linux-kernel - Re: [PATCH v2] block: fix ioc leak in put_io

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Date:	Tue, 13 Mar 2012 15:40:17 +0100
From:	Jens Axboe <axboe@...nel.dk>
To:	Vivek Goyal <vgoyal@...hat.com>
CC:	Xiaotian Feng <xtfeng@...il.com>, tj@...nel.org,
	linux-kernel@...r.kernel.org, Xiaotian Feng <dannyfeng@...cent.com>
Subject: Re: [PATCH v2] block: fix ioc leak in put_io_context

On 03/13/2012 03:28 PM, Vivek Goyal wrote:
> On Tue, Mar 13, 2012 at 01:21:06PM -0400, Xiaotian Feng wrote:
>>     When put_io_context is called, if ioc->icq_list is empty and refcount
>>     is 1, kernel will not free the ioc.
>>
>>     This is caught by following kmemleak:
>>
>>     unreferenced object 0xffff880036349fe0 (size 216):
>>       comm "sh", pid 2137, jiffies 4294931140 (age 290579.412s)
>>       hex dump (first 32 bytes):
>>         00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>>         01 00 01 00 ad 4e ad de ff ff ff ff 00 00 00 00  .....N..........
>>       backtrace:
>>         [<ffffffff8169f926>] kmemleak_alloc+0x26/0x50
>>         [<ffffffff81195a9c>] kmem_cache_alloc_node+0x1cc/0x2a0
>>         [<ffffffff81356b67>] create_io_context_slowpath+0x27/0x130
>>         [<ffffffff81356d2b>] get_task_io_context+0xbb/0xf0
>>         [<ffffffff81055f0e>] copy_process+0x188e/0x18b0
>>         [<ffffffff8105609b>] do_fork+0x11b/0x420
>>         [<ffffffff810247f8>] sys_clone+0x28/0x30
>>         [<ffffffff816d3373>] stub_clone+0x13/0x20
>>         [<ffffffffffffffff>] 0xffffffffffffffff
>>
>>     ioc should be freed if ioc->icq_list is empty.
>> Signed-off-by: Xiaotian Feng <dannyfeng@...cent.com>
>> ---
>>  block/blk-ioc.c |    6 ++++++
>>  1 files changed, 6 insertions(+), 0 deletions(-)
>>
>> diff --git a/block/blk-ioc.c b/block/blk-ioc.c
>> index 8b782a6..9690f27 100644
>> --- a/block/blk-ioc.c
>> +++ b/block/blk-ioc.c
>> @@ -145,6 +145,7 @@ static void ioc_release_fn(struct work_struct *work)
>>  void put_io_context(struct io_context *ioc)
>>  {
>>  	unsigned long flags;
>> +	bool free_ioc = false;
>>  
>>  	if (ioc == NULL)
>>  		return;
>> @@ -159,8 +160,13 @@ void put_io_context(struct io_context *ioc)
>>  		spin_lock_irqsave(&ioc->lock, flags);
>>  		if (!hlist_empty(&ioc->icq_list))
>>  			schedule_work(&ioc->release_work);
>> +		else
>> +			free_ioc = true;
>>  		spin_unlock_irqrestore(&ioc->lock, flags);
>>  	}
>> +
>> +	if (free_ioc)
>> +		kmem_cache_free(iocontext_cachep, ioc);
>>  }
>>  EXPORT_SYMBOL(put_io_context);
> 
> This one looks good to me. Tejun?

It's definitely a leak. I have applied it.

-- 
Jens Axboe

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