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Subject[PATCH 4.18 151/235] vfs: fix freeze protection in mnt_want_write_file() for overlayfs
Date
4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Miklos Szeredi <mszeredi@redhat.com>

[ 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>
---
fs/namespace.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -446,10 +446,10 @@ int mnt_want_write_file_path(struct 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 *

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)

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