This is a note to let you know that I've just added the patch titled
f2fs: fix dereference of stale list iterator after loop body
to the 5.18-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:
f2fs-fix-dereference-of-stale-list-iterator-after-lo.patch
and it can be found in the queue-5.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 1eb109bf820b56119dbf704779882bf0a756f247
Author: Jakob Koschel <jakobkoschel@xxxxxxxxx>
Date: Fri Apr 1 00:34:14 2022 +0200
f2fs: fix dereference of stale list iterator after loop body
[ Upstream commit 2aaf51dd39afb6d01d13f1e6fe20b684733b37d5 ]
The list iterator variable will be a bogus pointer if no break was hit.
Dereferencing it (cur->page in this case) could load an out-of-bounds/undefined
value making it unsafe to use that in the comparision to determine if the
specific element was found.
Since 'cur->page' *can* be out-ouf-bounds it cannot be guaranteed that
by chance (or intention of an attacker) it matches the value of 'page'
even though the correct element was not found.
This is fixed by using a separate list iterator variable for the loop
and only setting the original variable if a suitable element was found.
Then determing if the element was found is simply checking if the
variable is set.
Fixes: 8c242db9b8c0 ("f2fs: fix stale ATOMIC_WRITTEN_PAGE private pointer")
Signed-off-by: Jakob Koschel <jakobkoschel@xxxxxxxxx>
Reviewed-by: Chao Yu <chao@xxxxxxxxxx>
Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index bd9731cdec56..9dd9f88b75e9 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -355,16 +355,19 @@ void f2fs_drop_inmem_page(struct inode *inode, struct page *page)
struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
struct list_head *head = &fi->inmem_pages;
struct inmem_pages *cur = NULL;
+ struct inmem_pages *tmp;
f2fs_bug_on(sbi, !page_private_atomic(page));
mutex_lock(&fi->inmem_lock);
- list_for_each_entry(cur, head, list) {
- if (cur->page == page)
+ list_for_each_entry(tmp, head, list) {
+ if (tmp->page == page) {
+ cur = tmp;
break;
+ }
}
- f2fs_bug_on(sbi, list_empty(head) || cur->page != page);
+ f2fs_bug_on(sbi, !cur);
list_del(&cur->list);
mutex_unlock(&fi->inmem_lock);
