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loop: drop caches if offset or block_size are changed 

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 <maco@google.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jaegeuk Kim 2019-01-09 19:17:14 -08:00 committed by Jens Axboe
parent 649d496886
commit 5db470e229
1 changed files with 33 additions and 2 deletions
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35
drivers/block/loop.c
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@ -1190,6 +1190,12 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
goto out_unlock;
}
if (lo->lo_offset != info->lo_offset ||
lo->lo_sizelimit != info->lo_sizelimit) {
sync_blockdev(lo->lo_device);
kill_bdev(lo->lo_device);
}
/* I/O need to be drained during transfer transition */
blk_mq_freeze_queue(lo->lo_queue);
@ -1218,6 +1224,14 @@ 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) {
/* kill_bdev should have truncated all the pages */
if (lo->lo_device->bd_inode->i_mapping->nrpages) {
err = -EAGAIN;
pr_warn("%s: loop%d (%s) has still dirty pages (nrpages=%lu)\n",
__func__, lo->lo_number, lo->lo_file_name,
lo->lo_device->bd_inode->i_mapping->nrpages);
goto out_unfreeze;
}
if (figure_loop_size(lo, info->lo_offset, info->lo_sizelimit)) {
err = -EFBIG;
goto out_unfreeze;
@ -1443,22 +1457,39 @@ static int loop_set_dio(struct loop_device *lo, unsigned long arg)
static int loop_set_block_size(struct loop_device *lo, unsigned long arg)
{
int err = 0;
if (lo->lo_state != Lo_bound)
return -ENXIO;
if (arg < 512 || arg > PAGE_SIZE || !is_power_of_2(arg))
return -EINVAL;
if (lo->lo_queue->limits.logical_block_size != arg) {
sync_blockdev(lo->lo_device);
kill_bdev(lo->lo_device);
}
blk_mq_freeze_queue(lo->lo_queue);
/* kill_bdev should have truncated all the pages */
if (lo->lo_queue->limits.logical_block_size != arg &&
lo->lo_device->bd_inode->i_mapping->nrpages) {
err = -EAGAIN;
pr_warn("%s: loop%d (%s) has still dirty pages (nrpages=%lu)\n",
__func__, lo->lo_number, lo->lo_file_name,
lo->lo_device->bd_inode->i_mapping->nrpages);
goto out_unfreeze;
}
blk_queue_logical_block_size(lo->lo_queue, arg);
blk_queue_physical_block_size(lo->lo_queue, arg);
blk_queue_io_min(lo->lo_queue, arg);
loop_update_dio(lo);
out_unfreeze:
blk_mq_unfreeze_queue(lo->lo_queue);
return 0;
return err;
}
static int lo_simple_ioctl(struct loop_device *lo, unsigned int cmd,