From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161460AbcFMSiB (ORCPT ); Mon, 13 Jun 2016 14:38:01 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:43505 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161392AbcFMShd (ORCPT ); Mon, 13 Jun 2016 14:37:33 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Chris Wilson" , "Tvrtko Ursulin" , "Jani Nikula" , "=?UTF-8?Q?Micha=C5=82=20?=Winiarski" Date: Mon, 13 Jun 2016 19:36:37 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 032/114] drm/i915/userptr: Hold mmref whilst calling get-user-pages In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.36-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Chris Wilson commit db9f9203e27495b2d151b695504e286eec026e9b upstream. Holding a reference to the containing task_struct is not sufficient to prevent the mm_struct from being reaped under memory pressure. If this happens whilst we are calling get_user_pages(), explosions erupt - sometimes an immediate GPF, sometimes page flag corruption. To prevent the target mm from being reaped as we are reading from it, acquire a reference before we begin. Testcase: igt/gem_shrink/*userptr Signed-off-by: Chris Wilson Cc: Tvrtko Ursulin Cc: Michał Winiarski Reviewed-by: Michał Winiarski Link: http://patchwork.freedesktop.org/patch/msgid/1459864801-28606-2-git-send-email-chris@chris-wilson.co.uk (cherry picked from commit 40313f0cd0b711a7a5905e5182422799e157d8aa) Signed-off-by: Jani Nikula [bwh: Backported to 3.16: - s/get_user_pages_remote/get_user_pages/ - s/npages/num_pages/] Signed-off-by: Ben Hutchings --- drivers/gpu/drm/i915/i915_gem_userptr.c | 29 +++++++++++++++++------------ 1 file changed, 17 insertions(+), 12 deletions(-) --- a/drivers/gpu/drm/i915/i915_gem_userptr.c +++ b/drivers/gpu/drm/i915/i915_gem_userptr.c @@ -411,19 +411,24 @@ __i915_gem_userptr_get_pages_worker(stru if (pvec != NULL) { struct mm_struct *mm = obj->userptr.mm; - down_read(&mm->mmap_sem); - while (pinned < num_pages) { - ret = get_user_pages(work->task, mm, - obj->userptr.ptr + pinned * PAGE_SIZE, - num_pages - pinned, - !obj->userptr.read_only, 0, - pvec + pinned, NULL); - if (ret < 0) - break; + ret = -EFAULT; + if (atomic_inc_not_zero(&mm->mm_users)) { + down_read(&mm->mmap_sem); + while (pinned < num_pages) { + ret = get_user_pages + (work->task, mm, + obj->userptr.ptr + pinned * PAGE_SIZE, + num_pages - pinned, + !obj->userptr.read_only, 0, + pvec + pinned, NULL); + if (ret < 0) + break; - pinned += ret; + pinned += ret; + } + up_read(&mm->mmap_sem); + mmput(mm); } - up_read(&mm->mmap_sem); } mutex_lock(&dev->struct_mutex);