From: Ming Lei ming.lei@redhat.com
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 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
--- include/linux/bvec.h | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
--- a/include/linux/bvec.h +++ b/include/linux/bvec.h @@ -119,10 +119,17 @@ static inline bool bvec_iter_rewind(cons 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 */