From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AIpwx4/o/p7MRZz76a7aqrcQltpOLgyVEc+lImifKJ3Smd4pgoXQxh6buOSY5XZY8BnDxxXAyVt9 ARC-Seal: i=1; a=rsa-sha256; t=1522168363; cv=none; d=google.com; s=arc-20160816; b=OGFm/ohD/Xvn5veA7j3U2JaWgja+q58RKdcmerZQ6WFTVJWxs0zq50+d8mYChrCObF 9ndAosg7mRVhIORrFQYCBOa/mKwy0ucmxLKPgVdLw5O5kad4jH/LFVfBQSqnzIdAa53c 9qJIZEIL8MFsoD5ZOSLkzN08wXAPFnkQAUlMJeCpiUWchZZu9c6X9jtsyw2Y9fpaGnpD kDuummmrYRr7knbQKDDUzNB/I+oW/4APMousqsGhRbgebsCsJtdbmVphY/ZaSH8Mj5rD eY7S86IdKt4KXjK5IQ6l+94BvrQsHATQMap0lkWGprY6vM+Dsoy0QyOgwYN2Ph01/bjB Y1KA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:arc-authentication-results; bh=CvYXXS37PYL8I1FVpLSKIgElGYcM+C80aNBehCp43iM=; b=iVmhotjphbtWDaIsNvGrMJzG/sTB2Z7uhaSrXLg9nyqj9BBZ8DgCh1K+p0ujXnR92r bSvYcQgcz450Zi7yTes/w/GZPY5nuJeswNVe9s5FfMR8zHCXHCG9v0GvwZwqexvvnlqr dCwo46WRZRzkhqriRVuyZT0CPW04puj/jcir0KtOqMtMSyVfWlMDjdxCnFDq3KV5gD+H cxRfw3+N9xy/YGhmP5LVyw4QH0cV4xIzXCTuhFkuPUDToxZjDHyb7j4ib4BrgKKpvdYl i6wXyNNiVcS2kJCsxcamcTQkyT7tRgnnIhcEXHf52tLhzN+rb6dWGy5Ny+1+wp3ik9XM 2Kgg== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.61.202 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.61.202 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Andy Lutomirski , Linus Torvalds , Thomas Gleixner Subject: [PATCH 4.9 53/67] x86/entry/64: Dont use IST entry for #BP stack Date: Tue, 27 Mar 2018 18:27:45 +0200 Message-Id: <20180327162730.431033236@linuxfoundation.org> X-Mailer: git-send-email 2.16.3 In-Reply-To: <20180327162726.702411083@linuxfoundation.org> References: <20180327162726.702411083@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1596109065580803384?= X-GMAIL-MSGID: =?utf-8?q?1596109213918809131?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Andy Lutomirski commit d8ba61ba58c88d5207c1ba2f7d9a2280e7d03be9 upstream. There's nothing IST-worthy about #BP/int3. We don't allow kprobes in the small handful of places in the kernel that run at CPL0 with an invalid stack, and 32-bit kernels have used normal interrupt gates for #BP forever. Furthermore, we don't allow kprobes in places that have usergs while in kernel mode, so "paranoid" is also unnecessary. Signed-off-by: Andy Lutomirski Signed-off-by: Linus Torvalds Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman --- arch/x86/entry/entry_64.S | 2 +- arch/x86/kernel/traps.c | 24 +++++++++++------------- 2 files changed, 12 insertions(+), 14 deletions(-) --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -943,7 +943,7 @@ apicinterrupt3 HYPERVISOR_CALLBACK_VECTO #endif /* CONFIG_HYPERV */ idtentry debug do_debug has_error_code=0 paranoid=1 shift_ist=DEBUG_STACK -idtentry int3 do_int3 has_error_code=0 paranoid=1 shift_ist=DEBUG_STACK +idtentry int3 do_int3 has_error_code=0 idtentry stack_segment do_stack_segment has_error_code=1 #ifdef CONFIG_XEN --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -526,7 +526,6 @@ do_general_protection(struct pt_regs *re } NOKPROBE_SYMBOL(do_general_protection); -/* May run on IST stack. */ dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code) { #ifdef CONFIG_DYNAMIC_FTRACE @@ -541,7 +540,15 @@ dotraplinkage void notrace do_int3(struc if (poke_int3_handler(regs)) return; + /* + * Use ist_enter despite the fact that we don't use an IST stack. + * We can be called from a kprobe in non-CONTEXT_KERNEL kernel + * mode or even during context tracking state changes. + * + * This means that we can't schedule. That's okay. + */ ist_enter(regs); + RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); #ifdef CONFIG_KGDB_LOW_LEVEL_TRAP if (kgdb_ll_trap(DIE_INT3, "int3", regs, error_code, X86_TRAP_BP, @@ -558,17 +565,11 @@ dotraplinkage void notrace do_int3(struc SIGTRAP) == NOTIFY_STOP) goto exit; - /* - * Let others (NMI) know that the debug stack is in use - * as we may switch to the interrupt stack. - */ - debug_stack_usage_inc(); preempt_disable(); cond_local_irq_enable(regs); do_trap(X86_TRAP_BP, SIGTRAP, "int3", regs, error_code, NULL); cond_local_irq_disable(regs); preempt_enable_no_resched(); - debug_stack_usage_dec(); exit: ist_exit(regs); } @@ -989,19 +990,16 @@ void __init trap_init(void) cpu_init(); /* - * X86_TRAP_DB and X86_TRAP_BP have been set - * in early_trap_init(). However, ITS works only after - * cpu_init() loads TSS. See comments in early_trap_init(). + * X86_TRAP_DB was installed in early_trap_init(). However, + * IST works only after cpu_init() loads TSS. See comments + * in early_trap_init(). */ set_intr_gate_ist(X86_TRAP_DB, &debug, DEBUG_STACK); - /* int3 can be called from all */ - set_system_intr_gate_ist(X86_TRAP_BP, &int3, DEBUG_STACK); x86_init.irqs.trap_init(); #ifdef CONFIG_X86_64 memcpy(&debug_idt_table, &idt_table, IDT_ENTRIES * 16); set_nmi_gate(X86_TRAP_DB, &debug); - set_nmi_gate(X86_TRAP_BP, &int3); #endif }