On Tue, Mar 8, 2016 at 10:49 AM, Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
> From: Miklos Szeredi <mszeredi@xxxxxxxxxx>
>
> 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@xxxxxxxxxx>
> Cc: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> Tested-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
Acked-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> ---
> 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
> @@ -940,7 +940,7 @@ 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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