Commit a7297a6a authored Apr 15, 2016 by Ming Lei Committed by Jens Axboe Apr 15, 2016

block: loop: fix filesystem corruption in case of aio/dio



Starting from commit e36f6204(block: split bios to max possible length),
block core starts to split bio in the middle of bvec.

Unfortunately loop dio/aio doesn't consider this situation, and
always treat 'iter.iov_offset' as zero. Then filesystem corruption
is observed.

This patch figures out the offset of the base bvevc via
'bio->bi_iter.bi_bvec_done' and fixes the issue by passing the offset
to iov iterator.

Fixes: e36f6204 (block: split bios to max possible length)
Cc: Keith Busch <keith.busch@intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: stable@vger.kernel.org (4.5)
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

parent a5229050

drivers/block/loop.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -488,6 +488,12 @@ static int lo_rw_aio(struct loop_device lo, struct loop_cmd cmd,
		bvec = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
		iov_iter_bvec(&iter, ITER_BVEC \| rw, bvec,
		bio_segments(bio), blk_rq_bytes(cmd->rq));
		/*
		* This bio may be started from the middle of the 'bvec'
		* because of bio splitting, so offset from the bvec must
		* be passed to iov iterator
		*/
		iter.iov_offset = bio->bi_iter.bi_bvec_done;

		cmd->iocb.ki_pos = pos;
		cmd->iocb.ki_filp = file;

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