linux-kernel - [PATCH] x86: Avoid intermixing cpu dump_stack output on multi-processor systems

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-next>] [day] [month] [year] [list]

Message-ID: <20120524144229.GA27713@sgi.com>
Date:	Thu, 24 May 2012 09:42:29 -0500
From:	Russ Anderson <rja@....com>
To:	linux-kernel@...r.kernel.org, x86@...nel.org
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Russ Anderson <rja@....com>
Subject: [PATCH] x86: Avoid intermixing cpu dump_stack output on multi-processor systems

When multiple cpus on a multi-processor system call dump_stack()
at the same time, the backtrace lines get intermixed, making 
the output worthless.  Add a lock so each cpu stack dump comes
out as a coherent set.

For example, when a multi-processor system is NMIed, all of the
cpus call dump_stack() at the same time, resulting in output for
all of cpus getting intermixed, making it impossible to tell what
any individual cpu was doing.  With this patch each cpu prints
its stack lines as a coherent set, so one can see what each cpu
was doing.

It has been tested on a 4069 cpu system.

Signed-off-by: Russ Anderson <rja@....com>

---
 arch/x86/kernel/dumpstack.c |    3 +++
 1 file changed, 3 insertions(+)

Index: linux/arch/x86/kernel/dumpstack.c
===================================================================
--- linux.orig/arch/x86/kernel/dumpstack.c	2012-05-03 14:31:13.602345805 -0500
+++ linux/arch/x86/kernel/dumpstack.c	2012-05-03 14:51:43.805197563 -0500
@@ -186,7 +186,9 @@ void dump_stack(void)
 {
 	unsigned long bp;
 	unsigned long stack;
+	static DEFINE_SPINLOCK(lock);	/* Serialise the printks */
 
+	spin_lock(&lock);
 	bp = stack_frame(current, NULL);
 	printk("Pid: %d, comm: %.20s %s %s %.*s\n",
 		current->pid, current->comm, print_tainted(),
@@ -194,6 +196,7 @@ void dump_stack(void)
 		(int)strcspn(init_utsname()->version, " "),
 		init_utsname()->version);
 	show_trace(NULL, NULL, &stack, bp);
+	spin_unlock(&lock);
 }
 EXPORT_SYMBOL(dump_stack);
 
-- 
Russ Anderson, OS RAS/Partitioning Project Lead  
SGI - Silicon Graphics Inc          rja@....com
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/