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authorVitaly Mayatskikh <v.mayatskih@gmail.com>2017-09-22 08:18:39 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-10-18 10:35:41 +0300
commit5444d8ab9a1406af9f1bc2f00c26838637542480 (patch)
tree4470222da245ca5e9c56152c86858c1c5841b18f /block
parentf9139a1a2457323894c1780f0e44271af807346d (diff)
downloadlinux-5444d8ab9a1406af9f1bc2f00c26838637542480.tar.xz
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 <v.mayatskih@gmail.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'block')
-rw-r--r--block/bio.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/block/bio.c b/block/bio.c
index 655c9016052a..095382c4315c 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1318,6 +1318,7 @@ 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;
@@ -1332,6 +1333,13 @@ 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;
}