From: Miklos Szeredi <mszeredi@redhat.com>
Date: Wed, 18 Jul 2018 13:44:43 +0000 (+0200)
Subject: vfs: fix freeze protection in mnt_want_write_file() for overlayfs
X-Git-Tag: v4.14.72~58
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=4f4374a9bd25b333971e6f2656b642d29e2efe7b;p=platform%2Fkernel%2Flinux-rpi.git

vfs: fix freeze protection in mnt_want_write_file() for overlayfs

[ Upstream commit a6795a585929d94ca3e931bc8518f8deb8bbe627 ]

The underlying real file used by overlayfs still contains the overlay path.
This results in mnt_want_write_file() calls by the filesystem getting
freeze protection on the wrong inode (the overlayfs one instead of the real
one).

Fix by using file_inode(file)->i_sb instead of file->f_path.mnt->mnt_sb.

Reported-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/fs/namespace.c b/fs/namespace.c
index 9dc146e7..3ee3ee5 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -446,10 +446,10 @@ int mnt_want_write_file_path(struct file *file)
 {
 	int ret;
 
-	sb_start_write(file->f_path.mnt->mnt_sb);
+	sb_start_write(file_inode(file)->i_sb);
 	ret = __mnt_want_write_file(file);
 	if (ret)
-		sb_end_write(file->f_path.mnt->mnt_sb);
+		sb_end_write(file_inode(file)->i_sb);
 	return ret;
 }
 
@@ -540,7 +540,8 @@ void __mnt_drop_write_file(struct file *file)
 
 void mnt_drop_write_file_path(struct file *file)
 {
-	mnt_drop_write(file->f_path.mnt);
+	__mnt_drop_write_file(file);
+	sb_end_write(file_inode(file)->i_sb);
 }
 
 void mnt_drop_write_file(struct file *file)