From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Tue, 28 Aug 2018 22:14:15 +0200 In-Reply-To: <20180828201421.157735-1-jannh@google.com> Message-Id: <20180828201421.157735-2-jannh@google.com> Mime-Version: 1.0 References: <20180828201421.157735-1-jannh@google.com> Subject: [PATCH v3 1/7] x86: refactor kprobes_fault() like kprobe_exceptions_notify() From: Jann Horn To: Kees Cook , Thomas Gleixner , Ingo Molnar , x86@kernel.org, Andy Lutomirski , kernel-hardening@lists.openwall.com, jannh@google.com Cc: linux-kernel@vger.kernel.org, dvyukov@google.com, Masami Hiramatsu , "Naveen N. Rao" , Anil S Keshavamurthy , "David S. Miller" , Alexander Viro , linux-fsdevel@vger.kernel.org, Borislav Petkov Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: This is an extension of commit b506a9d08bae ("x86: code clarification patch to Kprobes arch code"). As that commit explains, even though kprobe_running() can't be called with preemption enabled, you don't have to disable preemption - if preemption is on, you can't be in a kprobe. Also, use X86_TRAP_PF instead of 14. Signed-off-by: Jann Horn --- v3: - avoid unnecessary branch on return value and split up the checks (Borislav Petkov) arch/x86/mm/fault.c | 24 +++++++++++++----------- 1 file changed, 13 insertions(+), 11 deletions(-) diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index b9123c497e0a..bcdaae1d5bf5 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -44,17 +44,19 @@ kmmio_fault(struct pt_regs *regs, unsigned long addr) static nokprobe_inline int kprobes_fault(struct pt_regs *regs) { - int ret = 0; - - /* kprobe_running() needs smp_processor_id() */ - if (kprobes_built_in() && !user_mode(regs)) { - preempt_disable(); - if (kprobe_running() && kprobe_fault_handler(regs, 14)) - ret = 1; - preempt_enable(); - } - - return ret; + if (!kprobes_built_in()) + return 0; + if (user_mode(regs)) + return 0; + /* + * To be potentially processing a kprobe fault and to be allowed to call + * kprobe_running(), we have to be non-preemptible. + */ + if (preemptible()) + return 0; + if (!kprobe_running()) + return 0; + return kprobe_fault_handler(regs, X86_TRAP_PF); } /* -- 2.19.0.rc0.228.g281dcd1b4d0-goog