[PATCH] NFS: NFSv2/v3 clients should never be setting NFS_CAP_XATTR

[Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>]

Ensure that we always initialise the 'xattr_support' field in struct
nfs_fsinfo, so that nfs_server_set_fsinfo() doesn't declare our NFSv2/v3
client to be capable of supporting the NFSv4.2 xattr protocol by setting
the NFS_CAP_XATTR capability.

This configuration can cause nfs_do_access() to set access mode bits
that are unsupported by the NFSv3 ACCESS call, which may confuse
spec-compliant servers.

Reported-by: Olga Kornievskaia <kolga@xxxxxxxxxx>
Fixes: b78ef845c35d ("NFSv4.2: query the server for extended attribute support")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>

diff --git a/fs/nfs/nfs3xdr.c b/fs/nfs/nfs3xdr.c
index 9274c9c5efea..54a1d21cbcc6 100644
--- a/fs/nfs/nfs3xdr.c
+++ b/fs/nfs/nfs3xdr.c
@@ -2228,6 +2228,7 @@ static int decode_fsinfo3resok(struct xdr_stream *xdr,
 	/* ignore properties */
 	result->lease_time = 0;
 	result->change_attr_type = NFS4_CHANGE_TYPE_IS_UNDEFINED;
+	result->xattr_support = 0;
 	return 0;
 }
 
diff --git a/fs/nfs/proc.c b/fs/nfs/proc.c
index 73dcaa99fa9b..e3570c656b0f 100644
--- a/fs/nfs/proc.c
+++ b/fs/nfs/proc.c
@@ -92,6 +92,7 @@ nfs_proc_get_root(struct nfs_server *server, struct nfs_fh *fhandle,
 	info->maxfilesize = 0x7FFFFFFF;
 	info->lease_time = 0;
 	info->change_attr_type = NFS4_CHANGE_TYPE_IS_UNDEFINED;
+	info->xattr_support = 0;
 	return 0;
 }