[PATCH 5.8 049/255] f2fs: fix use-after-free issue

From: Greg Kroah-Hartman
Date: Tue Sep 01 2020 - 11:42:13 EST


From: Li Guifu <bluce.liguifu@xxxxxxxxxx>

[ 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@xxxxxxxxxx>
Reviewed-by: Chao Yu <yuchao0@xxxxxxxxxx>
Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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 20e56b0fa46a9..0deb839da0a03 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -1173,6 +1173,9 @@ 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 */
@@ -1238,8 +1241,6 @@ 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