linux-kernel - [PATCH 3.11 35/93] ARM: 8064/1: fix v7-M signal return

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1403528592-2163-36-git-send-email-luis.henriques@canonical.com>
Date:	Mon, 23 Jun 2014 14:02:14 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Rabin Vincent <rabin@....in>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.11 35/93] ARM: 8064/1: fix v7-M signal return

3.11.10.12 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Rabin Vincent <rabin@....in>

commit 483a6c9d447f625b991fa04a1530493d893984db upstream.

According to the ARM ARM, the behaviour is UNPREDICTABLE if the PC read
from the exception return stack is not half word aligned.  See the
pseudo code for ExceptionReturn() and PopStack().

The signal handler's address has the bit 0 set, and setup_return()
directly writes this to regs->ARM_pc.  Current hardware happens to
discard this bit, but QEMU's emulation doesn't and this makes processes
crash.  Mask out bit 0 before the exception return in order to get
predictable behaviour.

Fixes: 19c4d593f0b4 ("ARM: ARMv7-M: Add support for exception handling")

Acked-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Signed-off-by: Rabin Vincent <rabin@....in>
Signed-off-by: Russell King <rmk+kernel@....linux.org.uk>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 arch/arm/kernel/entry-header.S | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm/kernel/entry-header.S b/arch/arm/kernel/entry-header.S
index de23a9beed13..b527a79f73f1 100644
--- a/arch/arm/kernel/entry-header.S
+++ b/arch/arm/kernel/entry-header.S
@@ -132,6 +132,10 @@
 	orrne	r5, V7M_xPSR_FRAMEPTRALIGN
 	biceq	r5, V7M_xPSR_FRAMEPTRALIGN
 
+	@ ensure bit 0 is cleared in the PC, otherwise behaviour is
+	@ unpredictable
+	bic	r4, #1
+
 	@ write basic exception frame
 	stmdb	r2!, {r1, r3-r5}
 	ldmia	sp, {r1, r3-r5}
-- 
1.9.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/