If we don't drop caches used in old offset, we can get old data from new
offset, which gives unexpected data to user.
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
This patch drops caches when we change lo->offset.
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: linux-block@xxxxxxxxxxxxxxx
Reported-by: Martijn Coenen <maco@xxxxxxxxxx>
Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
---
drivers/block/loop.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index cb0cc8685076..f073a3f1a7cd 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;
--
2.19.0.605.g01d371f741-goog
