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.
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
Link: https://www.mail-archive.com/linux-kernel@xxxxxxxxxxxxxxx/msg2262077.html
Fixes: 1bdc76aea115 ("iov_iter: use bvec iterator to implement iterate_bvec()")
Reported-by: syzbot <syzbot+61acc40a49a3e46e25ea@xxxxxxxxxxxxxxxxxxxxxxxxx>
Tested-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
---
V2:
- fix reported-by tag
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 ac0c7299d5b8..9c4fab5f22a7 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -117,11 +117,18 @@ 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 ? 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) \
--
2.25.2
