[PATCH 06/10] block: Split out bio_list_copy_data()

Kent Overstreet
2018-05-09T01:33:54Z

Found a bug (with ASAN) where we were passing a bio to bio_copy_data()
with bi_next not NULL, when it should have been - a driver had left
bi_next set to something after calling bio_endio().

Since the normal case is only copying single bios, split out
bio_list_copy_data() to avoid more bugs like this in the future.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
---
block/bio.c | 83 +++++++++++++++++++++++++----------------
drivers/block/pktcdvd.c | 2 +-
include/linux/bio.h | 5 ++-
3 files changed, 55 insertions(+), 35 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index d7bd765e9e..c58544d4bc 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -971,32 +971,16 @@ void bio_advance(struct bio *bio, unsigned bytes)
}
EXPORT_SYMBOL(bio_advance);

-void bio_copy_data_iter(struct bio *dst, struct bvec_iter dst_iter,
- struct bio *src, struct bvec_iter src_iter)
+void bio_copy_data_iter(struct bio *dst, struct bvec_iter *dst_iter,
+ struct bio *src, struct bvec_iter *src_iter)
{
struct bio_vec src_bv, dst_bv;
void *src_p, *dst_p;
unsigned bytes;

- while (1) {
- if (!src_iter.bi_size) {
- src = src->bi_next;
- if (!src)
- break;
-
- src_iter = src->bi_iter;
- }
-
- if (!dst_iter.bi_size) {
- dst = dst->bi_next;
- if (!dst)
- break;
-
- dst_iter = dst->bi_iter;
- }
-
- src_bv = bio_iter_iovec(src, src_iter);
- dst_bv = bio_iter_iovec(dst, dst_iter);
+ while (src_iter->bi_size && dst_iter->bi_size) {
+ src_bv = bio_iter_iovec(src, *src_iter);
+ dst_bv = bio_iter_iovec(dst, *dst_iter);

bytes = min(src_bv.bv_len, dst_bv.bv_len);

@@ -1010,31 +994,66 @@ void bio_copy_data_iter(struct bio *dst, struct bvec_iter dst_iter,
kunmap_atomic(dst_p);
kunmap_atomic(src_p);

- bio_advance_iter(src, &src_iter, bytes);
- bio_advance_iter(dst, &dst_iter, bytes);
+ bio_advance_iter(src, src_iter, bytes);
+ bio_advance_iter(dst, dst_iter, bytes);
}
}
EXPORT_SYMBOL(bio_copy_data_iter);

/**
- * bio_copy_data - copy contents of data buffers from one chain of bios to
- * another
- * @src: source bio list
- * @dst: destination bio list
- *
- * If @src and @dst are single bios, bi_next must be NULL - otherwise, treats
- * @src and @dst as linked lists of bios.
+ * bio_copy_data - copy contents of data buffers from one bio to another
+ * @src: source bio
+ * @dst: destination bio
*
* Stops when it reaches the end of either @src or @dst - that is, copies
* min(src->bi_size, dst->bi_size) bytes (or the equivalent for lists of bios).
*/
void bio_copy_data(struct bio *dst, struct bio *src)
{
- bio_copy_data_iter(dst, dst->bi_iter,
- src, src->bi_iter);
+ struct bvec_iter src_iter = src->bi_iter;
+ struct bvec_iter dst_iter = dst->bi_iter;
+
+ bio_copy_data_iter(dst, &dst_iter, src, &src_iter);
}
EXPORT_SYMBOL(bio_copy_data);

+/**
+ * bio_list_copy_data - copy contents of data buffers from one chain of bios to
+ * another
+ * @src: source bio list
+ * @dst: destination bio list
+ *
+ * Stops when it reaches the end of either the @src list or @dst list - that is,
+ * copies min(src->bi_size, dst->bi_size) bytes (or the equivalent for lists of
+ * bios).
+ */
+void bio_list_copy_data(struct bio *dst, struct bio *src)
+{
+ struct bvec_iter src_iter = src->bi_iter;
+ struct bvec_iter dst_iter = dst->bi_iter;
+
+ while (1) {
+ if (!src_iter.bi_size) {
+ src = src->bi_next;
+ if (!src)
+ break;
+
+ src_iter = src->bi_iter;
+ }
+
+ if (!dst_iter.bi_size) {
+ dst = dst->bi_next;
+ if (!dst)
+ break;
+
+ dst_iter = dst->bi_iter;
+ }
+
+ bio_copy_data_iter(dst, &dst_iter, src, &src_iter);
+ }
+}
+EXPORT_SYMBOL(bio_list_copy_data);
+
struct bio_map_data {
int is_our_pages;
struct iov_iter iter;
diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
index c61d20c9f3..00ea788b17 100644
--- a/drivers/block/pktcdvd.c
+++ b/drivers/block/pktcdvd.c
@@ -1285,7 +1285,7 @@ static void pkt_start_write(struct pktcdvd_device *pd, struct packet_data *pkt)
* Fill-in bvec with data from orig_bios.
*/
spin_lock(&pkt->lock);
- bio_copy_data(pkt->w_bio, pkt->orig_bios.head);
+ bio_list_copy_data(pkt->w_bio, pkt->orig_bios.head);

pkt_set_state(pkt, PACKET_WRITE_WAIT_STATE);
spin_unlock(&pkt->lock);
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 5a6ee955a8..98b175cc00 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -505,9 +505,10 @@ static inline void bio_flush_dcache_pages(struct bio *bi)
}
#endif

-extern void bio_copy_data_iter(struct bio *dst, struct bvec_iter dst_iter,
- struct bio *src, struct bvec_iter src_iter);
+extern void bio_copy_data_iter(struct bio *dst, struct bvec_iter *dst_iter,
+ struct bio *src, struct bvec_iter *src_iter);
extern void bio_copy_data(struct bio *dst, struct bio *src);
+extern void bio_list_copy_data(struct bio *dst, struct bio *src);
extern void bio_free_pages(struct bio *bio);

extern struct bio *bio_copy_user_iov(struct request_queue *,
--
2.17.0