From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932893AbdCXGw6 (ORCPT ); Fri, 24 Mar 2017 02:52:58 -0400 Received: from terminus.zytor.com ([65.50.211.136]:34143 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932331AbdCXGwp (ORCPT ); Fri, 24 Mar 2017 02:52:45 -0400 Date: Thu, 23 Mar 2017 23:45:56 -0700 From: tip-bot for Kees Cook Message-ID: Cc: hpa@zytor.com, peterz@infradead.org, keescook@chromium.org, jpoimboe@redhat.com, tglx@linutronix.de, luto@kernel.org, mingo@kernel.org, bp@alien8.de, torvalds@linux-foundation.org, dvlasenk@redhat.com, linux-kernel@vger.kernel.org, brgerst@gmail.com, robert@swiecki.net Reply-To: robert@swiecki.net, brgerst@gmail.com, dvlasenk@redhat.com, linux-kernel@vger.kernel.org, mingo@kernel.org, bp@alien8.de, torvalds@linux-foundation.org, jpoimboe@redhat.com, tglx@linutronix.de, luto@kernel.org, hpa@zytor.com, peterz@infradead.org, keescook@chromium.org In-Reply-To: <20170323224616.GA92694@beast> References: <20170323224616.GA92694@beast> To: linux-tip-commits@vger.kernel.org Subject: [tip:core/urgent] lib/syscall: Clear return values when no stack Git-Commit-ID: 854fbd6e5f60fe99e8e3a569865409fca378f143 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 854fbd6e5f60fe99e8e3a569865409fca378f143 Gitweb: http://git.kernel.org/tip/854fbd6e5f60fe99e8e3a569865409fca378f143 Author: Kees Cook AuthorDate: Thu, 23 Mar 2017 15:46:16 -0700 Committer: Ingo Molnar CommitDate: Fri, 24 Mar 2017 07:43:35 +0100 lib/syscall: Clear return values when no stack Commit: aa1f1a639621 ("lib/syscall: Pin the task stack in collect_syscall()") ... added logic to handle a process stack not existing, but left sp and pc uninitialized, which can be later reported via /proc/$pid/syscall for zombie processes, potentially exposing kernel memory to userspace. Zombie /proc/$pid/syscall before: -1 0xffffffff9a060100 0xffff92f42d6ad900 Zombie /proc/$pid/syscall after: -1 0x0 0x0 Reported-by: Robert Święcki Signed-off-by: Kees Cook Reviewed-by: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: stable@vger.kernel.org # v4.9+ Fixes: aa1f1a639621 ("lib/syscall: Pin the task stack in collect_syscall()") Link: http://lkml.kernel.org/r/20170323224616.GA92694@beast Signed-off-by: Ingo Molnar --- lib/syscall.c | 1 + 1 file changed, 1 insertion(+) diff --git a/lib/syscall.c b/lib/syscall.c index 17d5ff5..2c6cd1b 100644 --- a/lib/syscall.c +++ b/lib/syscall.c @@ -12,6 +12,7 @@ static int collect_syscall(struct task_struct *target, long *callno, if (!try_get_task_stack(target)) { /* Task has no stack, so the task isn't in a syscall. */ + *sp = *pc = 0; *callno = -1; return 0; }