linux-kernel - Re: [BUG] kvm: dereference srcu-protected pointer without srcu_read

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Date:	Wed, 21 Apr 2010 11:17:22 +0300
From:	Avi Kivity <avi@...hat.com>
To:	paulmck@...ux.vnet.ibm.com
CC:	Lai Jiangshan <laijs@...fujitsu.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, kvm@...r.kernel.org
Subject: Re: [BUG] kvm: dereference srcu-protected pointer without srcu_read_lock()
 held

On 04/21/2010 01:21 AM, Paul E. McKenney wrote:
>
>> Subject: [PATCH] kvm: add missing srcu_read_lock()
>>
>> I got this dmesg due to srcu_read_lock() is missing in
>> kvm_mmu_notifier_release().
>>
>> ===================================================
>> [ INFO: suspicious rcu_dereference_check() usage. ]
>> ---------------------------------------------------
>> arch/x86/kvm/x86.h:72 invoked rcu_dereference_check() without protection!
>>
>> other info that might help us debug this:
>>
>>
>> rcu_scheduler_active = 1, debug_locks = 0
>> 2 locks held by qemu-system-x86/3100:
>>   #0:  (rcu_read_lock){.+.+..}, at: [<ffffffff810d73dc>] __mmu_notifier_release+0x38/0xdf
>>   #1:  (&(&kvm->mmu_lock)->rlock){+.+...}, at: [<ffffffffa0130a6a>] kvm_mmu_zap_all+0x21/0x5e [kvm]
>>
>> stack backtrace:
>> Pid: 3100, comm: qemu-system-x86 Not tainted 2.6.34-rc3-22949-gbc8a97a-dirty #2
>> Call Trace:
>>   [<ffffffff8106afd9>] lockdep_rcu_dereference+0xaa/0xb3
>>   [<ffffffffa0123a89>] unalias_gfn+0x56/0xab [kvm]
>>   [<ffffffffa0119600>] gfn_to_memslot+0x16/0x25 [kvm]
>>   [<ffffffffa012ffca>] gfn_to_rmap+0x17/0x6e [kvm]
>>   [<ffffffffa01300c1>] rmap_remove+0xa0/0x19d [kvm]
>>   [<ffffffffa0130649>] kvm_mmu_zap_page+0x109/0x34d [kvm]
>>   [<ffffffffa0130a7e>] kvm_mmu_zap_all+0x35/0x5e [kvm]
>>   [<ffffffffa0122870>] kvm_arch_flush_shadow+0x16/0x22 [kvm]
>>   [<ffffffffa01189e0>] kvm_mmu_notifier_release+0x15/0x17 [kvm]
>>   [<ffffffff810d742c>] __mmu_notifier_release+0x88/0xdf
>>   [<ffffffff810d73dc>] ? __mmu_notifier_release+0x38/0xdf
>>   [<ffffffff81040848>] ? exit_mm+0xe0/0x115
>>   [<ffffffff810c2cb0>] exit_mmap+0x2c/0x17e
>>   [<ffffffff8103c472>] mmput+0x2d/0xd4
>>   [<ffffffff81040870>] exit_mm+0x108/0x115
>> [...]
>>      
> Queued, thank you, Lai!
>    

Paul, I'd like to merge this via the kvm tree.

-- 
error compiling committee.c: too many arguments to function

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