From patchwork Thu Jun 21 11:54:40 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Will Deacon X-Patchwork-Id: 139522 Delivered-To: patch@linaro.org Received: by 2002:a2e:970d:0:0:0:0:0 with SMTP id r13-v6csp1968759lji; Thu, 21 Jun 2018 04:54:08 -0700 (PDT) X-Google-Smtp-Source: ADUXVKKraqt77NHcSqD4VJyNBKcVk0ERlaaTtRUkzHuR2cXoL5EX9h0kvdNmuoPMGSuZKhO8DoCp X-Received: by 2002:a65:4a04:: with SMTP id s4-v6mr22132221pgq.376.1529582048643; Thu, 21 Jun 2018 04:54:08 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1529582048; cv=none; d=google.com; s=arc-20160816; b=gpUoBtJPw0gwvmUIjx6CWoU8GH5S/Pw/MSZCs4n6XROgefD8w1qDidfsF4dye3rLrd u7qc943G7ZuydSFKwxlDK6PCeuiQUUi0ayWpC08eQirQgA7PX3WQaNvA5M8vjy6MhbZ6 K6P1VRJAgoDDvlxF0c708yZ2ERhKul6S3hZrjdZARTwQfYdsbE9t/7CRdTBQltaFMcmE aUBtaS20zIGyaQJT1d2CjuI9OdGupdO4LTlUZUheJRGUY5//4eGUNSHAFjndknB4fGeS 6YJPFIKAH5VftXBZeEaznoJW794aFZIKrM/hCLnfuJxhmW/3tEJeQkxnMfet52YOA0yf B7pQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:message-id:date:subject:cc:to:from :arc-authentication-results; bh=MOwOYzLzDfNFhwS2bR2FOv9ShnpijfDf81a7mN83Kpk=; b=uXxC5JhfPV8n2GBkMhm9+fKB678LlxZ52M1TU93a0hppB+dD/2H5LRr2hVTZFXSDBZ Ar6ZGx6DH9eSXPgIn1NUX5vxFlp60KZQQs2HWYR5vhzWtkREnFL9hQcR3X0LL3wzO4pq xHLoDNNdb9iCIoAmAGzALugmK84r3evwzJNZuKrCfsDHHhL2lhffFjOKmyWGsmTBIyOy KNhb57l7UJUbkrd9+XqXXgaHUObqx22Gw2XYyAhhbU3A+e5SDjGWxB16RFnfZblN3o2K bi1X/ywMTprWNp+qPX/A4aotBVRMJOQEeoGQ3E26iVBfBTAo7Lhg/lTI8O2mV9+fcryx nDpQ== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id k124-v6si3729603pgc.519.2018.06.21.04.54.08; Thu, 21 Jun 2018 04:54:08 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933375AbeFULyG (ORCPT + 30 others); Thu, 21 Jun 2018 07:54:06 -0400 Received: from foss.arm.com ([217.140.101.70]:48958 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933130AbeFULyF (ORCPT ); Thu, 21 Jun 2018 07:54:05 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 2F5881435; Thu, 21 Jun 2018 04:54:05 -0700 (PDT) Received: from edgewater-inn.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 004E43F578; Thu, 21 Jun 2018 04:54:05 -0700 (PDT) Received: by edgewater-inn.cambridge.arm.com (Postfix, from userid 1000) id 24CFB1AE2E48; Thu, 21 Jun 2018 12:54:41 +0100 (BST) From: Will Deacon To: linux-kernel@vger.kernel.org, mathieu.desnoyers@efficios.com Cc: peterz@infradead.org, paulmck@linux.vnet.ibm.com, boqun.feng@gmail.com, mingo@redhat.com, Will Deacon Subject: [PATCH v2] rseq: Avoid infinite recursion when delivering SIGSEGV Date: Thu, 21 Jun 2018 12:54:40 +0100 Message-Id: <1529582080-31430-1-git-send-email-will.deacon@arm.com> X-Mailer: git-send-email 2.1.4 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When delivering a signal to a task that is using rseq, we call into __rseq_handle_notify_resume() so that the registers pushed in the sigframe are updated to reflect the state of the restartable sequence (for example, ensuring that the signal returns to the abort handler if necessary). However, if the rseq management fails due to an unrecoverable fault when accessing userspace or certain combinations of RSEQ_CS_* flags, then we will attempt to deliver a SIGSEGV. This has the potential for infinite recursion if the rseq code continuously fails on signal delivery. Avoid this problem by using force_sigsegv() instead of force_sig(), which is explicitly designed to reset the SEGV handler to SIG_DFL in the case of a recursive fault. In doing so, remove rseq_signal_deliver() from the internal rseq API and have an optional struct ksignal * parameter to rseq_handle_notify_resume() instead. Signed-off-by: Will Deacon --- RFC v1 -> v2: Kill rseq_signal_deliver() arch/arm/kernel/signal.c | 4 ++-- arch/powerpc/kernel/signal.c | 4 ++-- arch/x86/entry/common.c | 2 +- arch/x86/kernel/signal.c | 2 +- include/linux/sched.h | 27 ++++++++++++--------------- kernel/rseq.c | 7 ++++--- 6 files changed, 22 insertions(+), 24 deletions(-) -- 2.1.4 diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c index f09e9d66d605..184f69dcb9f2 100644 --- a/arch/arm/kernel/signal.c +++ b/arch/arm/kernel/signal.c @@ -544,7 +544,7 @@ static void handle_signal(struct ksignal *ksig, struct pt_regs *regs) * Increment event counter and perform fixup for the pre-signal * frame. */ - rseq_signal_deliver(regs); + rseq_handle_notify_resume(ksig, regs); /* * Set up the stack frame @@ -666,7 +666,7 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall) } else { clear_thread_flag(TIF_NOTIFY_RESUME); tracehook_notify_resume(regs); - rseq_handle_notify_resume(regs); + rseq_handle_notify_resume(NULL, regs); } } local_irq_disable(); diff --git a/arch/powerpc/kernel/signal.c b/arch/powerpc/kernel/signal.c index 17fe4339ba59..88bdf243a5bd 100644 --- a/arch/powerpc/kernel/signal.c +++ b/arch/powerpc/kernel/signal.c @@ -134,7 +134,7 @@ static void do_signal(struct task_struct *tsk) /* Re-enable the breakpoints for the signal stack */ thread_change_pc(tsk, tsk->thread.regs); - rseq_signal_deliver(tsk->thread.regs); + rseq_handle_notify_resume(&ksig, tsk->thread.regs); if (is32) { if (ksig.ka.sa.sa_flags & SA_SIGINFO) @@ -170,7 +170,7 @@ void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags) if (thread_info_flags & _TIF_NOTIFY_RESUME) { clear_thread_flag(TIF_NOTIFY_RESUME); tracehook_notify_resume(regs); - rseq_handle_notify_resume(regs); + rseq_handle_notify_resume(NULL, regs); } user_enter(); diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index 92190879b228..3b2490b81918 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -164,7 +164,7 @@ static void exit_to_usermode_loop(struct pt_regs *regs, u32 cached_flags) if (cached_flags & _TIF_NOTIFY_RESUME) { clear_thread_flag(TIF_NOTIFY_RESUME); tracehook_notify_resume(regs); - rseq_handle_notify_resume(regs); + rseq_handle_notify_resume(NULL, regs); } if (cached_flags & _TIF_USER_RETURN_NOTIFY) diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c index 445ca11ff863..8affeeb74935 100644 --- a/arch/x86/kernel/signal.c +++ b/arch/x86/kernel/signal.c @@ -692,7 +692,7 @@ setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs) * Increment event counter and perform fixup for the pre-signal * frame. */ - rseq_signal_deliver(regs); + rseq_handle_notify_resume(ksig, regs); /* Set up the stack frame */ if (is_ia32_frame(ksig)) { diff --git a/include/linux/sched.h b/include/linux/sched.h index 87bf02d93a27..fd23a540cd8d 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1799,20 +1799,19 @@ static inline void rseq_set_notify_resume(struct task_struct *t) set_tsk_thread_flag(t, TIF_NOTIFY_RESUME); } -void __rseq_handle_notify_resume(struct pt_regs *regs); +void __rseq_handle_notify_resume(struct ksignal *sig, struct pt_regs *regs); -static inline void rseq_handle_notify_resume(struct pt_regs *regs) +static inline void rseq_handle_notify_resume(struct ksignal *ksig, + struct pt_regs *regs) { - if (current->rseq) - __rseq_handle_notify_resume(regs); -} + if (ksig) { + preempt_disable(); + __set_bit(RSEQ_EVENT_SIGNAL_BIT, ¤t->rseq_event_mask); + preempt_enable(); + } -static inline void rseq_signal_deliver(struct pt_regs *regs) -{ - preempt_disable(); - __set_bit(RSEQ_EVENT_SIGNAL_BIT, ¤t->rseq_event_mask); - preempt_enable(); - rseq_handle_notify_resume(regs); + if (current->rseq) + __rseq_handle_notify_resume(ksig, regs); } /* rseq_preempt() requires preemption to be disabled. */ @@ -1864,10 +1863,8 @@ static inline void rseq_execve(struct task_struct *t) static inline void rseq_set_notify_resume(struct task_struct *t) { } -static inline void rseq_handle_notify_resume(struct pt_regs *regs) -{ -} -static inline void rseq_signal_deliver(struct pt_regs *regs) +static inline void rseq_handle_notify_resume(struct ksignal *ksig, + struct pt_regs *regs) { } static inline void rseq_preempt(struct task_struct *t) diff --git a/kernel/rseq.c b/kernel/rseq.c index ae306f90c514..22b6acf1ad63 100644 --- a/kernel/rseq.c +++ b/kernel/rseq.c @@ -251,10 +251,10 @@ static int rseq_ip_fixup(struct pt_regs *regs) * respect to other threads scheduled on the same CPU, and with respect * to signal handlers. */ -void __rseq_handle_notify_resume(struct pt_regs *regs) +void __rseq_handle_notify_resume(struct ksignal *ksig, struct pt_regs *regs) { struct task_struct *t = current; - int ret; + int ret, sig; if (unlikely(t->flags & PF_EXITING)) return; @@ -268,7 +268,8 @@ void __rseq_handle_notify_resume(struct pt_regs *regs) return; error: - force_sig(SIGSEGV, t); + sig = ksig ? ksig->sig : 0; + force_sigsegv(sig, t); } #ifdef CONFIG_DEBUG_RSEQ