linux-kernel - [PATCH] x86: fix potential memleak in do_error

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Date:	Mon, 23 May 2016 15:54:28 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Aleksa Sarai <asarai@...e.de>, LKML <linux-kernel@...r.kernel.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	linux-s390@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org
Subject: [PATCH] x86: fix potential memleak in do_error_trap

And here is the x86 one. I haven't found others so far but I haven't
checked other architectures and I might have missed some callpaths for
x86 as well. Also please note this hasn't been tested properly and
it is based on the code reading.
---
>From fa8e84058c243f81a49c847624daaf935efdeb5a Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@...e.com>
Date: Mon, 23 May 2016 15:47:28 +0200
Subject: [PATCH] x86: fix potential memleak in do_error_trap

do_error_trap defines on stack siginfo structure which is then sent down
to do_trap -> force_sig_info without initializing it. __send_signal ->
copy_siginfo will copy the content for later use when the signal is
dequeued. This information might later leak into userspace. Fix it by
clearing the whole siginfo in do_error_trap before sending it to
do_trap.

Signed-off-by: Michal Hocko <mhocko@...e.com>
---
 arch/x86/kernel/traps.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index d1590486204a..945b4dfc02e6 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -271,6 +271,7 @@ static void do_error_trap(struct pt_regs *regs, long error_code, char *str,
 
 	if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) !=
 			NOTIFY_STOP) {
+		memset(&info, 0, sizeof(info));
 		cond_local_irq_enable(regs);
 		do_trap(trapnr, signr, str, regs, error_code,
 			fill_trap_info(regs, signr, trapnr, &info));
-- 
2.8.1

-- 
Michal Hocko
SUSE Labs