Re: [PATCH v2] block: fix ioc leak in put_io_context

From: Jens Axboe
Date: Tue Mar 13 2012 - 10:41:08 EST


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@xxxxxxxxxxx>
>> ---
>> 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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