Code: int orangefs_set_acl(struct inode *inode, struct posix_acl *acl, int type)
{
	struct orangefs_inode_s *orangefs_inode = ORANGEFS_I(inode);
	int error = 0;
	void *value = NULL;
	size_t size = 0;
	const char *name = NULL;

	switch (type) {
 	case ACL_TYPE_ACCESS:
 		name = XATTR_NAME_POSIX_ACL_ACCESS;
 		if (acl) {
			umode_t mode = inode->i_mode;
			/*
			 * can we represent this with the traditional file
			 * mode permission bits?
			 */
			error = posix_acl_equiv_mode(acl, &mode);
			if (error < 0) {
				gossip_err("%s: posix_acl_equiv_mode err: %d\n",
 					   __func__,
 					   error);
 				return error;
			}

			if (inode->i_mode != mode)
 				SetModeFlag(orangefs_inode);
 			inode->i_mode = mode;
 			mark_inode_dirty_sync(inode);
			if (error == 0)
				acl = NULL;
 		}
 		break;
 	case ACL_TYPE_DEFAULT:
		name = XATTR_NAME_POSIX_ACL_DEFAULT;
		break;
	default:
		gossip_err("%s: invalid type %d!\n", __func__, type);
		return -EINVAL;
	}

	gossip_debug(GOSSIP_ACL_DEBUG,
		     "%s: inode %pU, key %s type %d\n",
		     __func__, get_khandle_from_ino(inode),
		     name,
		     type);

	if (acl) {
		size = posix_acl_xattr_size(acl->a_count);
		value = kmalloc(size, GFP_KERNEL);
		if (!value)
			return -ENOMEM;

		error = posix_acl_to_xattr(&init_user_ns, acl, value, size);
		if (error < 0)
			goto out;
	}

	gossip_debug(GOSSIP_ACL_DEBUG,
		     "%s: name %s, value %p, size %zd, acl %p\n",
		     __func__, name, value, size, acl);
	/*
	 * Go ahead and set the extended attribute now. NOTE: Suppose acl
	 * was NULL, then value will be NULL and size will be 0 and that
	 * will xlate to a removexattr. However, we don't want removexattr
	 * complain if attributes does not exist.
	 */
	error = orangefs_inode_setxattr(inode, name, value, size, 0);

out:
	kfree(value);
	if (!error)
		set_cached_acl(inode, type, acl);
	return error;
}

Vulnerability Type: +Priv 
CWE ID: CWE-285
Summary: The filesystem implementation in the Linux kernel through 4.8.2 preserves the setgid bit during a setxattr call, which allows local users to gain group privileges by leveraging the existence of a setgid program with restrictions on execute permissions.
Commit Message: posix_acl: Clear SGID bit when setting file permissions

When file permissions are modified via chmod(2) and the user is not in
the owning group or capable of CAP_FSETID, the setgid bit is cleared in
inode_change_ok().  Setting a POSIX ACL via setxattr(2) sets the file
permissions as well as the new ACL, but doesn't clear the setgid bit in
a similar way; this allows to bypass the check in chmod(2).  Fix that.

References: CVE-2016-7097
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>