Messages in this thread | | | Subject | RE: [discuss] [PATCH] utilization of kprobe_mutex is incorrect on x86_64 | Date | Fri, 30 Sep 2005 14:34:26 +0800 | From | "Zhang, Yanmin" <> |
| |
>>-----Original Message----- >>From: Andi Kleen [mailto:ak@suse.de] >>Sent: 2005年9月29日 22:31 >>To: prasanna@in.ibm.com >>Cc: Zhang, Yanmin; linux-kernel@vger.kernel.org; discuss@x86-64.org; >>systemtap@sources.redhat.com; Keshavamurthy, Anil S >>Subject: Re: [discuss] [PATCH] utilization of kprobe_mutex is incorrect on >>x86_64 >> >>On Thursday 29 September 2005 16:13, Prasanna S Panchamukhi wrote: >>> >On Thu, Sep 29, 2005 at 08:43:44AM +0800, Zhang, Yanmin wrote: >>> >> <<kprobe_incorrect_kprobe_mutex_2.6.14-rc2_x86_64.patch>> I found it >>> >> when reading the source codes. Basically, the bug could break >>> >> kprobe_insn_pages under multi-thread environment. PPC arch also has the >>> >> problem. >>> > >>> >Can you describe what the problem actually is? >>> >>> Andi, >>> >>> The up()/down() orders are incorrect in arch/x86_64/kprobes.c file while >>> trying to get/remove a kprobes instruction slot in arch_prepare_kprobe() >>> and arch_remove_kprobe() routines. Zhang's patch corrects this. >> >>What I meant is that someone should describe why they are incorrect. >>I could probably figure it out from the code, but in general the standards >>for changelogs are higher than just "bla is wrong". It should be more like >>"bla doesn't do X, so bad thing Y happens, which causes crash Z". Please >>follow this in future patches.
Andy, Sorry for lack of detailed explanation. What Prasanna said is correct. The up()/down() orders are incorrect in arch/x86_64/kprobes.c file. kprobe_mutext is used to protect the free kprobe instruction slot list. arch_prepare_kprobe applies for a slot from the free list, and arch_remove_kprobe returns a slot to the free list. The incorrect up()/down() orders to operate on kprobe_mutex fail to protect the free list. If 2 threads try to get/return kprobe instruction slot at the same time, the free slot list might be broken, or a free slot might be applied by 2 threads. My patch fixes it.
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |