Jens Axboe <axboe@xxxxxxxxx> writes: > On 11/19/24 5:10 AM, Ming Lei wrote: >> On Tue, Nov 12, 2024 at 12:44 AM OGAWA Hirofumi >> <hirofumi@xxxxxxxxxxxxxxxxxx> wrote: >>> >>> Hi, >>> >>> syzbot <syzbot+a5d8c609c02f508672cc@xxxxxxxxxxxxxxxxxxxxxxxxx> 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 [...] >> >> Looks fine, >> >> Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx> > > The patch doesn't apply to the for-6.13/block tree, Ogawa can you send > an updated one please? Updated the patch for linux-block:for-6.13/block. Please apply. Thanks. From: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx> Subject: [PATCH] loop: Fix ABBA locking race Date: Tue, 19 Nov 2024 23:42:23 +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 no reason to hold q->limits_locks while getting discord 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@xxxxxxxxxxxxxxxxxxxxxxxxx Closes: https://syzkaller.appspot.com/bug?extid=a5d8c609c02f508672cc Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx> Signed-off-by: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx> --- drivers/block/loop.c | 30 +++++++++++++++--------------- 1 file changed, 15 insertions(+), 15 deletions(-) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index fe9bb4f..8f6761c 100644 --- a/drivers/block/loop.c 2024-11-19 23:37:54.760751014 +0900 +++ b/drivers/block/loop.c 2024-11-19 23:38:55.645461107 +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; /* @@ -788,24 +787,17 @@ static void loop_config_discard(struct l if (S_ISBLK(inode->i_mode)) { struct block_device *bdev = I_BDEV(inode); - max_discard_sectors = bdev_write_zeroes_sectors(bdev); - granularity = bdev_discard_granularity(bdev); + *max_discard_sectors = bdev_write_zeroes_sectors(bdev); + *granularity = bdev_discard_granularity(bdev); /* * We use punch hole to reclaim the free space used by the * 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 { @@ -991,6 +983,7 @@ 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); @@ -1000,6 +993,8 @@ 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; @@ -1009,7 +1004,12 @@ 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 <hirofumi@xxxxxxxxxxxxxxxxxx>
