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 X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C34C4C352A3 for ; Mon, 10 Feb 2020 12:45:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9865F2051A for ; Mon, 10 Feb 2020 12:45:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581338706; bh=b4HgXi/kmF73E2ta0DmMNsR3/6Ln/Jv6457b+UhrBsk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=dtUiP1fVUzZSH2sC5jWQEA2N0BeruzJrPQUs4CSIabiBWVr29Vd/Fy1ZItSWSZDAx X5DekNsIAZBVZlZJ8zu4lg/Jok7TwDKZo0BKQCZOylmrxKpQJbSZf1XLvwHD/Gebwq wMVzv97cU/LJuIr4IIzxLjsNpOpo8EyUmRTcbZJk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730763AbgBJMpF (ORCPT ); Mon, 10 Feb 2020 07:45:05 -0500 Received: from mail.kernel.org ([198.145.29.99]:41692 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729804AbgBJMku (ORCPT ); Mon, 10 Feb 2020 07:40:50 -0500 Received: from localhost (unknown [209.37.97.194]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 35BBB20733; Mon, 10 Feb 2020 12:40:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581338449; bh=b4HgXi/kmF73E2ta0DmMNsR3/6Ln/Jv6457b+UhrBsk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Y32/7GSi4Svb86tndctvyPFzhqj7b2pD78da6f1xZoinsKZmxDd0MHBUSEUOAX1BH SUuadg14DpLM2QjGuboV52EgZjXt9JLMdEVR6h+VT5FwRjT2Ed3GVT950elFV3Qq4v x3/nosTzQyrqwaOBnPPMHDLa3EgmmEnZmgUhdrtI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Biggers , Theodore Tso Subject: [PATCH 5.5 193/367] ext4: fix deadlock allocating crypto bounce page from mempool Date: Mon, 10 Feb 2020 04:31:46 -0800 Message-Id: <20200210122442.412464697@linuxfoundation.org> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200210122423.695146547@linuxfoundation.org> References: <20200210122423.695146547@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Eric Biggers commit 547c556f4db7c09447ecf5f833ab6aaae0c5ab58 upstream. ext4_writepages() on an encrypted file has to encrypt the data, but it can't modify the pagecache pages in-place, so it encrypts the data into bounce pages and writes those instead. All bounce pages are allocated from a mempool using GFP_NOFS. This is not correct use of a mempool, and it can deadlock. This is because GFP_NOFS includes __GFP_DIRECT_RECLAIM, which enables the "never fail" mode for mempool_alloc() where a failed allocation will fall back to waiting for one of the preallocated elements in the pool. But since this mode is used for all a bio's pages and not just the first, it can deadlock waiting for pages already in the bio to be freed. This deadlock can be reproduced by patching mempool_alloc() to pretend that pool->alloc() always fails (so that it always falls back to the preallocations), and then creating an encrypted file of size > 128 KiB. Fix it by only using GFP_NOFS for the first page in the bio. For subsequent pages just use GFP_NOWAIT, and if any of those fail, just submit the bio and start a new one. This will need to be fixed in f2fs too, but that's less straightforward. Fixes: c9af28fdd449 ("ext4 crypto: don't let data integrity writebacks fail with ENOMEM") Cc: stable@vger.kernel.org Signed-off-by: Eric Biggers Link: https://lore.kernel.org/r/20191231181149.47619-1-ebiggers@kernel.org Signed-off-by: Theodore Ts'o Signed-off-by: Greg Kroah-Hartman --- fs/ext4/page-io.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) --- a/fs/ext4/page-io.c +++ b/fs/ext4/page-io.c @@ -512,17 +512,26 @@ int ext4_bio_write_page(struct ext4_io_s gfp_t gfp_flags = GFP_NOFS; unsigned int enc_bytes = round_up(len, i_blocksize(inode)); + /* + * Since bounce page allocation uses a mempool, we can only use + * a waiting mask (i.e. request guaranteed allocation) on the + * first page of the bio. Otherwise it can deadlock. + */ + if (io->io_bio) + gfp_flags = GFP_NOWAIT | __GFP_NOWARN; retry_encrypt: bounce_page = fscrypt_encrypt_pagecache_blocks(page, enc_bytes, 0, gfp_flags); if (IS_ERR(bounce_page)) { ret = PTR_ERR(bounce_page); - if (ret == -ENOMEM && wbc->sync_mode == WB_SYNC_ALL) { - if (io->io_bio) { + if (ret == -ENOMEM && + (io->io_bio || wbc->sync_mode == WB_SYNC_ALL)) { + gfp_flags = GFP_NOFS; + if (io->io_bio) ext4_io_submit(io); - congestion_wait(BLK_RW_ASYNC, HZ/50); - } - gfp_flags |= __GFP_NOFAIL; + else + gfp_flags |= __GFP_NOFAIL; + congestion_wait(BLK_RW_ASYNC, HZ/50); goto retry_encrypt; }