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

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Date:	Tue, 13 Mar 2012 10:28:20 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Xiaotian Feng <xtfeng@...il.com>
Cc:	axboe@...nel.dk, 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 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?

Acked-by: Vivek Goyal <vgoyal@...hat.com>

Vivek
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