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: <5762dc9e-dc9f-81ff-829e-cfa6ca2180d2@huawei.com>
Date:   Tue, 15 Nov 2022 10:01:11 +0800
From:   "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Zhang Qiang1 <qiang1.zhang@...el.com>,
        "Uladzislau Rezki (Sony)" <urezki@...il.com>
Subject: Re: [PATCH] mm/vmalloc: allow mem_dump_obj() to be called in
 interrupt context



On 2022/11/15 8:54, Andrew Morton wrote:
> On Sat, 12 Nov 2022 20:15:37 +0800 Zhen Lei <thunder.leizhen@...wei.com> wrote:
> 
>> The function mem_dump_obj() can sometimes provide valuable debugging
>> information, but it cannot be called in an interrupt context because
>> spinlock vmap_area_lock has not been protected against IRQs. If the
>> current task has held the lock before hard/soft interrupt handler calls
>> mem_dump_obj(), simply abandoning the dump operation can avoid deadlock.
>> That is, no deadlock occurs in extreme cases, and dump succeeds in most
>> cases.
>>
>> ...
>>
>> --- a/mm/vmalloc.c
>> +++ b/mm/vmalloc.c
>> @@ -4034,6 +4034,9 @@ bool vmalloc_dump_obj(void *object)
>>  	struct vm_struct *vm;
>>  	void *objp = (void *)PAGE_ALIGN((unsigned long)object);
>>  
>> +	if (unlikely(spin_is_locked(&vmap_area_lock)))
>> +		return false;
>> +
>>  	vm = find_vm_area(objp);
>>  	if (!vm)
>>  		return false;
> 
> Yes, but this will worsen the current uses of this function.  Consider
> the case where task A wants to call vmalloc_dump_obj() but task B holds
> vmap_area_lock.  No problem, task A will simply spin until task B is
> done.
> 
> But after this patch, task A's call to vmalloc_dump_obj() will return
> without having done anything.

Oh, right, this problem occurs when task A and task B run on
two different cores.


> 
> .
> 

-- 
Regards,
  Zhen Lei

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ