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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 06960C4167B for ; Mon, 12 Dec 2022 13:28:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232432AbiLLN2p (ORCPT ); Mon, 12 Dec 2022 08:28:45 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56516 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232493AbiLLN2Z (ORCPT ); Mon, 12 Dec 2022 08:28:25 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DCC785FAB for ; Mon, 12 Dec 2022 05:28:23 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 78E6660FF4 for ; Mon, 12 Dec 2022 13:28:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2EC9CC433D2; Mon, 12 Dec 2022 13:28:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1670851702; bh=FWD5lyEC3nGhZHhzYOluEBmtHeupPeDRZ/vk9A1MoIo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zIOumGo2f6VkzB3ecZr1zh8bD+xHrAM5MixwJVXkT4PdiGQUfj4k/GfBwXeTB61DL UaLGOpimTzS759sB+GVVDM3vTQ7zYcM63kujz1NGSDrMWOW+NaNFW+iY5XnetX4dB/ 9rQUIarQC6c0mpkCTGJx2u6/d50OZO5trgMm6cdg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Rob Clark , Daniel Vetter , Javier Martinez Canillas Subject: [PATCH 5.15 052/123] drm/shmem-helper: Avoid vm_open error paths Date: Mon, 12 Dec 2022 14:16:58 +0100 Message-Id: <20221212130929.112550463@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221212130926.811961601@linuxfoundation.org> References: <20221212130926.811961601@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Rob Clark commit 09bf649a74573cb596e211418a4f8008f265c5a9 upstream. 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 Signed-off-by: Javier Martinez Canillas Link: https://patchwork.freedesktop.org/patch/msgid/20221130185748.357410-3-robdclark@gmail.com Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/drm_gem_shmem_helper.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -541,12 +541,20 @@ static void drm_gem_shmem_vm_open(struct { 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); }