From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933932AbdA0Lgd (ORCPT ); Fri, 27 Jan 2017 06:36:33 -0500 Received: from mx2.suse.de ([195.135.220.15]:36796 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933730AbdA0LNA (ORCPT ); Fri, 27 Jan 2017 06:13:00 -0500 X-Amavis-Alert: BAD HEADER SECTION, Duplicate header field: "References" From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Mark Rutland , Will Deacon , Catalin Marinas , Jiri Slaby Subject: [PATCH 3.12 172/235] arm64: avoid returning from bad_mode Date: Fri, 27 Jan 2017 11:55:05 +0100 Message-Id: X-Mailer: git-send-email 2.11.0 In-Reply-To: <5b46dc789ca2be4046e4e40a131858d386cac741.1485514374.git.jslaby@suse.cz> References: <5b46dc789ca2be4046e4e40a131858d386cac741.1485514374.git.jslaby@suse.cz> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Mark Rutland 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit 7d9e8f71b989230bc613d121ca38507d34ada849 upstream. Generally, taking an unexpected exception should be a fatal event, and bad_mode is intended to cater for this. However, it should be possible to contain unexpected synchronous exceptions from EL0 without bringing the kernel down, by sending a SIGILL to the task. We tried to apply this approach in commit 9955ac47f4ba1c95 ("arm64: don't kill the kernel on a bad esr from el0"), by sending a signal for any bad_mode call resulting from an EL0 exception. However, this also applies to other unexpected exceptions, such as SError and FIQ. The entry paths for these exceptions branch to bad_mode without configuring the link register, and have no kernel_exit. Thus, if we take one of these exceptions from EL0, bad_mode will eventually return to the original user link register value. This patch fixes this by introducing a new bad_el0_sync handler to cater for the recoverable case, and restoring bad_mode to its original state, whereby it calls panic() and never returns. The recoverable case branches to bad_el0_sync with a bl, and returns to userspace via the usual ret_to_user mechanism. Signed-off-by: Mark Rutland Fixes: 9955ac47f4ba1c95 ("arm64: don't kill the kernel on a bad esr from el0") Reported-by: Mark Salter Cc: Will Deacon Signed-off-by: Catalin Marinas Signed-off-by: Jiri Slaby --- arch/arm64/kernel/entry.S | 2 +- arch/arm64/kernel/traps.c | 25 +++++++++++++++++++++---- 2 files changed, 22 insertions(+), 5 deletions(-) diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 028a1b91e2b3..c405e2421fd8 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -493,7 +493,7 @@ el0_inv: mov x0, sp mov x1, #BAD_SYNC mrs x2, esr_el1 - b bad_mode + b bad_el0_sync ENDPROC(el0_sync) .align 6 diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index 7ffadddb645d..7d1f6c5cfa65 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -306,16 +306,33 @@ asmlinkage long do_ni_syscall(struct pt_regs *regs) } /* - * bad_mode handles the impossible case in the exception vector. + * bad_mode handles the impossible case in the exception vector. This is always + * fatal. */ asmlinkage void bad_mode(struct pt_regs *regs, int reason, unsigned int esr) { - siginfo_t info; - void __user *pc = (void __user *)instruction_pointer(regs); console_verbose(); pr_crit("Bad mode in %s handler detected, code 0x%08x\n", handler[reason], esr); + + die("Oops - bad mode", regs, 0); + local_irq_disable(); + panic("bad mode"); +} + +/* + * bad_el0_sync handles unexpected, but potentially recoverable synchronous + * exceptions taken from EL0. Unlike bad_mode, this returns. + */ +asmlinkage void bad_el0_sync(struct pt_regs *regs, int reason, unsigned int esr) +{ + siginfo_t info; + void __user *pc = (void __user *)instruction_pointer(regs); + console_verbose(); + + pr_crit("Bad EL0 synchronous exception detected on CPU%d, code 0x%08x\n", + smp_processor_id(), esr); __show_regs(regs); info.si_signo = SIGILL; @@ -323,7 +340,7 @@ asmlinkage void bad_mode(struct pt_regs *regs, int reason, unsigned int esr) info.si_code = ILL_ILLOPC; info.si_addr = pc; - arm64_notify_die("Oops - bad mode", regs, &info, 0); + force_sig_info(info.si_signo, &info, current); } void __pte_error(const char *file, int line, unsigned long val) -- 2.11.0