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@xxxxxxxxx>
Cc: linux-block@xxxxxxxxxxxxxxx
Reported-by: Martijn Coenen <maco@xxxxxxxxxx>
Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
---
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
