2qJf9F8W1SvK4USVcWtd20z4ncpMPuFNde2w2GbsRNpU6tPy3grVGGHY5YQtcT22gXHtzCh1EQ4KtPWjWggtvIkBFHKdhS5znXjlnAxobvZ/Mm+EsfM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=lDmV3DWB; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="lDmV3DWB" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 15F441F00893; Sun, 7 Jun 2026 10:52:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1780829566; bh=Rt7tj4qPWZi1wTHopfLFd/sEiUKD/do6s79fYHUQ1cQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=lDmV3DWByYWRaeYsWia0IDs/MA+aLrCK7LZtH1zZEZYukSp4SY5GUSnrzUnc4VAN0 YiRgxuXxEocQif8W2NkRNMGjFkd6iY4NwPMLOv+8hQ6NhgSiYjRWKBwpkVOx5ayqV8 xr16lV0iNvtJIswDhB/wGG/KrKZjeIm7e3En/fBE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Janusz Krzysztofik , Matthew Auld , =?UTF-8?q?Thomas=20Hellstr=C3=B6m?= , Sebastian Brzezinka , =?UTF-8?q?Christian=20K=C3=B6nig?= , Andi Shyti , Tvrtko Ursulin Subject: [PATCH 6.18 259/315] drm/i915: Fix potential UAF in TTM object purge Date: Sun, 7 Jun 2026 12:00:46 +0200 Message-ID: <20260607095737.078610238@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260607095727.528828913@linuxfoundation.org> References: <20260607095727.528828913@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Janusz Krzysztofik commit 5c4063c87a619e4df954c179d24628636f5db15f upstream. TLDR: The bo->ttm object might be changed by calling ttm_bo_validate(), move casting it to an i915_tt object later to actually get the right pointer. A user reported hitting the following bug under heavy use on DG2: [26620.095550] Oops: general protection fault, probably for non-canonical address 0xa56b6b6b6b6b6b8b: 0000 1 SMP NOPTI [26620.095556] CPU: 2 UID: 0 PID: 631 Comm: Xorg Not tainted 6.18.8 #1 PREEMPT(lazy) [26620.095558] Hardware name: ASRock B850M Steel Legend WiFi/B850M Steel Legend WiFi, BIOS 3.50 09/18/2025 [26620.095559] RIP: 0010:i915_ttm_purge+0x84/0x100 [i915] [26620.095604] Code: 00 00 00 48 8d 54 24 10 48 89 e6 48 89 fb e8 83 aa ae ff 85 c0 75 6f 48 83 bb a8 01 00 00 00 74 2c 48 8b 45 78 48 85 c0 74 23 <48> 8b 78 20 48 c7 c2 ff ff ff ff 31 f6 e8 7a 73 e3 e0 48 8b 7d 78 [26620.095605] RSP: 0018:ffffc90005fd7430 EFLAGS: 00010282 [26620.095607] RAX: a56b6b6b6b6b6b6b RBX: ffff8881f46c3dc0 RCX: 0000000000000000 [26620.095608] RDX: 0000000000000000 RSI: 0000000000000246 RDI: 00000000ffffffff [26620.095609] RBP: ffff888289610f00 R08: 0000000000000001 R09: ffff88823b022000 [26620.095609] R10: ffff888103029b28 R11: ffff8881fc7f3800 R12: ffff88810b6150d0 [26620.095609] R13: ffff888289610f00 R14: 0000000000000000 R15: ffff8881f46c3dc0 [26620.095610] FS: 00007f1004d86900(0000) GS:ffff88901c858000(0000) knlGS:0000000000000000 [26620.095611] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [26620.095611] CR2: 00007f0fdf489000 CR3: 000000035b0c1000 CR4: 0000000000750ef0 [26620.095612] PKRU: 55555554 [26620.095612] Call Trace: [26620.095615] [26620.095615] i915_ttm_move+0x2b9/0x420 [i915] [26620.095642] ? ttm_tt_init+0x65/0x80 [ttm] [26620.095644] ? i915_ttm_tt_create+0xc6/0x150 [i915] [26620.095667] ttm_bo_handle_move_mem+0xb6/0x160 [ttm] [26620.095669] ttm_bo_evict+0x100/0x150 [ttm] [26620.095671] ? preempt_count_add+0x64/0xa0 [26620.095673] ? _raw_spin_lock+0xe/0x30 [26620.095675] ? _raw_spin_unlock+0xd/0x30 [26620.095675] ? i915_gem_object_evictable+0xb7/0xd0 [i915] [26620.095704] ttm_bo_evict_cb+0x6e/0xd0 [ttm] [26620.095705] ttm_lru_walk_for_evict+0xa6/0x200 [ttm] [26620.095708] ttm_bo_alloc_resource+0x185/0x4f0 [ttm] [26620.095709] ? init_object+0x62/0xd0 [26620.095712] ttm_bo_validate+0x7a/0x180 [ttm] [26620.095713] ? _raw_spin_unlock_irqrestore+0x16/0x30 [26620.095714] __i915_ttm_get_pages+0xb0/0x170 [i915] [26620.095737] i915_ttm_get_pages+0x9f/0x150 [i915] [26620.095759] ? i915_gem_do_execbuffer+0xedc/0x2b40 [i915] [26620.095786] ? alloc_debug_processing+0xd0/0x100 [26620.095787] ? _raw_spin_unlock_irqrestore+0x16/0x30 [26620.095788] ? i915_vma_instance+0xa0/0x4e0 [i915] [26620.095822] __i915_gem_object_get_pages+0x2f/0x40 [i915] [26620.095848] i915_vma_pin_ww+0x706/0x980 [i915] [26620.095875] ? i915_gem_do_execbuffer+0xedc/0x2b40 [i915] [26620.095904] eb_validate_vmas+0x170/0xa00 [i915] [26620.095930] i915_gem_do_execbuffer+0x1201/0x2b40 [i915] [26620.095953] ? alloc_debug_processing+0xd0/0x100 [26620.095954] ? _raw_spin_unlock_irqrestore+0x16/0x30 [26620.095955] ? i915_gem_execbuffer2_ioctl+0xc9/0x240 [i915] [26620.095977] ? __wake_up_sync_key+0x32/0x50 [26620.095979] ? i915_gem_execbuffer2_ioctl+0xc9/0x240 [i915] [26620.096001] ? __slab_alloc.isra.0+0x67/0xc0 [26620.096003] i915_gem_execbuffer2_ioctl+0x11a/0x240 [i915] Results from decode_stacktrace.sh pointed to dereference of a file pointer field of a i915 TTM page vector container associated with an object being purged on eviction. That path is taken when the object is marked as no longer needed. Code analysis revealed a possibility of the i915 TTM page vector container being replaced with a new instance inside a function that purges content of the object, should it be still busy. That function is called, indirectly via a more general function that changes the object's placement and caching policy, before the problematic dereference, but still after a pointer to the container is captured, rendering the pointer no longer valid. Fix the issue by capturing the pointer to the container only after its potential replacement. v2: Move the container_of() inside the if block (Sebastian), - a simplified version of the commit description that explains briefly why the change is necessary (Christian). Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/work_items/14882 Fixes: 7ae034590ceae ("drm/i915/ttm: add tt shmem backend") Signed-off-by: Janusz Krzysztofik Cc: stable@vger.kernel.org # v5.17+ Cc: Matthew Auld Cc: Thomas Hellström Cc: Sebastian Brzezinka Cc: Christian König Reviewed-by: Andi Shyti Reviewed-by: Christian König Signed-off-by: Andi Shyti Link: https://lore.kernel.org/r/20260508122612.469227-2-janusz.krzysztofik@linux.intel.com (cherry picked from commit 4462966a93eb185849b7f174f0d0de53476d00a4) Signed-off-by: Tvrtko Ursulin Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 28 ++++++++++++++++------------ 1 file changed, 16 insertions(+), 12 deletions(-) --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c @@ -416,8 +416,6 @@ void i915_ttm_free_cached_io_rsgt(struct int i915_ttm_purge(struct drm_i915_gem_object *obj) { struct ttm_buffer_object *bo = i915_gem_to_ttm(obj); - struct i915_ttm_tt *i915_tt = - container_of(bo->ttm, typeof(*i915_tt), ttm); struct ttm_operation_ctx ctx = { .interruptible = true, .no_wait_gpu = false, @@ -432,16 +430,22 @@ int i915_ttm_purge(struct drm_i915_gem_o if (ret) return ret; - if (bo->ttm && i915_tt->filp) { - /* - * The below fput(which eventually calls shmem_truncate) might - * be delayed by worker, so when directly called to purge the - * pages(like by the shrinker) we should try to be more - * aggressive and release the pages immediately. - */ - shmem_truncate_range(file_inode(i915_tt->filp), - 0, (loff_t)-1); - fput(fetch_and_zero(&i915_tt->filp)); + if (bo->ttm) { + struct i915_ttm_tt *i915_tt = + container_of(bo->ttm, typeof(*i915_tt), ttm); + + if (i915_tt->filp) { + /* + * The below fput(which eventually calls shmem_truncate) + * might be delayed by worker, so when directly called + * to purge the pages(like by the shrinker) we should + * try to be more aggressive and release the pages + * immediately. + */ + shmem_truncate_range(file_inode(i915_tt->filp), + 0, (loff_t)-1); + fput(fetch_and_zero(&i915_tt->filp)); + } } obj->write_domain = 0;