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 644C1C433EF for ; Wed, 6 Apr 2022 20:15:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232258AbiDFURI (ORCPT ); Wed, 6 Apr 2022 16:17:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43578 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234336AbiDFUQZ (ORCPT ); Wed, 6 Apr 2022 16:16:25 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CB472264C2E; Wed, 6 Apr 2022 11:09:36 -0700 (PDT) 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 4ADF861BD1; Wed, 6 Apr 2022 18:09:36 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4F5EEC385A5; Wed, 6 Apr 2022 18:09:33 +0000 (UTC) From: Catalin Marinas To: Linus Torvalds , Andreas Gruenbacher , Josef Bacik Cc: Al Viro , Andrew Morton , Chris Mason , David Sterba , Will Deacon , linux-fsdevel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v3 3/3] btrfs: Avoid live-lock in search_ioctl() on hardware with sub-page faults Date: Wed, 6 Apr 2022 19:09:22 +0100 Message-Id: <20220406180922.1522433-4-catalin.marinas@arm.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220406180922.1522433-1-catalin.marinas@arm.com> References: <20220406180922.1522433-1-catalin.marinas@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit a48b73eca4ce ("btrfs: fix potential deadlock in the search ioctl") addressed a lockdep warning by pre-faulting the user pages and attempting the copy_to_user_nofault() in an infinite loop. On architectures like arm64 with MTE, an access may fault within a page at a location different from what fault_in_writeable() probed. Since the sk_offset is rewound to the previous struct btrfs_ioctl_search_header boundary, there is no guaranteed forward progress and search_ioctl() may live-lock. Use fault_in_subpage_writeable() instead of fault_in_writeable() to ensure the permission is checked at the right granularity (smaller than PAGE_SIZE). Signed-off-by: Catalin Marinas Fixes: a48b73eca4ce ("btrfs: fix potential deadlock in the search ioctl") Reported-by: Al Viro Cc: Chris Mason Cc: Josef Bacik Cc: David Sterba --- fs/btrfs/ioctl.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index 238cee5b5254..d49e8254f823 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -2556,8 +2556,13 @@ static noinline int search_ioctl(struct inode *inode, key.offset = sk->min_offset; while (1) { + size_t len = *buf_size - sk_offset; ret = -EFAULT; - if (fault_in_writeable(ubuf + sk_offset, *buf_size - sk_offset)) + /* + * Ensure that the whole user buffer is faulted in at sub-page + * granularity, otherwise the loop may live-lock. + */ + if (fault_in_subpage_writeable(ubuf + sk_offset, len)) break; ret = btrfs_search_forward(root, &key, path, sk->min_transid);