Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752662AbdHOMwc (ORCPT ); Tue, 15 Aug 2017 08:52:32 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:51390 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752632AbdHOMwb (ORCPT ); Tue, 15 Aug 2017 08:52:31 -0400 From: Mark Rutland To: linux-arm-kernel@lists.infradead.org Cc: ard.biesheuvel@linaro.org, catalin.marinas@arm.com, james.morse@arm.com, labbott@redhat.com, linux-kernel@vger.kernel.org, luto@amacapital.net, mark.rutland@arm.com, matt@codeblueprint.co.uk, will.deacon@arm.com, kernel-hardening@lists.openwall.com, keescook@chromium.org Subject: [PATCHv2 01/14] arm64: remove __die()'s stack dump Date: Tue, 15 Aug 2017 13:50:36 +0100 Message-Id: <1502801449-29246-2-git-send-email-mark.rutland@arm.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1502801449-29246-1-git-send-email-mark.rutland@arm.com> References: <1502801449-29246-1-git-send-email-mark.rutland@arm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1621 Lines: 42 Our __die() implementation tries to dump the stack memory, in addition to a backtrace, which is problematic. For contemporary 16K stacks, this can be a lot of data, which can take a long time to dump, and can push other useful context out of the kernel's printk ringbuffer (and/or a user's scrollback buffer on an attached console). Additionally, the code implicitly assumes that the SP is on the task's stack, and tries to dump everything between the SP and the highest task stack address. When the SP points at an IRQ stack (or is corrupted), this makes the kernel attempt to dump vast amounts of VA space. With vmap'd stacks, this may result in erroneous accesses to peripherals. This patch removes the memory dump, leaving us to rely on the backtrace, and other means of dumping stack memory such as kdump. Signed-off-by: Mark Rutland Cc: Ard Biesheuvel Cc: Catalin Marinas Cc: Laura Abbott Cc: James Morse Cc: Will Deacon --- arch/arm64/kernel/traps.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index c2a81bf..9633773 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -237,8 +237,6 @@ static int __die(const char *str, int err, struct pt_regs *regs) end_of_stack(tsk)); if (!user_mode(regs)) { - dump_mem(KERN_EMERG, "Stack: ", regs->sp, - THREAD_SIZE + (unsigned long)task_stack_page(tsk)); dump_backtrace(regs, tsk); dump_instr(KERN_EMERG, regs); } -- 1.9.1