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authorVitaly Mayatskikh <v.mayatskih@gmail.com>2017-09-22 01:18:39 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2017-10-10 23:54:51 -0400
commit95d78c28b5a85bacbc29b8dba7c04babb9b0d467 (patch)
tree171528916186018b071110eced6ebc55f5d6b3c3
parent899f0429c7d3eed886406cd72182bee3b96aa1f9 (diff)
fix unbalanced page refcounting in bio_map_user_iov
bio_map_user_iov and bio_unmap_user do unbalanced pages refcounting if IO vector has small consecutive buffers belonging to the same page. bio_add_pc_page merges them into one, but the page reference is never dropped. Cc: stable@vger.kernel.org Signed-off-by: Vitaly Mayatskikh <v.mayatskih@gmail.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-rw-r--r--block/bio.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/block/bio.c b/block/bio.c
index b38e962fa83e..0d6439e89acb 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1383,6 +1383,7 @@ struct bio *bio_map_user_iov(struct request_queue *q,
offset = offset_in_page(uaddr);
for (j = cur_page; j < page_limit; j++) {
unsigned int bytes = PAGE_SIZE - offset;
+ unsigned short prev_bi_vcnt = bio->bi_vcnt;
if (len <= 0)
break;
@@ -1397,6 +1398,13 @@ struct bio *bio_map_user_iov(struct request_queue *q,
bytes)
break;
+ /*
+ * check if vector was merged with previous
+ * drop page reference if needed
+ */
+ if (bio->bi_vcnt == prev_bi_vcnt)
+ put_page(pages[j]);
+
len -= bytes;
offset = 0;
}