sysfs: Do not return POSIX ACL xattrs via listxattr

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>

1 files changed, 13 insertions, 11 deletions

diff --git a/fs/xattr.c b/fs/xattr.c
index daa732550088..0d6a6a4af861 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -948,17 +948,19 @@ ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
         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