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

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Message-Id: <20200901150955.233010981@linuxfoundation.org>
Date:   Tue,  1 Sep 2020 17:08:47 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Li Guifu <bluce.liguifu@...wei.com>,
        Chao Yu <yuchao0@...wei.com>, Jaegeuk Kim <jaegeuk@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 047/214] f2fs: fix use-after-free issue

From: Li Guifu <bluce.liguifu@...wei.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@...wei.com>
Reviewed-by: Chao Yu <yuchao0@...wei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.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