If the bio contains no data, bio_first_folio() calls page_folio() on a NULL pointer and oopses. Move the test that we've reached the end of the bio from bio_next_folio() to bio_first_folio().

Reported-by: syzbot+8b23309d5788a79d3eea@syzkaller.appspotmail.com Reported-by: syzbot+004c1e0fced2b4bc3dcc@syzkaller.appspotmail.com Fixes: 640d1930bef4 ("block: Add bio_for_each_folio_all()") Cc: stable@vger.kernel.org Signed-off-by: Matthew Wilcox (Oracle) willy@infradead.org --- include/linux/bio.h | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/include/linux/bio.h b/include/linux/bio.h index ec4db73e5f4e..1518f1201ddd 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -286,6 +286,11 @@ static inline void bio_first_folio(struct folio_iter *fi, struct bio *bio, { struct bio_vec *bvec = bio_first_bvec_all(bio) + i;

+ if (i >= bio->bi_vcnt) { + fi->folio = NULL; + return; + } + fi->folio = page_folio(bvec->bv_page); fi->offset = bvec->bv_offset + PAGE_SIZE * (bvec->bv_page - &fi->folio->page); @@ -303,10 +308,8 @@ static inline void bio_next_folio(struct folio_iter *fi, struct bio *bio) fi->offset = 0; fi->length = min(folio_size(fi->folio), fi->_seg_count); fi->_next = folio_next(fi->folio); - } else if (fi->_i + 1 < bio->bi_vcnt) { - bio_first_folio(fi, bio, fi->_i + 1); } else { - fi->folio = NULL; + bio_first_folio(fi, bio, fi->_i + 1); } }