Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933448AbeAAOro (ORCPT + 1 other); Mon, 1 Jan 2018 09:47:44 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:47052 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932963AbeAAOrl (ORCPT ); Mon, 1 Jan 2018 09:47:41 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Mathieu Desnoyers , Thomas Gleixner , Andy Lutomirski , Borislav Petkov , Dave Hansen , Dominik Brodowski , Linus Torvalds , Linus Torvalds , Peter Zijlstra , Ingo Molnar Subject: [PATCH 4.14 143/146] x86/ldt: Plug memory leak in error path Date: Mon, 1 Jan 2018 15:38:54 +0100 Message-Id: <20180101140144.414435784@linuxfoundation.org> X-Mailer: git-send-email 2.15.1 In-Reply-To: <20180101140123.743014891@linuxfoundation.org> References: <20180101140123.743014891@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Thomas Gleixner commit a62d69857aab4caa43049e72fe0ed5c4a60518dd upstream. The error path in write_ldt() tries to free 'old_ldt' instead of the newly allocated 'new_ldt', resulting in a memory leak. It also misses to clean up a half populated LDT pagetable, which is not a leak as it gets cleaned up when the process exits. Free both the potentially half populated LDT pagetable and the newly allocated LDT struct. This can be done unconditionally because once an LDT is mapped subsequent maps will succeed, because the PTE page is already populated and the two LDTs fit into that single page. Reported-by: Mathieu Desnoyers Signed-off-by: Thomas Gleixner Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Dave Hansen Cc: Dominik Brodowski Cc: Linus Torvalds Cc: Linus Torvalds Cc: Peter Zijlstra Fixes: f55f0501cbf6 ("x86/pti: Put the LDT in its own PGD if PTI is on") Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1712311121340.1899@nanos Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/ldt.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) --- a/arch/x86/kernel/ldt.c +++ b/arch/x86/kernel/ldt.c @@ -421,7 +421,13 @@ static int write_ldt(void __user *ptr, u */ error = map_ldt_struct(mm, new_ldt, old_ldt ? !old_ldt->slot : 0); if (error) { - free_ldt_struct(old_ldt); + /* + * This only can fail for the first LDT setup. If an LDT is + * already installed then the PTE page is already + * populated. Mop up a half populated page table. + */ + free_ldt_pgtables(mm); + free_ldt_struct(new_ldt); goto out_unlock; }