Commit 5db470e2 authored by Jaegeuk Kim's avatar Jaegeuk Kim Committed by Jens Axboe
Browse files

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: default avatarMartijn Coenen <maco@google.com>
Reviewed-by: default avatarBart Van Assche <bvanassche@acm.org>
Signed-off-by: default avatarJaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 649d4968

drivers/block/loop.c

+33 −2
Original line number Diff line number Diff line
@@ -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,

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