From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AIpwx49xP8/3wN9/3ub3QLKFKGXTzEy5BOctRBdcie9wiPdXB39V575TOCWeY4L4+5EgkthS/rXT ARC-Seal: i=1; a=rsa-sha256; t=1522168928; cv=none; d=google.com; s=arc-20160816; b=ZNL39fdld+CrIkSbwmpBHLde5YY4IUxE8yySWtgWQBaKlYcwwRNxdSC84eCmXvMh4+ fpKTYIUunz2gJ0y7iGlhQerd+hzwEHeS4/umIq8KQDpf2oqx38yrMcb6rNZLMMGjVIIJ Zu43xSIbFmRnYluO1FTU/oH3yHA7+PKLKh5kPs0IjeQ2tdzRU9a0wSF26M5CeKNon0R/ K9CKaqmBb7Y4qr8Ic1ynnvCsquNo9kr5cOJDiHqxeEFajrw8MYTpcu/9jda2Zz3KAswU +kkjscWuEUwfHljB9CcIyTsrPrg/SNuE13kT4Ew19gV2WF+An2aYIfAP6yhC7k0Lpfl6 Lc2Q== 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=XGfvYn3FMQBROmQa0/xHoZprINvgmBNcBVp+54Qe2nA=; b=ati3u6NKzihxxYjvF/BZHSK9HMDtPCs8EqRnCbyTtkp3CTvHks7MUxR4Zx6Yq8tmPC Z1BsdDKyqFJzQuw8r8L7WrmRJE1F5cF8JbBG7Qaj/vr1n+ylXvcPEDP3KzvEbh/3YKpX 5rKgABP7pXJ2Oj3pQPs6+UF02awwm0z5EvQE+9qKLsFcVWHduOqk3hFr9r8YN46zKoHE CjKYC7hVkRh+srZbGgJCR3pf9Yx1hJrxhwpOQR5W9S9ggZtVlZKt3iQL0ESFrlSazp0U /aC979mGIEFR2zGzKsH36PlBu7BRS9pW/W6hgfsfHNQAAzAv9Wpoofl/QLCjyz8qLH/q w4eQ== 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 4.15 083/105] x86/entry/64: Dont use IST entry for #BP stack Date: Tue, 27 Mar 2018 18:28:03 +0200 Message-Id: <20180327162803.396185242@linuxfoundation.org> X-Mailer: git-send-email 2.16.3 In-Reply-To: <20180327162757.813009222@linuxfoundation.org> References: <20180327162757.813009222@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?1596109806142627102?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.15-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/idt.c | 2 -- arch/x86/kernel/traps.c | 15 ++++++++------- 3 files changed, 9 insertions(+), 10 deletions(-) --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -1097,7 +1097,7 @@ 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/idt.c +++ b/arch/x86/kernel/idt.c @@ -160,7 +160,6 @@ static const __initconst struct idt_data */ static const __initconst struct idt_data dbg_idts[] = { INTG(X86_TRAP_DB, debug), - INTG(X86_TRAP_BP, int3), }; #endif @@ -183,7 +182,6 @@ gate_desc debug_idt_table[IDT_ENTRIES] _ static const __initconst struct idt_data ist_idts[] = { ISTG(X86_TRAP_DB, debug, DEBUG_STACK), ISTG(X86_TRAP_NMI, nmi, NMI_STACK), - SISTG(X86_TRAP_BP, int3, DEBUG_STACK), ISTG(X86_TRAP_DF, double_fault, DOUBLEFAULT_STACK), #ifdef CONFIG_X86_MCE ISTG(X86_TRAP_MC, &machine_check, MCE_STACK), --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -577,7 +577,6 @@ 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 @@ -592,6 +591,13 @@ 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 @@ -609,15 +615,10 @@ 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(); cond_local_irq_enable(regs); do_trap(X86_TRAP_BP, SIGTRAP, "int3", regs, error_code, NULL); cond_local_irq_disable(regs); - debug_stack_usage_dec(); + exit: ist_exit(regs); }