[PATCH 4.9 026/310] NFSv4.1: Work around a Linux server bug...

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>


[ Upstream commit f4b23de3dda1536590787c9e5c3d16b8738ab108 ]

It turns out the Linux server has a bug in its implementation of
supattr_exclcreat; it returns the set of all attributes, whether
or not they are supported by minor version 1.
In order to avoid a regression, we therefore apply the supported_attrs
as a mask on top of whatever the server sent us.

Reported-by: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 fs/nfs/nfs4proc.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -3300,6 +3300,7 @@ static int _nfs4_server_capabilities(str
 		.rpc_resp = &res,
 	};
 	int status;
+	int i;
 
 	bitmask[0] = FATTR4_WORD0_SUPPORTED_ATTRS |
 		     FATTR4_WORD0_FH_EXPIRE_TYPE |
@@ -3365,8 +3366,13 @@ static int _nfs4_server_capabilities(str
 		server->cache_consistency_bitmask[0] &= FATTR4_WORD0_CHANGE|FATTR4_WORD0_SIZE;
 		server->cache_consistency_bitmask[1] &= FATTR4_WORD1_TIME_METADATA|FATTR4_WORD1_TIME_MODIFY;
 		server->cache_consistency_bitmask[2] = 0;
+
+		/* Avoid a regression due to buggy server */
+		for (i = 0; i < ARRAY_SIZE(res.exclcreat_bitmask); i++)
+			res.exclcreat_bitmask[i] &= res.attr_bitmask[i];
 		memcpy(server->exclcreat_bitmask, res.exclcreat_bitmask,
 			sizeof(server->exclcreat_bitmask));
+
 		server->acl_bitmask = res.acl_bitmask;
 		server->fh_expire_type = res.fh_expire_type;
 	}