afs: Stop listxattr() from listing "afs.*" attributes

commit a7889c6320b9200e3fe415238f546db677310fa9 upstream.

afs_listxattr() lists all the available special afs xattrs (i.e. those in
the "afs.*" space), no matter what type of server we're dealing with.  But
OpenAFS servers, for example, cannot deal with some of the extra-capable
attributes that AuriStor (YFS) servers provide.  Unfortunately, the
presence of the afs.yfs.* attributes causes errors[1] for anything that
tries to read them if the server is of the wrong type.

Fix the problem by removing afs_listxattr() so that none of the special
xattrs are listed (AFS doesn't support xattrs).  It does mean, however,
that getfattr won't list them, though they can still be accessed with
getxattr() and setxattr().

This can be tested with something like:

	getfattr -d -m ".*" /afs/example.com/path/to/file

With this change, none of the afs.* attributes should be visible.

Changes:
ver #2:
 - Hide all of the afs.* xattrs, not just the ACL ones.

Fixes: ae46578b963f ("afs: Get YFS ACLs and information through xattrs")
Reported-by: Gaja Sophie Peters <gaja.peters@math.uni-hamburg.de>
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Gaja Sophie Peters <gaja.peters@math.uni-hamburg.de>
Reviewed-by: Jeffrey Altman <jaltman@auristor.com>
Reviewed-by: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Link: http://lists.infradead.org/pipermail/linux-afs/2021-March/003502.html [1]
Link: http://lists.infradead.org/pipermail/linux-afs/2021-March/003567.html # v1
Link: http://lists.infradead.org/pipermail/linux-afs/2021-March/003573.html # v2
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 0 insertions, 23 deletions

diff --git a/fs/afs/xattr.c b/fs/afs/xattr.c
index 5552d034090a..13292d4ca860 100644
--- a/fs/afs/xattr.c
+++ b/fs/afs/xattr.c
@@ -11,29 +11,6 @@
 #include <linux/xattr.h>
 #include "internal.h"
 
-static const char afs_xattr_list[] =
-	"afs.acl\0"
-	"afs.cell\0"
-	"afs.fid\0"
-	"afs.volume\0"
-	"afs.yfs.acl\0"
-	"afs.yfs.acl_inherited\0"
-	"afs.yfs.acl_num_cleaned\0"
-	"afs.yfs.vol_acl";
-
-/*
- * Retrieve a list of the supported xattrs.
- */
-ssize_t afs_listxattr(struct dentry *dentry, char *buffer, size_t size)
-{
-	if (size == 0)
-		return sizeof(afs_xattr_list);
-	if (size < sizeof(afs_xattr_list))
-		return -ERANGE;
-	memcpy(buffer, afs_xattr_list, sizeof(afs_xattr_list));
-	return sizeof(afs_xattr_list);
-}
-
 /*
  * Get a file's ACL.
  */