This is a note to let you know that I've just added the patch titled
fix unbalanced page refcounting in bio_map_user_iov
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
fix-unbalanced-page-refcounting-in-bio_map_user_iov.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 95d78c28b5a85bacbc29b8dba7c04babb9b0d467 Mon Sep 17 00:00:00 2001
From: Vitaly Mayatskikh <v.mayatskih@xxxxxxxxx>
Date: Fri, 22 Sep 2017 01:18:39 -0400
Subject: fix unbalanced page refcounting in bio_map_user_iov
From: Vitaly Mayatskikh <v.mayatskih@xxxxxxxxx>
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@xxxxxxxxx>
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
block/bio.c | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/block/bio.c
+++ b/block/bio.c
@@ -1318,6 +1318,7 @@ struct bio *bio_map_user_iov(struct requ
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 requ
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;
}
Patches currently in stable-queue which might be from v.mayatskih@xxxxxxxxx are
queue-4.9/fix-unbalanced-page-refcounting-in-bio_map_user_iov.patch