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 128ABC433EF for ; Wed, 1 Dec 2021 19:38:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1352772AbhLATl5 (ORCPT ); Wed, 1 Dec 2021 14:41:57 -0500 Received: from sin.source.kernel.org ([145.40.73.55]:48792 "EHLO sin.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1352783AbhLATl3 (ORCPT ); Wed, 1 Dec 2021 14:41:29 -0500 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 sin.source.kernel.org (Postfix) with ESMTPS id DC436CE20D7; Wed, 1 Dec 2021 19:38:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DE066C53FD2; Wed, 1 Dec 2021 19:38:02 +0000 (UTC) From: Catalin Marinas To: Linus Torvalds , Andreas Gruenbacher Cc: Josef Bacik , David Sterba , Al Viro , Andrew Morton , Will Deacon , Matthew Wilcox , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-btrfs@vger.kernel.org Subject: [PATCH v2 4/4] btrfs: Avoid live-lock in search_ioctl() on hardware with sub-page faults Date: Wed, 1 Dec 2021 19:37:50 +0000 Message-Id: <20211201193750.2097885-5-catalin.marinas@arm.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20211201193750.2097885-1-catalin.marinas@arm.com> References: <20211201193750.2097885-1-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. Request a 'min_size' of (*buf_size - sk_offset) from fault_in_writeable() to check this range for sub-page faults. Fixes: a48b73eca4ce ("btrfs: fix potential deadlock in the search ioctl") Signed-off-by: Catalin Marinas Reported-by: Al Viro --- 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 c7d74c8776a1..439cf38f320a 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -2222,8 +2222,13 @@ 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, 0)) + /* + * Ensure that the whole user buffer is faulted in at sub-page + * granularity, otherwise the loop may live-lock. + */ + if (fault_in_writeable(ubuf + sk_offset, len, len)) break; ret = btrfs_search_forward(root, &key, path, sk->min_transid);