block: Fix for_each_bvec()

commit b7aa84d9cb9f26da1a9312c3e39dbd1a3c25a426 upstream.

Commit 4550dd6c6b062 introduced for_each_bvec() which iterates over each
bvec attached to a bio or bip. However, the macro fails to check bi_size
before dereferencing which can lead to crashes while counting/mapping
integrity scatterlist segments.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Kent Overstreet <kmo@daterainc.com>
Cc: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/bio.h b/include/linux/bio.h
index 5a4d39b..5aa372a 100644 (file)
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -216,9 +216,9 @@ static inline void bvec_iter_advance(struct bio_vec *bv, struct bvec_iter *iter,
 }
 
 #define for_each_bvec(bvl, bio_vec, iter, start)                       \
-       for ((iter) = start;                                            \
-            (bvl) = bvec_iter_bvec((bio_vec), (iter)),                 \
-               (iter).bi_size;                                         \
+       for (iter = (start);                                            \
+            (iter).bi_size &&                                          \
+               ((bvl = bvec_iter_bvec((bio_vec), (iter))), 1); \
             bvec_iter_advance((bio_vec), &(iter), (bvl).bv_len))