linux-kernel - Re: [PATCH -tip 2/2] [BUGFIX] kprobes/x86: Fix removed int3 checking order

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: <4BD856BC.1000600@redhat.com>
Date:	Wed, 28 Apr 2010 11:39:40 -0400
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	ananth@...ibm.com
CC:	Ingo Molnar <mingo@...e.hu>, lkml <linux-kernel@...r.kernel.org>,
	systemtap <systemtap@...rces.redhat.com>,
	DLE <dle-develop@...ts.sourceforge.net>,
	Dave Anderson <anderson@...hat.com>
Subject: Re: [PATCH -tip 2/2] [BUGFIX] kprobes/x86: Fix removed int3	checking
 order

Ananth N Mavinakayanahalli wrote:
> On Tue, Apr 27, 2010 at 06:33:49PM -0400, Masami Hiramatsu wrote:
>> Fix kprobe/x86 to check removed int3 when failing to get kprobe
>> from hlist. Since we have a time window between checking int3
>> exists on probed address and getting kprobe on that address,
>> we can have following senario.
>> -------
>> CPU1                     CPU2
>> hit int3
>> check int3 exists
>>                          remove int3
>>                          remove kprobe from hlist
>> get kprobe from hlist
>> no kprobe->OOPS!
>> -------
> 
> Do you have a testcase for this issue?

I heard this issue was found by systemtap team on stable kernel(means
no jump optimization). Their testsuites caused an oops (but not 100%
reproducible) with "pr10854" testcase, which registers over 5000
probes at once and removes it soon.

>> This patch moves int3 checking if there is no kprobe on that
>> address for fixing this problem as follows;
>> ------
>> CPU1                     CPU2
>> hit int3
>>                          remove int3
>>                          remove kprobe from hlist
>> get kprobe from hlist
>> no kprobe->check int3 exists
>>          ->rollback&retry
>> ------
> 
> You may also want to fix up the comment on top of kprobe_handler() about
> the interrupt gate as its only true for x86_32 and not x86_64, right?

Hmm, I couldn't find it, could you tell me more details?
(and maybe, it's another issue)

what I could find is int3 handler is registered as interrupt gate
on both of x86-32/64.

void __init trap_init(void)
{
...
        /* int3 can be called from all */
        set_system_intr_gate_ist(3, &int3, DEBUG_STACK);


> 
>> Signed-off-by: Masami Hiramatsu <mhiramat@...hat.com>
>> Cc: Ananth N Mavinakayanahalli <ananth@...ibm.com>
>> Cc: Dave Anderson <anderson@...hat.com>
>> Cc: Ingo Molnar <mingo@...e.hu>
> 
> Acked-by: Ananth N Mavinakayanahalli <ananth@...ibm.com>

Thank you,

-- 
Masami Hiramatsu
e-mail: mhiramat@...hat.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/