[PATCH 4.9 52/59] sysfs: Do not return POSIX ACL xattrs via listxattr

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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

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

From: Andreas Gruenbacher <agruenba@redhat.com>

commit ffc4c92227db5699493e43eb140b4cb5904c30ff upstream.

Commit 786534b92f3c introduced a regression that caused listxattr to
return the POSIX ACL attribute names even though sysfs doesn't support
POSIX ACLs.  This happens because simple_xattr_list checks for NULL
i_acl / i_default_acl, but inode_init_always initializes those fields
to ACL_NOT_CACHED ((void *)-1).  For example:
    $ getfattr -m- -d /sys
    /sys: system.posix_acl_access: Operation not supported
    /sys: system.posix_acl_default: Operation not supported
Fix this in simple_xattr_list by checking if the filesystem supports POSIX ACLs.

Fixes: 786534b92f3c ("tmpfs: listxattr should include POSIX ACL xattrs")
Reported-by:  Marc Aurèle La France <tsi@tuyoix.net>
Tested-by: Marc Aurèle La France <tsi@tuyoix.net>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Cc: stable@vger.kernel.org # v4.5+
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/xattr.c |   24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -953,17 +953,19 @@ ssize_t simple_xattr_list(struct inode *
 	int err = 0;
 
 #ifdef CONFIG_FS_POSIX_ACL
-	if (inode->i_acl) {
-		err = xattr_list_one(&buffer, &remaining_size,
-				     XATTR_NAME_POSIX_ACL_ACCESS);
-		if (err)
-			return err;
-	}
-	if (inode->i_default_acl) {
-		err = xattr_list_one(&buffer, &remaining_size,
-				     XATTR_NAME_POSIX_ACL_DEFAULT);
-		if (err)
-			return err;
+	if (IS_POSIXACL(inode)) {
+		if (inode->i_acl) {
+			err = xattr_list_one(&buffer, &remaining_size,
+					     XATTR_NAME_POSIX_ACL_ACCESS);
+			if (err)
+				return err;
+		}
+		if (inode->i_default_acl) {
+			err = xattr_list_one(&buffer, &remaining_size,
+					     XATTR_NAME_POSIX_ACL_DEFAULT);
+			if (err)
+				return err;
+		}
 	}
 #endif