nfs: use file_dentry()

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: <stable@vger.kernel.org> # v4.2
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 4bfa7d8bcadee27ab9a6779b3d427170f98ac918..a89d32a38e88720b1905faa0464e1522ba3714a4 100644 (file)
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -377,7 +377,7 @@ int nfs_readdir_xdr_filler(struct page **pages, nfs_readdir_descriptor_t *desc,
  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_descriptor_t *desc, struct nfs_entry *en
                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_revalidate(struct inode *dir)
  */
 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;

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 86faecf8f328f2639bab1c5f7391df6d659610f2..847b678af4f09013c083e17bcef5ecf7f7ee84d2 100644 (file)
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -940,7 +940,7 @@ int nfs_open(struct inode *inode, struct file *filp)
 {
        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);

diff --git a/fs/nfs/nfs4file.c b/fs/nfs/nfs4file.c
index 57ca1c8039c1e00bfcb6e9bb4d8fe7e40f4578d5..2a9ff14cfb3b7a475ce9fe75d3fba813a8396c87 100644 (file)
--- 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, struct file *filp)
        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;