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    Subject[PATCH AUTOSEL 4.18 06/92] vfs: fix freeze protection in mnt_want_write_file() for overlayfs
    Date
    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>
    ---
    fs/namespace.c | 7 ++++---
    1 file changed, 4 insertions(+), 3 deletions(-)

    diff --git a/fs/namespace.c b/fs/namespace.c
    index bd2f4c68506a..1949e0939d40 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)
    --
    2.17.1
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