From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:37044 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1031818AbeGAQj4 (ORCPT ); Sun, 1 Jul 2018 12:39:56 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Peter Zijlstra , Steven Rostedt , dvyukov@google.com, syzkaller@googlegroups.com, fengguang.wu@intel.com, Tetsuo Handa , Sergey Senozhatsky , Petr Mladek Subject: [PATCH 4.17 039/220] printk: fix possible reuse of va_list variable Date: Sun, 1 Jul 2018 18:21:03 +0200 Message-Id: <20180701160909.962246295@linuxfoundation.org> In-Reply-To: <20180701160908.272447118@linuxfoundation.org> References: <20180701160908.272447118@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.17-stable review patch. If anyone has any objections, please let me know. ------------------ From: Tetsuo Handa commit 988a35f8da1dec5a8cd2788054d1e717be61bf25 upstream. I noticed that there is a possibility that printk_safe_log_store() causes kernel oops because "args" parameter is passed to vsnprintf() again when atomic_cmpxchg() detected that we raced. Fix this by using va_copy(). Link: http://lkml.kernel.org/r/201805112002.GIF21216.OFVHFOMLJtQFSO@I-love.SAKURA.ne.jp Cc: Peter Zijlstra Cc: Steven Rostedt Cc: dvyukov@google.com Cc: syzkaller@googlegroups.com Cc: fengguang.wu@intel.com Cc: linux-kernel@vger.kernel.org Signed-off-by: Tetsuo Handa Fixes: 42a0bb3f71383b45 ("printk/nmi: generic solution for safe printk in NMI") Cc: 4.7+ # v4.7+ Reviewed-by: Sergey Senozhatsky Signed-off-by: Petr Mladek Signed-off-by: Greg Kroah-Hartman --- kernel/printk/printk_safe.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/kernel/printk/printk_safe.c +++ b/kernel/printk/printk_safe.c @@ -82,6 +82,7 @@ static __printf(2, 0) int printk_safe_lo { int add; size_t len; + va_list ap; again: len = atomic_read(&s->len); @@ -100,7 +101,9 @@ again: if (!len) smp_rmb(); - add = vscnprintf(s->buffer + len, sizeof(s->buffer) - len, fmt, args); + va_copy(ap, args); + add = vscnprintf(s->buffer + len, sizeof(s->buffer) - len, fmt, ap); + va_end(ap); if (!add) return 0;