lkml.org 
[lkml]   [2017]   [Sep]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Subject[PATCH] ksm: Fix unlocked iteration over vmas in cmp_and_merge_page()
From
Date
In this place mm is unlocked, so vmas or list may change.
Down read mmap_sem to protect them from modifications.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
(and compile-tested-by)
---
mm/ksm.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/ksm.c b/mm/ksm.c
index db20f8436bc3..86f0db3d6cdb 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1990,6 +1990,7 @@ static void stable_tree_append(struct rmap_item *rmap_item,
*/
static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
{
+ struct mm_struct *mm = rmap_item->mm;
struct rmap_item *tree_rmap_item;
struct page *tree_page = NULL;
struct stable_node *stable_node;
@@ -2062,9 +2063,11 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
if (ksm_use_zero_pages && (checksum == zero_checksum)) {
struct vm_area_struct *vma;

- vma = find_mergeable_vma(rmap_item->mm, rmap_item->address);
+ down_read(&mm->mmap_sem);
+ vma = find_mergeable_vma(mm, rmap_item->address);
err = try_to_merge_one_page(vma, page,
ZERO_PAGE(rmap_item->address));
+ up_read(&mm->mmap_sem);
/*
* In case of failure, the page was not really empty, so we
* need to continue. Otherwise we're done.
\
 
 \ /
  Last update: 2017-09-11 13:06    [W:0.067 / U:0.704 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site