From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Lutomirski Subject: [PATCH v4 14/29] x86/dumpstack/64: Handle faults when printing the "Stack:" part of an OOPS Date: Sun, 26 Jun 2016 14:55:36 -0700 Message-ID: <32fe31a107013565b4198bb31a7e36e725e68d6f.1466974736.git.luto@kernel.org> References: Return-path: Received: from mail.kernel.org ([198.145.29.136]:59968 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751758AbcFZV4Q (ORCPT ); Sun, 26 Jun 2016 17:56:16 -0400 In-Reply-To: In-Reply-To: References: Sender: linux-arch-owner@vger.kernel.org List-ID: To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, Borislav Petkov , Nadav Amit , Kees Cook , Brian Gerst , "kernel-hardening@lists.openwall.com" , Linus Torvalds , Josh Poimboeuf , Jann Horn , Heiko Carstens , Andy Lutomirski If we overflow the stack into a guard page, we'll recursively fault when trying to dump the contents of the guard page. Use probe_kernel_address so we can recover if this happens. Reviewed-by: Josh Poimboeuf Signed-off-by: Andy Lutomirski --- arch/x86/kernel/dumpstack_64.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c index a81e1ef73bf2..6dede08dd98b 100644 --- a/arch/x86/kernel/dumpstack_64.c +++ b/arch/x86/kernel/dumpstack_64.c @@ -274,6 +274,8 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs, stack = sp; for (i = 0; i < kstack_depth_to_print; i++) { + unsigned long word; + if (stack >= irq_stack && stack <= irq_stack_end) { if (stack == irq_stack_end) { stack = (unsigned long *) (irq_stack_end[-1]); @@ -283,12 +285,18 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs, if (kstack_end(stack)) break; } + + if (probe_kernel_address(stack, word)) + break; + if ((i % STACKSLOTS_PER_LINE) == 0) { if (i != 0) pr_cont("\n"); - printk("%s %016lx", log_lvl, *stack++); + printk("%s %016lx", log_lvl, word); } else - pr_cont(" %016lx", *stack++); + pr_cont(" %016lx", word); + + stack++; touch_nmi_watchdog(); } preempt_enable(); -- 2.7.4