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[2620:137:e000::1:20]) by mx.google.com with ESMTP id 3-20020a170906328300b007827639faffsi1451697ejw.760.2022.11.30.11.14.46; Wed, 30 Nov 2022 11:15:11 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20210112 header.b=WGTJiF3y; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230352AbiK3S6J (ORCPT + 99 others); Wed, 30 Nov 2022 13:58:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48722 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230247AbiK3S6C (ORCPT ); Wed, 30 Nov 2022 13:58:02 -0500 Received: from mail-pg1-x530.google.com (mail-pg1-x530.google.com [IPv6:2607:f8b0:4864:20::530]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CE5A94A5A2; Wed, 30 Nov 2022 10:57:58 -0800 (PST) Received: by mail-pg1-x530.google.com with SMTP id 82so9458484pgc.0; Wed, 30 Nov 2022 10:57:58 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=HARMmg9a8K/b5vAg5+2jWHn5nGF+ldiYt0bz7xqmdnE=; b=WGTJiF3yAhGqZTID6d08gJEXQ4pOpw/F8IW70Fk4DX3/XKK4GX6O6O5z6sEg6z3ZxA nKoCubP1Y5g7MDxpafjnlDV+EId4HA5w7daSh2YvcN6HdV0obI9+UFlyKjmkKYqFR72y gMWy1dzzql8GfeFzdH/WmENL31+zec2xHdtXcCkYXTjR8m3n4QiPg3PrzBzgOcwPIHS6 AaR7qidp6vLsXCgkZT4up/CQ2btS/YTKnCNO3QAxE+f6yYpnKWixbNMgPaXlio5w8zOX hxUDE2u3oizkjBG0c3nPpcxfw2PyzrMLfX65HIkSY8twjcXL4M+p+vy8Z5yNr+rm4yNn JTgA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=HARMmg9a8K/b5vAg5+2jWHn5nGF+ldiYt0bz7xqmdnE=; b=qxgeTRD4kqFhqcCAYiK5nZTLG09+JX8DxDIex1JvgbVZTzcf3EBKgEaVzTOWfq8h4D NsdfoqJ3Jxrn2+LP03ljDUlMEQVWls3lzGbJ76S8vxcmEbVMIIz41acfgEtvOhQ5kwfT 9eLW/+OCQ1i+D0ZlHYNKNADaSr5cq99kIbl/bbVwix88jgzDoppVx4GrCxN+8cobZMwN ujounUfO0wtjY6Xr3pgnBqEZbHsW7YOz717n3EOy3ogHub8TAiNfYOWabhnwwuKR08z3 /XRXgijgjtpVcicSiRx1UFZMCQNiHm8LuZx6KracT+f+rp6VmWSu+tWmSVMZzKMVrwYw W3EQ== X-Gm-Message-State: ANoB5pnTaMuLH63HbNuWao7cpnuF2Uyy8OBWU8VgWxDzyxa/6Wf2/AF/ YjNZ+XrEweP0zQjc95bpGFY= X-Received: by 2002:a63:f506:0:b0:470:14fa:a294 with SMTP id w6-20020a63f506000000b0047014faa294mr37579508pgh.361.1669834678336; Wed, 30 Nov 2022 10:57:58 -0800 (PST) Received: from localhost ([2a00:79e1:abd:4a00:2703:3c72:eb1a:cffd]) by smtp.gmail.com with ESMTPSA id q14-20020aa7842e000000b00575cc2f74ffsm1735664pfn.35.2022.11.30.10.57.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Nov 2022 10:57:57 -0800 (PST) From: Rob Clark To: dri-devel@lists.freedesktop.org Cc: Daniel Vetter , Rob Clark , stable@vger.kernel.org, Daniel Vetter , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Eric Anholt , =?utf-8?q?Noralf_Tr=C3=B8nnes?= , Rob Herring , linux-kernel@vger.kernel.org (open list) Subject: [PATCH v2 2/2] drm/shmem-helper: Avoid vm_open error paths Date: Wed, 30 Nov 2022 10:57:48 -0800 Message-Id: <20221130185748.357410-3-robdclark@gmail.com> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221130185748.357410-1-robdclark@gmail.com> References: <20221130185748.357410-1-robdclark@gmail.com> MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM, RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1750949651245977381?= X-GMAIL-MSGID: =?utf-8?q?1750949651245977381?= From: Rob Clark vm_open() is not allowed to fail. Fortunately we are guaranteed that the pages are already pinned, thanks to the initial mmap which is now being cloned into a forked process, and only need to increment the refcnt. So just increment it directly. Previously if a signal was delivered at the wrong time to the forking process, the mutex_lock_interruptible() could fail resulting in the pages_use_count not being incremented. Fixes: 2194a63a818d ("drm: Add library for shmem backed GEM objects") Cc: stable@vger.kernel.org Signed-off-by: Rob Clark Reviewed-by: Daniel Vetter --- drivers/gpu/drm/drm_gem_shmem_helper.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c index 3b7b71391a4c..b602cd72a120 100644 --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -571,12 +571,20 @@ static void drm_gem_shmem_vm_open(struct vm_area_struct *vma) { struct drm_gem_object *obj = vma->vm_private_data; struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj); - int ret; WARN_ON(shmem->base.import_attach); - ret = drm_gem_shmem_get_pages(shmem); - WARN_ON_ONCE(ret != 0); + mutex_lock(&shmem->pages_lock); + + /* + * We should have already pinned the pages when the buffer was first + * mmap'd, vm_open() just grabs an additional reference for the new + * mm the vma is getting copied into (ie. on fork()). + */ + if (!WARN_ON_ONCE(!shmem->pages_use_count)) + shmem->pages_use_count++; + + mutex_unlock(&shmem->pages_lock); drm_gem_vm_open(vma); }