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    Subject[PATCH 4.4 112/137] nfs: use file_dentry()
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

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

    From: Miklos Szeredi <mszeredi@redhat.com>

    commit be62a1a8fd116f5cd9e53726601f970e16e17558 upstream.

    NFS may be used as lower layer of overlayfs and accessing f_path.dentry can
    lead to a crash.

    Fix by replacing direct access of file->f_path.dentry with the
    file_dentry() accessor, which will always return a native object.

    Fixes: 4bacc9c9234c ("overlayfs: Make f_path always point to the overlay and f_inode to the underlay")
    Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
    Tested-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
    Acked-by: Trond Myklebust <trond.myklebust@primarydata.com>
    Signed-off-by: Theodore Ts'o <tytso@mit.edu>
    Cc: David Howells <dhowells@redhat.com>
    Cc: Al Viro <viro@zeniv.linux.org.uk>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/nfs/dir.c | 6 +++---
    fs/nfs/inode.c | 2 +-
    fs/nfs/nfs4file.c | 4 ++--
    3 files changed, 6 insertions(+), 6 deletions(-)

    --- a/fs/nfs/dir.c
    +++ b/fs/nfs/dir.c
    @@ -377,7 +377,7 @@ int nfs_readdir_xdr_filler(struct page *
    again:
    timestamp = jiffies;
    gencount = nfs_inc_attr_generation_counter();
    - error = NFS_PROTO(inode)->readdir(file->f_path.dentry, cred, entry->cookie, pages,
    + error = NFS_PROTO(inode)->readdir(file_dentry(file), cred, entry->cookie, pages,
    NFS_SERVER(inode)->dtsize, desc->plus);
    if (error < 0) {
    /* We requested READDIRPLUS, but the server doesn't grok it */
    @@ -560,7 +560,7 @@ int nfs_readdir_page_filler(nfs_readdir_
    count++;

    if (desc->plus != 0)
    - nfs_prime_dcache(desc->file->f_path.dentry, entry);
    + nfs_prime_dcache(file_dentry(desc->file), entry);

    status = nfs_readdir_add_to_array(entry, page);
    if (status != 0)
    @@ -864,7 +864,7 @@ static bool nfs_dir_mapping_need_revalid
    */
    static int nfs_readdir(struct file *file, struct dir_context *ctx)
    {
    - struct dentry *dentry = file->f_path.dentry;
    + struct dentry *dentry = file_dentry(file);
    struct inode *inode = d_inode(dentry);
    nfs_readdir_descriptor_t my_desc,
    *desc = &my_desc;
    --- a/fs/nfs/inode.c
    +++ b/fs/nfs/inode.c
    @@ -927,7 +927,7 @@ int nfs_open(struct inode *inode, struct
    {
    struct nfs_open_context *ctx;

    - ctx = alloc_nfs_open_context(filp->f_path.dentry, filp->f_mode);
    + ctx = alloc_nfs_open_context(file_dentry(filp), filp->f_mode);
    if (IS_ERR(ctx))
    return PTR_ERR(ctx);
    nfs_file_set_open_context(filp, ctx);
    --- a/fs/nfs/nfs4file.c
    +++ b/fs/nfs/nfs4file.c
    @@ -26,7 +26,7 @@ static int
    nfs4_file_open(struct inode *inode, struct file *filp)
    {
    struct nfs_open_context *ctx;
    - struct dentry *dentry = filp->f_path.dentry;
    + struct dentry *dentry = file_dentry(filp);
    struct dentry *parent = NULL;
    struct inode *dir;
    unsigned openflags = filp->f_flags;
    @@ -57,7 +57,7 @@ nfs4_file_open(struct inode *inode, stru
    parent = dget_parent(dentry);
    dir = d_inode(parent);

    - ctx = alloc_nfs_open_context(filp->f_path.dentry, filp->f_mode);
    + ctx = alloc_nfs_open_context(file_dentry(filp), filp->f_mode);
    err = PTR_ERR(ctx);
    if (IS_ERR(ctx))
    goto out;

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