[PATCH 5.4 047/214] f2fs: fix use-after-free issue

Greg Kroah-Hartman
2020-09-01T15:31:44Z

From: Li Guifu <bluce.liguifu@huawei.com>

[ Upstream commit 99c787cfd2bd04926f1f553b30bd7dcea2caaba1 ]

During umount, f2fs_put_super() unregisters procfs entries after
f2fs_destroy_segment_manager(), it may cause use-after-free
issue when umount races with procfs accessing, fix it by relocating
f2fs_unregister_sysfs().

[Chao Yu: change commit title/message a bit]

Signed-off-by: Li Guifu <bluce.liguifu@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/f2fs/super.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index f4b882ee48ddf..fa461db696e79 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -1075,6 +1075,9 @@ static void f2fs_put_super(struct super_block *sb)
int i;
bool dropped;

+ /* unregister procfs/sysfs entries in advance to avoid race case */
+ f2fs_unregister_sysfs(sbi);
+
f2fs_quota_off_umount(sb);

/* prevent remaining shrinker jobs */
@@ -1138,8 +1141,6 @@ static void f2fs_put_super(struct super_block *sb)

kvfree(sbi->ckpt);

- f2fs_unregister_sysfs(sbi);
-
sb->s_fs_info = NULL;
if (sbi->s_chksum_driver)
crypto_free_shash(sbi->s_chksum_driver);
--
2.25.1