From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.parknet.co.jp (mail.parknet.co.jp [210.171.160.6]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 10D771A3A80; Mon, 11 Nov 2024 16:43:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=210.171.160.6 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731343438; cv=none; b=NfpL9ejVcjvQ2Maptd6suCJOedIkc8DtXAoSVv62+ok86SmE3ZbMNuaSFpGPY40Q+8MxcYTGSJ0IcwzIegW+FgsrogrBmzjJ8pRfvUN3KByzsg+8uNv6QlTk7yAdWvA4mWK0JBAvixN+KQAZq+1GDi/z7Aif2c0QAfiOFAAjO7k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731343438; c=relaxed/simple; bh=nknNO/X4QZPpB3akptkMCCcdCYltGPKsxIrYle5JUFI=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=TLSwFpZyqMrGCZPLY6E2ah7usjCwZbVlktJtZmN4qUvDqvGn+YMkBpRfyPtMgkuHA8EirYBvEakJ0GI6iDCCFsFJg3hJE2+KRqhELkY/1h69VNC3wqYVGxYe2xFIApZM2mhG+iKF3ofGifFdq+uhJ8FElwXHEXAaERHsskQ80C4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=mail.parknet.co.jp; spf=pass smtp.mailfrom=parknet.co.jp; arc=none smtp.client-ip=210.171.160.6 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=mail.parknet.co.jp Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=parknet.co.jp Received: from ibmpc.myhome.or.jp (server.parknet.ne.jp [210.171.168.39]) by mail.parknet.co.jp (Postfix) with ESMTPSA id 5FFDA284C597; Mon, 11 Nov 2024 22:07:24 +0900 (JST) Received: from devron.myhome.or.jp (foobar@devron.myhome.or.jp [192.168.0.3]) by ibmpc.myhome.or.jp (8.18.1/8.18.1/Debian-6) with ESMTPS id 4ABD7NTb073975 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Mon, 11 Nov 2024 22:07:24 +0900 Received: from devron.myhome.or.jp (foobar@localhost [127.0.0.1]) by devron.myhome.or.jp (8.18.1/8.18.1/Debian-6) with ESMTPS id 4ABD7NOK740352 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Mon, 11 Nov 2024 22:07:23 +0900 Received: (from hirofumi@localhost) by devron.myhome.or.jp (8.18.1/8.18.1/Submit) id 4ABD7Lwo740344; Mon, 11 Nov 2024 22:07:21 +0900 From: OGAWA Hirofumi To: Jens Axboe Cc: linux-block@vger.kernel.org, syzbot , linkinjeon@kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, sj1557.seo@samsung.com, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [exfat?] possible deadlock in fat_count_free_clusters In-Reply-To: <67313d9e.050a0220.138bd5.0054.GAE@google.com> (syzbot's message of "Sun, 10 Nov 2024 15:11:26 -0800") References: <67313d9e.050a0220.138bd5.0054.GAE@google.com> Date: Mon, 11 Nov 2024 22:07:21 +0900 Message-ID: <8734jxsyuu.fsf@mail.parknet.co.jp> User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain Hi, syzbot writes: > syzbot found the following issue on: > > HEAD commit: 929beafbe7ac Add linux-next specific files for 20241108 > git tree: linux-next > console output: https://syzkaller.appspot.com/x/log.txt?x=1621bd87980000 > kernel config: https://syzkaller.appspot.com/x/.config?x=75175323f2078363 > dashboard link: https://syzkaller.appspot.com/bug?extid=a5d8c609c02f508672cc > compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 This patch is to fix the above race. Please check this. Thanks From: OGAWA Hirofumi Subject: [PATCH] loop: Fix ABBA locking race Date: Mon, 11 Nov 2024 21:53:36 +0900 Current loop calls vfs_statfs() while holding the q->limits_lock. If FS takes some locking in vfs_statfs callback, this may lead to ABBA locking bug (at least, FAT fs has this issue actually). So this patch calls vfs_statfs() outside q->limits_locks instead, because looks like there is no reason to hold q->limits_locks while getting discard configs. Chain exists of: &sbi->fat_lock --> &q->q_usage_counter(io)#17 --> &q->limits_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->limits_lock); lock(&q->q_usage_counter(io)#17); lock(&q->limits_lock); lock(&sbi->fat_lock); *** DEADLOCK *** Reported-by: syzbot+a5d8c609c02f508672cc@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=a5d8c609c02f508672cc Signed-off-by: OGAWA Hirofumi --- drivers/block/loop.c | 31 ++++++++++++++++--------------- 1 file changed, 16 insertions(+), 15 deletions(-) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 78a7bb2..5f3ce51 100644 --- a/drivers/block/loop.c 2024-09-16 13:45:20.253220178 +0900 +++ b/drivers/block/loop.c 2024-11-11 21:51:00.910135443 +0900 @@ -770,12 +770,11 @@ static void loop_sysfs_exit(struct loop_ &loop_attribute_group); } -static void loop_config_discard(struct loop_device *lo, - struct queue_limits *lim) +static void loop_get_discard_config(struct loop_device *lo, + u32 *granularity, u32 *max_discard_sectors) { struct file *file = lo->lo_backing_file; struct inode *inode = file->f_mapping->host; - u32 granularity = 0, max_discard_sectors = 0; struct kstatfs sbuf; /* @@ -788,8 +787,9 @@ static void loop_config_discard(struct l if (S_ISBLK(inode->i_mode)) { struct request_queue *backingq = bdev_get_queue(I_BDEV(inode)); - max_discard_sectors = backingq->limits.max_write_zeroes_sectors; - granularity = bdev_discard_granularity(I_BDEV(inode)) ?: + *max_discard_sectors = + backingq->limits.max_write_zeroes_sectors; + *granularity = bdev_discard_granularity(I_BDEV(inode)) ?: queue_physical_block_size(backingq); /* @@ -797,16 +797,9 @@ static void loop_config_discard(struct l * image a.k.a. discard. */ } else if (file->f_op->fallocate && !vfs_statfs(&file->f_path, &sbuf)) { - max_discard_sectors = UINT_MAX >> 9; - granularity = sbuf.f_bsize; + *max_discard_sectors = UINT_MAX >> 9; + *granularity = sbuf.f_bsize; } - - lim->max_hw_discard_sectors = max_discard_sectors; - lim->max_write_zeroes_sectors = max_discard_sectors; - if (max_discard_sectors) - lim->discard_granularity = granularity; - else - lim->discard_granularity = 0; } struct loop_worker { @@ -992,6 +985,7 @@ static int loop_reconfigure_limits(struc struct inode *inode = file->f_mapping->host; struct block_device *backing_bdev = NULL; struct queue_limits lim; + u32 granularity = 0, max_discard_sectors = 0; if (S_ISBLK(inode->i_mode)) backing_bdev = I_BDEV(inode); @@ -1001,6 +995,8 @@ static int loop_reconfigure_limits(struc if (!bsize) bsize = loop_default_blocksize(lo, backing_bdev); + loop_get_discard_config(lo, &granularity, &max_discard_sectors); + lim = queue_limits_start_update(lo->lo_queue); lim.logical_block_size = bsize; lim.physical_block_size = bsize; @@ -1010,7 +1006,12 @@ static int loop_reconfigure_limits(struc lim.features |= BLK_FEAT_WRITE_CACHE; if (backing_bdev && !bdev_nonrot(backing_bdev)) lim.features |= BLK_FEAT_ROTATIONAL; - loop_config_discard(lo, &lim); + lim.max_hw_discard_sectors = max_discard_sectors; + lim.max_write_zeroes_sectors = max_discard_sectors; + if (max_discard_sectors) + lim.discard_granularity = granularity; + else + lim.discard_granularity = 0; return queue_limits_commit_update(lo->lo_queue, &lim); } _ -- OGAWA Hirofumi