Re: [PATCH v2] loop: drop caches if offset or block_size are changed
From: Jaegeuk Kim <jaegeuk@kernel.org>
Date: 2018-12-17 19:42:40
Also in:
lkml
Subsystem:
block layer, the rest · Maintainers:
Jens Axboe, Linus Torvalds
If we don't drop caches used in old offset or block_size, we can get old data from new offset/block_size, which gives unexpected data to user. For example, Martijn found a loopback bug in the below scenario. 1) LOOP_SET_FD loads first two pages on loop file 2) LOOP_SET_STATUS64 changes the offset on the loop file 3) mount is failed due to the cached pages having wrong superblock Cc: Jens Axboe <axboe@kernel.dk> Cc: linux-block@vger.kernel.org Reported-by: Martijn Coenen <redacted> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> --- v1 to v2: - cover block_size change drivers/block/loop.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index cb0cc8685076..382557c81674 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c@@ -1154,6 +1154,12 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info) if (lo->lo_offset != info->lo_offset || lo->lo_sizelimit != info->lo_sizelimit) { + struct block_device *bdev = lo->lo_device; + + /* drop stale caches used in old offset */ + sync_blockdev(bdev); + kill_bdev(bdev); + if (figure_loop_size(lo, info->lo_offset, info->lo_sizelimit)) { err = -EFBIG; goto exit;
@@ -1388,6 +1394,15 @@ static int loop_set_block_size(struct loop_device *lo, unsigned long arg) blk_queue_io_min(lo->lo_queue, arg); loop_update_dio(lo); + /* Don't change the size if it is same as current */ + if (lo->lo_queue->limits.logical_block_size != arg) { + struct block_device *bdev = lo->lo_device; + + /* drop stale caches likewise set_blocksize */ + sync_blockdev(bdev); + kill_bdev(bdev); + } + blk_mq_unfreeze_queue(lo->lo_queue); return 0;
--
2.19.0.605.g01d371f741-goog