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block: allow for_each_bvec to support zero len bvec 

commit 7e24969022cbd61ddc586f14824fc205661bb124 upstream.

Block layer usually doesn't support or allow zero-length bvec. Since
commit 1bdc76aea1 ("iov_iter: use bvec iterator to implement
iterate_bvec()"), iterate_bvec() switches to bvec iterator. However,
Al mentioned that 'Zero-length segments are not disallowed' in iov_iter.

Fixes for_each_bvec() so that it can move on after seeing one zero
length bvec.

Fixes: 1bdc76aea1 ("iov_iter: use bvec iterator to implement iterate_bvec()")
Reported-by: syzbot <syzbot+61acc40a49a3e46e25ea@syzkaller.appspotmail.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Tested-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: <stable@vger.kernel.org>
Link: https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg2262077.html
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ming Lei 2020-08-17 18:00:55 +08:00 committed by Greg Kroah-Hartman
parent b6e4827c04
commit 84c041c124
1 changed files with 8 additions and 1 deletions
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9
include/linux/bvec.h
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@ -110,11 +110,18 @@ static inline bool bvec_iter_advance(const struct bio_vec *bv,
return true;
}
static inline void bvec_iter_skip_zero_bvec(struct bvec_iter *iter)
{
iter->bi_bvec_done = 0;
iter->bi_idx++;
}
#define for_each_bvec(bvl, bio_vec, iter, start) \
for (iter = (start); \
(iter).bi_size && \
((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \
bvec_iter_advance((bio_vec), &(iter), (bvl).bv_len))
(bvl).bv_len ? (void)bvec_iter_advance((bio_vec), &(iter), \
(bvl).bv_len) : bvec_iter_skip_zero_bvec(&(iter)))
/* for iterating one bio from start to end */
#define BVEC_ITER_ALL_INIT (struct bvec_iter) \