From b7aae706e84ac271f755a574d6a18fc9b42e8e8f Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Mon, 17 Aug 2020 18:00:55 +0800 Subject: [PATCH] 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 1bdc76aea115 ("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: 1bdc76aea115 ("iov_iter: use bvec iterator to implement iterate_bvec()") Reported-by: syzbot Signed-off-by: Ming Lei Tested-by: Tetsuo Handa Cc: Al Viro Cc: Matthew Wilcox Cc: Link: https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg2262077.html Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- include/linux/bvec.h | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/include/linux/bvec.h b/include/linux/bvec.h index ec8a4d7af6bd..f7dc68cd0a39 100644 --- a/include/linux/bvec.h +++ b/include/linux/bvec.h @@ -119,10 +119,17 @@ static inline bool bvec_iter_rewind(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))) #endif /* __LINUX_BVEC_ITER_H */ -- 2.20.1