From patchwork Fri Oct 8 09:50:07 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Tvrtko Ursulin X-Patchwork-Id: 12544827 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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 11DBAC433EF for ; Fri, 8 Oct 2021 09:50:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F1375600D4 for ; Fri, 8 Oct 2021 09:50:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236118AbhJHJwP (ORCPT ); Fri, 8 Oct 2021 05:52:15 -0400 Received: from mga01.intel.com ([192.55.52.88]:33869 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229869AbhJHJwO (ORCPT ); Fri, 8 Oct 2021 05:52:14 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10130"; a="249834350" X-IronPort-AV: E=Sophos;i="5.85,357,1624345200"; d="scan'208";a="249834350" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Oct 2021 02:50:18 -0700 X-IronPort-AV: E=Sophos;i="5.85,357,1624345200"; d="scan'208";a="478920486" Received: from tocallag-mobl2.ger.corp.intel.com (HELO tursulin-mobl2.home) ([10.213.250.80]) by orsmga007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Oct 2021 02:50:16 -0700 From: Tvrtko Ursulin To: Intel-gfx@lists.freedesktop.org Cc: dri-devel@lists.freedesktop.org, Tvrtko Ursulin , =?utf-8?q?Christian_K=C3=B6nig?= , Daniel Vetter , Sumit Semwal , linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org Subject: [PATCH] dma-resv: Fix dma_resv_get_fences and dma_resv_copy_fences after conversion Date: Fri, 8 Oct 2021 10:50:07 +0100 Message-Id: <20211008095007.972693-1-tvrtko.ursulin@linux.intel.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org From: Tvrtko Ursulin Cache the count of shared fences in the iterator to avoid dereferencing the dma_resv_object outside the RCU protection. Otherwise iterator and its users can observe an incosistent state which makes it impossible to use safely. Such as: <6> [187.517041] [IGT] gem_sync: executing <7> [187.536343] i915 0000:00:02.0: [drm:i915_gem_context_create_ioctl [i915]] HW context 1 created <7> [187.536793] i915 0000:00:02.0: [drm:i915_gem_context_create_ioctl [i915]] HW context 1 created <6> [187.551235] [IGT] gem_sync: starting subtest basic-many-each <1> [188.935462] BUG: kernel NULL pointer dereference, address: 0000000000000010 <1> [188.935485] #PF: supervisor write access in kernel mode <1> [188.935495] #PF: error_code(0x0002) - not-present page <6> [188.935504] PGD 0 P4D 0 <4> [188.935512] Oops: 0002 [#1] PREEMPT SMP NOPTI <4> [188.935521] CPU: 2 PID: 1467 Comm: gem_sync Not tainted 5.15.0-rc4-CI-Patchwork_21264+ #1 <4> [188.935535] Hardware name: /NUC6CAYB, BIOS AYAPLCEL.86A.0049.2018.0508.1356 05/08/2018 <4> [188.935546] RIP: 0010:dma_resv_get_fences+0x116/0x2d0 <4> [188.935560] Code: 10 85 c0 7f c9 be 03 00 00 00 e8 15 8b df ff eb bd e8 8e c6 ff ff eb b6 41 8b 04 24 49 8b 55 00 48 89 e7 8d 48 01 41 89 0c 24 <4c> 89 34 c2 e8 41 f2 ff ff 49 89 c6 48 85 c0 75 8c 48 8b 44 24 10 <4> [188.935583] RSP: 0018:ffffc900011dbcc8 EFLAGS: 00010202 <4> [188.935593] RAX: 0000000000000000 RBX: 00000000ffffffff RCX: 0000000000000001 <4> [188.935603] RDX: 0000000000000010 RSI: ffffffff822e343c RDI: ffffc900011dbcc8 <4> [188.935613] RBP: ffffc900011dbd48 R08: ffff88812d255bb8 R09: 00000000fffffffe <4> [188.935623] R10: 0000000000000001 R11: 0000000000000000 R12: ffffc900011dbd44 <4> [188.935633] R13: ffffc900011dbd50 R14: ffff888113d29cc0 R15: 0000000000000000 <4> [188.935643] FS: 00007f68d17e9700(0000) GS:ffff888277900000(0000) knlGS:0000000000000000 <4> [188.935655] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 <4> [188.935665] CR2: 0000000000000010 CR3: 000000012d0a4000 CR4: 00000000003506e0 <4> [188.935676] Call Trace: <4> [188.935685] i915_gem_object_wait+0x1ff/0x410 [i915] <4> [188.935988] i915_gem_wait_ioctl+0xf2/0x2a0 [i915] <4> [188.936272] ? i915_gem_object_wait+0x410/0x410 [i915] <4> [188.936533] drm_ioctl_kernel+0xae/0x140 <4> [188.936546] drm_ioctl+0x201/0x3d0 <4> [188.936555] ? i915_gem_object_wait+0x410/0x410 [i915] <4> [188.936820] ? __fget_files+0xc2/0x1c0 <4> [188.936830] ? __fget_files+0xda/0x1c0 <4> [188.936839] __x64_sys_ioctl+0x6d/0xa0 <4> [188.936848] do_syscall_64+0x3a/0xb0 <4> [188.936859] entry_SYSCALL_64_after_hwframe+0x44/0xae If the shared object has changed during the RCU unlocked period callers will correctly handle the restart on the next iteration. Signed-off-by: Tvrtko Ursulin Fixes: 96601e8a4755 ("dma-buf: use new iterator in dma_resv_copy_fences") Fixes: d3c80698c9f5 ("dma-buf: use new iterator in dma_resv_get_fences v3") Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/4274 Cc: Christian König Cc: Daniel Vetter Cc: Sumit Semwal Cc: linux-media@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Cc: linaro-mm-sig@lists.linaro.org --- drivers/dma-buf/dma-resv.c | 18 ++++++++++-------- include/linux/dma-resv.h | 5 ++++- 2 files changed, 14 insertions(+), 9 deletions(-) diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c index a480af9581bd..7b6d881c8904 100644 --- a/drivers/dma-buf/dma-resv.c +++ b/drivers/dma-buf/dma-resv.c @@ -333,10 +333,14 @@ static void dma_resv_iter_restart_unlocked(struct dma_resv_iter *cursor) { cursor->seq = read_seqcount_begin(&cursor->obj->seq); cursor->index = -1; - if (cursor->all_fences) + cursor->shared_count = 0; + if (cursor->all_fences) { cursor->fences = dma_resv_shared_list(cursor->obj); - else + if (cursor->fences) + cursor->shared_count = cursor->fences->shared_count; + } else { cursor->fences = NULL; + } cursor->is_restarted = true; } @@ -363,7 +367,7 @@ static void dma_resv_iter_walk_unlocked(struct dma_resv_iter *cursor) continue; } else if (!cursor->fences || - cursor->index >= cursor->fences->shared_count) { + cursor->index >= cursor->shared_count) { cursor->fence = NULL; break; @@ -448,10 +452,8 @@ int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src) dma_resv_list_free(list); dma_fence_put(excl); - if (cursor.fences) { - unsigned int cnt = cursor.fences->shared_count; - - list = dma_resv_list_alloc(cnt); + if (cursor.shared_count) { + list = dma_resv_list_alloc(cursor.shared_count); if (!list) { dma_resv_iter_end(&cursor); return -ENOMEM; @@ -522,7 +524,7 @@ int dma_resv_get_fences(struct dma_resv *obj, struct dma_fence **fence_excl, if (fence_excl) dma_fence_put(*fence_excl); - count = cursor.fences ? cursor.fences->shared_count : 0; + count = cursor.shared_count; count += fence_excl ? 0 : 1; /* Eventually re-allocate the array */ diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h index 8b6c20636a79..3e1bff147428 100644 --- a/include/linux/dma-resv.h +++ b/include/linux/dma-resv.h @@ -170,9 +170,12 @@ struct dma_resv_iter { /** @index: index into the shared fences */ unsigned int index; - /** @fences: the shared fences */ + /** @fences: the shared fences; private, *MUST* not dereference */ struct dma_resv_list *fences; + /** @shared_count: number of shared fences */ + unsigned int shared_count; + /** @is_restarted: true if this is the first returned fence */ bool is_restarted; };