4.20-stable review patch. If anyone has any objections, please let me know.
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From: Jan Kara jack@suse.cz
commit 04906b2f542c23626b0ef6219b808406f8dddbe9 upstream.
bd_set_size() updates also block device's block size. This is somewhat unexpected from its name and at this point, only blkdev_open() uses this functionality. Furthermore, this can result in changing block size under a filesystem mounted on a loop device which leads to livelocks inside __getblk_gfp() like:
Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 PID: 10863 Comm: syz-executor0 Not tainted 4.18.0-rc5+ #151 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:__sanitizer_cov_trace_pc+0x3f/0x50 kernel/kcov.c:106 ... Call Trace: init_page_buffers+0x3e2/0x530 fs/buffer.c:904 grow_dev_page fs/buffer.c:947 [inline] grow_buffers fs/buffer.c:1009 [inline] __getblk_slow fs/buffer.c:1036 [inline] __getblk_gfp+0x906/0xb10 fs/buffer.c:1313 __bread_gfp+0x2d/0x310 fs/buffer.c:1347 sb_bread include/linux/buffer_head.h:307 [inline] fat12_ent_bread+0x14e/0x3d0 fs/fat/fatent.c:75 fat_ent_read_block fs/fat/fatent.c:441 [inline] fat_alloc_clusters+0x8ce/0x16e0 fs/fat/fatent.c:489 fat_add_cluster+0x7a/0x150 fs/fat/inode.c:101 __fat_get_block fs/fat/inode.c:148 [inline] ...
Trivial reproducer for the problem looks like:
truncate -s 1G /tmp/image losetup /dev/loop0 /tmp/image mkfs.ext4 -b 1024 /dev/loop0 mount -t ext4 /dev/loop0 /mnt losetup -c /dev/loop0 l /mnt
Fix the problem by moving initialization of a block device block size into a separate function and call it when needed.
Thanks to Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp for help with debugging the problem.
Reported-by: syzbot+9933e4476f365f5d5a1b@syzkaller.appspotmail.com Signed-off-by: Jan Kara jack@suse.cz Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/block_dev.c | 28 ++++++++++++++++++---------- 1 file changed, 18 insertions(+), 10 deletions(-)
--- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -104,6 +104,20 @@ void invalidate_bdev(struct block_device } EXPORT_SYMBOL(invalidate_bdev);
+static void set_init_blocksize(struct block_device *bdev) +{ + unsigned bsize = bdev_logical_block_size(bdev); + loff_t size = i_size_read(bdev->bd_inode); + + while (bsize < PAGE_SIZE) { + if (size & bsize) + break; + bsize <<= 1; + } + bdev->bd_block_size = bsize; + bdev->bd_inode->i_blkbits = blksize_bits(bsize); +} + int set_blocksize(struct block_device *bdev, int size) { /* Size must be a power of two, and between 512 and PAGE_SIZE */ @@ -1408,18 +1422,9 @@ EXPORT_SYMBOL(check_disk_change);
void bd_set_size(struct block_device *bdev, loff_t size) { - unsigned bsize = bdev_logical_block_size(bdev); - inode_lock(bdev->bd_inode); i_size_write(bdev->bd_inode, size); inode_unlock(bdev->bd_inode); - while (bsize < PAGE_SIZE) { - if (size & bsize) - break; - bsize <<= 1; - } - bdev->bd_block_size = bsize; - bdev->bd_inode->i_blkbits = blksize_bits(bsize); } EXPORT_SYMBOL(bd_set_size);
@@ -1496,8 +1501,10 @@ static int __blkdev_get(struct block_dev } }
- if (!ret) + if (!ret) { bd_set_size(bdev,(loff_t)get_capacity(disk)<<9); + set_init_blocksize(bdev); + }
/* * If the device is invalidated, rescan partition @@ -1532,6 +1539,7 @@ static int __blkdev_get(struct block_dev goto out_clear; } bd_set_size(bdev, (loff_t)bdev->bd_part->nr_sects << 9); + set_init_blocksize(bdev); }
if (bdev->bd_bdi == &noop_backing_dev_info)