From 9ff5d8fe36745867da8a028b3ea58629f7546155 Mon Sep 17 00:00:00 2001 From: Vitaly Mayatskikh Date: Fri, 22 Sep 2017 01:18:39 -0400 Subject: [PATCH] fix unbalanced page refcounting in bio_map_user_iov commit 95d78c28b5a85bacbc29b8dba7c04babb9b0d467 upstream. 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. Signed-off-by: Vitaly Mayatskikh Signed-off-by: Al Viro [bwh: Backported to 3.2: adjust filename] Signed-off-by: Ben Hutchings --- fs/bio.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/fs/bio.c b/fs/bio.c index 55b51881e751..1fa6b825240d 100644 --- a/fs/bio.c +++ b/fs/bio.c @@ -1027,6 +1027,7 @@ static struct bio *__bio_map_user_iov(struct request_queue *q, offset = uaddr & ~PAGE_MASK; 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; @@ -1041,6 +1042,13 @@ static 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; } -- 2.39.2