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 456AFC77B78 for ; Wed, 3 May 2023 18:21:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229708AbjECSVi (ORCPT ); Wed, 3 May 2023 14:21:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57534 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229581AbjECSVh (ORCPT ); Wed, 3 May 2023 14:21:37 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C9FDA2698 for ; Wed, 3 May 2023 11:21:36 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 7AE1D2062F; Wed, 3 May 2023 18:21:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1683138095; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=4nWShETjGYXZFdzqiA7AN/yqSqnYTxYJ+Kxc161i5cs=; b=W+H/N5AoHIvZ6U39A4C2gyWRoamW7ekVRNCSqZmJFonpSWe4on5UeJHAnGYhW6lWu9u+J8 hOfcnQw3m4l7KTmMwPheEIC8bbN5fYND+GlKrKVMjShCMYnNAn5lejUXizR3wHXNBoiUnG ERfNEPBQqTPqeSZQmJfUSG42KrZjBsw= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1683138095; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=4nWShETjGYXZFdzqiA7AN/yqSqnYTxYJ+Kxc161i5cs=; b=M7/FCQv5D5P4w1nt2uDH7GBlaNHI2UEGIrShe0PrYwCdY4/m4TEPqbAZUdGw7iLc7p+YTg dwrU5JQJBSEFftAA== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 6D93513584; Wed, 3 May 2023 18:21:35 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 2bi3Gi+mUmRFPgAAMHmgww (envelope-from ); Wed, 03 May 2023 18:21:35 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id E6E8AA0744; Wed, 3 May 2023 20:21:34 +0200 (CEST) From: Jan Kara To: Ted Tso Cc: , Dmitry Vyukov , Jan Kara , syzbot+4a03518df1e31b537066@syzkaller.appspotmail.com Subject: [PATCH] ext4: Fix data races when using cached status extents Date: Wed, 3 May 2023 20:21:28 +0200 Message-Id: <20230503182128.14115-1-jack@suse.cz> X-Mailer: git-send-email 2.35.3 MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2331; i=jack@suse.cz; h=from:subject; bh=acO5L3eFCHxd8f3y7ZiahEDMnbhguiCquKLroLErBPE=; b=owEBbQGS/pANAwAIAZydqgc/ZEDZAcsmYgBkUqYi2+MyI0UTA6/ZaHdVqI65iggxdEtqit7e+97x mO8sksmJATMEAAEIAB0WIQSrWdEr1p4yirVVKBycnaoHP2RA2QUCZFKmIgAKCRCcnaoHP2RA2XzpB/ 9iQGJR/J7vSnJWDVpf7w27aCSonwutMKGe4D5A2fgj7NdivZfK6EUbzco9yegxSJKlrgECr9XGLJZE Z/Z2M91qb9HxuVDYjl2yMpldO4qdSrL488K056ThoAaDDInG9q5dnvV11zJOlZO/e6tX5wt4za+Oaa RNwFBYzEgGvEoV6iEAYNyAetkGalEu7gbp5kAPgzuyzawoE6FcaXD6TMpJ1UOdlA7BbRbUtfGyVC6A w/mZ8diNZ5MP2gywCpCvuU6yXj7i8iV60yU9nS4bgfxNV4ZShSepSUmx0gTFBy9uBnzmlLI0RLy2Xt Bs81CSop/uigoUqRaQi7DnogmFo1Dy X-Developer-Key: i=jack@suse.cz; a=openpgp; fpr=93C6099A142276A28BBE35D815BC833443038D8C Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org When using cached extent stored in extent status tree in tree->cache_es another process holding ei->i_es_lock for reading can be racing with us setting new value of tree->cache_es. If the compiler would decide to refetch tree->cache_es at an unfortunate moment, it could result in a bogus in_range() check. Fix the possible race by using READ_ONCE() when using tree->cache_es only under ei->i_es_lock for reading. Reported-by: syzbot+4a03518df1e31b537066@syzkaller.appspotmail.com Link: https://lore.kernel.org/all/000000000000d3b33905fa0fd4a6@google.com Suggested-by: Dmitry Vyukov Signed-off-by: Jan Kara --- fs/ext4/extents_status.c | 28 ++++++++++++---------------- 1 file changed, 12 insertions(+), 16 deletions(-) diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c index 7bc221038c6c..ca2cb926894f 100644 --- a/fs/ext4/extents_status.c +++ b/fs/ext4/extents_status.c @@ -267,14 +267,12 @@ static void __es_find_extent_range(struct inode *inode, /* see if the extent has been cached */ es->es_lblk = es->es_len = es->es_pblk = 0; - if (tree->cache_es) { - es1 = tree->cache_es; - if (in_range(lblk, es1->es_lblk, es1->es_len)) { - es_debug("%u cached by [%u/%u) %llu %x\n", - lblk, es1->es_lblk, es1->es_len, - ext4_es_pblock(es1), ext4_es_status(es1)); - goto out; - } + es1 = READ_ONCE(tree->cache_es); + if (es1 && in_range(lblk, es1->es_lblk, es1->es_len)) { + es_debug("%u cached by [%u/%u) %llu %x\n", + lblk, es1->es_lblk, es1->es_len, + ext4_es_pblock(es1), ext4_es_status(es1)); + goto out; } es1 = __es_tree_search(&tree->root, lblk); @@ -931,14 +929,12 @@ int ext4_es_lookup_extent(struct inode *inode, ext4_lblk_t lblk, /* find extent in cache firstly */ es->es_lblk = es->es_len = es->es_pblk = 0; - if (tree->cache_es) { - es1 = tree->cache_es; - if (in_range(lblk, es1->es_lblk, es1->es_len)) { - es_debug("%u cached by [%u/%u)\n", - lblk, es1->es_lblk, es1->es_len); - found = 1; - goto out; - } + es1 = READ_ONCE(tree->cache_es); + if (es1 && in_range(lblk, es1->es_lblk, es1->es_len)) { + es_debug("%u cached by [%u/%u)\n", + lblk, es1->es_lblk, es1->es_len); + found = 1; + goto out; } node = tree->root.rb_node; -- 2.35.3