Commit 6bedf00e authored Apr 17, 2019 by Ming Lei Committed by Jens Axboe Apr 19, 2019

block: make sure that bvec length can't be overflow



bvec->bv_offset may be bigger than PAGE_SIZE sometimes, such as,
when one bio is splitted in the middle of one bvec via bio_split(),
and bi_iter.bi_bvec_done is used to build offset of the 1st bvec of
remained bio. And the remained bio's bvec may be re-submitted to fs
layer via ITER_IBVEC, such as loop and nvme-loop.

So we have to make sure that every bvec's offset is less than
PAGE_SIZE from bio_for_each_segment_all() because some drivers(loop,
nvme-loop) passes the splitted bvec to fs layer via ITER_BVEC.

This patch fixes this issue reported by Zhang Yi When running nvme/011.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Yi Zhang <yi.zhang@redhat.com>
Reported-by: Yi Zhang <yi.zhang@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Fixes: 6dc4f100 ("block: allow bio_for_each_segment_all() to iterate over multi-page bvec")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent b40fabc0

include/linux/bvec.h

+3 −2

Original line number	Diff line number	Diff line
		@@ -160,8 +160,9 @@ static inline void bvec_advance(const struct bio_vec *bvec,
		bv->bv_page = nth_page(bv->bv_page, 1);
		bv->bv_offset = 0;
		} else {
		bv->bv_page = bvec->bv_page;
		bv->bv_offset = bvec->bv_offset;
		bv->bv_page = bvec_nth_page(bvec->bv_page, bvec->bv_offset /
		PAGE_SIZE);
		bv->bv_offset = bvec->bv_offset & ~PAGE_MASK;
		}
		bv->bv_len = min_t(unsigned int, PAGE_SIZE - bv->bv_offset,
		bvec->bv_len - iter_all->done);

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