NFS: Fix inode corruption in nfs_prime_dcache()

Due to inode number reuse in filesystems, we can end up corrupting the
inode on our client if we apply the file attributes without ensuring that
the filehandle matches.
Typical symptoms include spurious "mode changed" reports in the syslog.

We still do want to ensure that we don't invalidate the dentry if the
inode number matches, but we don't have a filehandle.

Fixes: fa9233699cc1 ("NFS: Don't require a filehandle to refresh...")
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Cc: stable@vger.kernel.org # v4.0+
Tested-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index eb095f77c39d0277762ee543c9fea38fdbcf98ab..2bade7909dec6bee8fcf1464890f0f2365037efe 100644 (file)
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -435,11 +435,11 @@ int nfs_same_file(struct dentry *dentry, struct nfs_entry *entry)
                return 0;
 
        nfsi = NFS_I(inode);
-       if (entry->fattr->fileid == nfsi->fileid)
-               return 1;
-       if (nfs_compare_fh(entry->fh, &nfsi->fh) == 0)
-               return 1;
-       return 0;
+       if (entry->fattr->fileid != nfsi->fileid)
+               return 0;
+       if (entry->fh->size && nfs_compare_fh(entry->fh, &nfsi->fh) != 0)
+               return 0;
+       return 1;
 }
 
 static
@@ -525,6 +525,8 @@ again:
                                        &entry->fattr->fsid))
                        goto out;
                if (nfs_same_file(dentry, entry)) {
+                       if (!entry->fh->size)
+                               goto out;
                        nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
                        status = nfs_refresh_inode(d_inode(dentry), entry->fattr);
                        if (!status)
@@ -537,6 +539,10 @@ again:
                        goto again;
                }
        }
+       if (!entry->fh->size) {
+               d_lookup_done(dentry);
+               goto out;
+       }
 
        inode = nfs_fhget(dentry->d_sb, entry->fh, entry->fattr, entry->label);
        alias = d_splice_alias(inode, dentry);