linux-kernel - [tip: core/rcu] printk: Disallow instrumenting print_nmi

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <158991795665.17951.2179685164369351471.tip-bot2@tip-bot2>
Date:   Tue, 19 May 2020 19:52:36 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        x86 <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: [tip: core/rcu] printk: Disallow instrumenting print_nmi_enter()

The following commit has been merged into the core/rcu branch of tip:

Commit-ID:     b0f51883f551b900a04a80f49fb0886caf7e9a12
Gitweb:        https://git.kernel.org/tip/b0f51883f551b900a04a80f49fb0886caf7e9a12
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Mon, 24 Feb 2020 22:25:03 +01:00
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Tue, 19 May 2020 15:51:16 +02:00

printk: Disallow instrumenting print_nmi_enter()

It happens early in nmi_enter(), no tracing, probing or other funnies
allowed. Specifically as nmi_enter() will be used in do_debug(), which
would cause recursive exceptions when kprobed.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@...cle.com>
Link: https://lkml.kernel.org/r/20200505134101.139720912@linutronix.de


---
 kernel/printk/printk_safe.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c
index e8791f2..4242403 100644
--- a/kernel/printk/printk_safe.c
+++ b/kernel/printk/printk_safe.c
@@ -10,6 +10,7 @@
 #include <linux/cpumask.h>
 #include <linux/irq_work.h>
 #include <linux/printk.h>
+#include <linux/kprobes.h>
 
 #include "internal.h"
 
@@ -293,12 +294,12 @@ static __printf(1, 0) int vprintk_nmi(const char *fmt, va_list args)
 	return printk_safe_log_store(s, fmt, args);
 }
 
-void notrace printk_nmi_enter(void)
+void noinstr printk_nmi_enter(void)
 {
 	this_cpu_add(printk_context, PRINTK_NMI_CONTEXT_OFFSET);
 }
 
-void notrace printk_nmi_exit(void)
+void noinstr printk_nmi_exit(void)
 {
 	this_cpu_sub(printk_context, PRINTK_NMI_CONTEXT_OFFSET);
 }