6.12-stable review patch. If anyone has any objections, please let me know.
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From: OGAWA Hirofumi hirofumi@mail.parknet.co.jp
[ Upstream commit b49125574cae26458d4aa02ce8f4523ba9a2a328 ]
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@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=a5d8c609c02f508672cc Reviewed-by: Ming Lei ming.lei@redhat.com Signed-off-by: OGAWA Hirofumi hirofumi@mail.parknet.co.jp Signed-off-by: Jens Axboe axboe@kernel.dk Stable-dep-of: f5c84eff634b ("loop: Add sanity check for read/write_iter") Signed-off-by: Sasha Levin sashal@kernel.org --- 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 1f55ddef53f3d..27e4bd8ee9dc9 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -694,12 +694,11 @@ static void loop_sysfs_exit(struct loop_device *lo) &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;
/* @@ -712,24 +711,17 @@ static void loop_config_discard(struct loop_device *lo, 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 { @@ -915,6 +907,7 @@ static int loop_reconfigure_limits(struct loop_device *lo, unsigned int bsize) 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); @@ -924,6 +917,8 @@ static int loop_reconfigure_limits(struct loop_device *lo, unsigned int bsize) 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; @@ -933,7 +928,12 @@ static int loop_reconfigure_limits(struct loop_device *lo, unsigned int bsize) 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); }