From d5e8c2a94379adad9caeb88c3d72a1c1f9d462c2 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 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 Signed-off-by: Al Viro (cherry picked from commit 95d78c28b5a85bacbc29b8dba7c04babb9b0d467) Orabug: 27062562 CVE: CVE-2017-12190 Signed-off-by: Kirtikar Kashyap Reviewed-by: Ethan Zhao --- block/bio.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/block/bio.c b/block/bio.c index 6e31ceacd4a9..f4cbd84b0abf 100644 --- a/block/bio.c +++ b/block/bio.c @@ -1367,6 +1367,7 @@ 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; @@ -1381,6 +1382,13 @@ 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; } -- 2.50.1