From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752370AbaHADF0 (ORCPT ); Thu, 31 Jul 2014 23:05:26 -0400 Received: from mail-pa0-f50.google.com ([209.85.220.50]:62388 "EHLO mail-pa0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750978AbaHADFZ (ORCPT ); Thu, 31 Jul 2014 23:05:25 -0400 Date: Thu, 31 Jul 2014 20:05:20 -0700 From: Omar Sandoval To: will.deacon@arm.com, linux-arm-kernel@lists.infradead.org, linux@arm.linux.org.uk, linux-kernel@vger.kernel.org, Catalin.Marinas@arm.com Subject: [PATCH] ARM: don't enter kgdb when userspace executes a kgdb break instruction. Message-ID: <20140801030520.GA27665@mew> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The kgdb breakpoint hooks (kgdb_brk_fn and kgdb_compiled_brk_fn) should only be entered when a kgdb break instruction is executed from the kernel. Otherwise, if kgdb is enabled, a userspace program can cause the kernel to drop into the debugger by executing either KGDB_BREAKINST or KGDB_COMPILED_BREAK. Signed-off-by: Omar Sandoval --- On a kernel running with kgdb enabled, this program reproduces the problem: .globl _start _start: udf #65006 @ KGDB_BREAKINST The same problem has been fixed in ARM64. arch/arm/kernel/kgdb.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/arm/kernel/kgdb.c b/arch/arm/kernel/kgdb.c index 778c2f7..a74b53c 100644 --- a/arch/arm/kernel/kgdb.c +++ b/arch/arm/kernel/kgdb.c @@ -160,12 +160,16 @@ static int kgdb_compiled_brk_fn(struct pt_regs *regs, unsigned int instr) static struct undef_hook kgdb_brkpt_hook = { .instr_mask = 0xffffffff, .instr_val = KGDB_BREAKINST, + .cpsr_mask = MODE_MASK, + .cpsr_val = SVC_MODE, .fn = kgdb_brk_fn }; static struct undef_hook kgdb_compiled_brkpt_hook = { .instr_mask = 0xffffffff, .instr_val = KGDB_COMPILED_BREAK, + .cpsr_mask = MODE_MASK, + .cpsr_val = SVC_MODE, .fn = kgdb_compiled_brk_fn }; -- 2.0.3