linux-kernel - Re: s390 && user_enable_single_step() (Was: odd utrace testing results on s390x)

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: <20100104193044.GB21146@redhat.com>
Date:	Mon, 4 Jan 2010 20:30:44 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Martin Schwidefsky <schwidefsky@...ibm.com>
Cc:	caiqian@...hat.com, Heiko Carstens <heiko.carstens@...ibm.com>,
	Jan Kratochvil <jkratoch@...hat.com>,
	Roland McGrath <roland@...hat.com>,
	linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
	utrace-devel@...hat.com
Subject: Re: s390 && user_enable_single_step() (Was: odd utrace testing
	results on s390x)

On 01/04, Oleg Nesterov wrote:
>
> IOW. I think this problem is minor and probably can be ignored,

Or may be not...

Even if the child is not killed by SIGTRAP, it can get a lot of
unnecessary traps.

To verify, I did another trivial patch (below), and the test
case from 6580807da14c423f0d0a708108e6df6ebc8bc83d does trigger
a lot of "false step" printks.

Hmm. And sometimes there is nothing in dmesg, but the test-case
needs a lot of time to complete. "taskset -c" seems to always
trigger printk's. Magic.

Oleg.

--- arch/s390/kernel/traps.c~	2009-12-22 10:41:52.909174198 -0500
+++ arch/s390/kernel/traps.c	2010-01-04 13:19:51.038187586 -0500
@@ -384,6 +384,8 @@ void __kprobes do_single_step(struct pt_
 	}
 	if (tracehook_consider_fatal_signal(current, SIGTRAP))
 		force_sig(SIGTRAP, current);
+	else
+		printk("false step\n");
 }
 
 static void default_trap_handler(struct pt_regs * regs, long interruption_code)

--
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/