From patchwork Tue Aug 15 12:50:36 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Rutland X-Patchwork-Id: 9901741 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 5432F60244 for ; Tue, 15 Aug 2017 12:52:45 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 469A025E13 for ; Tue, 15 Aug 2017 12:52:45 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 3B54D27F88; Tue, 15 Aug 2017 12:52:45 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id 6803625E13 for ; Tue, 15 Aug 2017 12:52:44 +0000 (UTC) Received: (qmail 21900 invoked by uid 550); 15 Aug 2017 12:52:42 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 21873 invoked from network); 15 Aug 2017 12:52:42 -0000 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 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> Subject: [kernel-hardening] [PATCHv2 01/14] arm64: remove __die()'s stack dump X-Virus-Scanned: ClamAV using ClamSMTP 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); }