linux-kernel - Re: [PATCH] target: fix memory leak on XCOPY

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Date:	Sat, 17 May 2014 15:52:03 -0700
From:	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>
To:	Mikulas Patocka <mpatocka@...hat.com>
Cc:	linux-scsi@...r.kernel.org, target-devel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] target: fix memory leak on XCOPY

On Sat, 2014-05-17 at 06:49 -0400, Mikulas Patocka wrote:
> On each processed XCOPY command, two "kmalloc-512" memory objects are
> leaked. These represent two allocations of struct xcopy_pt_cmd in
> target_core_xcopy.c.
> 
> The reason for the memory leak is that the cmd_kref field is not
> initialized (thus, it is zero because the allocations were done with
> kzalloc). When we decrement zero kref in target_put_sess_cmd, the result
> is not zero, thus target_release_cmd_kref is not called.
> 
> This patch fixes the bug by moving kref initialization from
> target_get_sess_cmd to transport_init_se_cmd (this function is called from
> target_core_xcopy.c, so it will correctly initialize cmd_kref). It can be
> easily verified that all code that calls target_get_sess_cmd also calls
> transport_init_se_cmd earlier, thus moving kref_init shouldn't introduce
> any new problems.
> 
> Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>
> Cc: stable@...r.kernel.org	# 3.12+
> 
> ---
>  drivers/target/target_core_transport.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Index: linux-3.15-rc5/drivers/target/target_core_transport.c
> ===================================================================
> --- linux-3.15-rc5.orig/drivers/target/target_core_transport.c	2014-04-14 16:08:15.000000000 +0200
> +++ linux-3.15-rc5/drivers/target/target_core_transport.c	2014-05-16 18:24:57.000000000 +0200
> @@ -1113,6 +1113,7 @@ void transport_init_se_cmd(
>  	init_completion(&cmd->cmd_wait_comp);
>  	init_completion(&cmd->task_stop_comp);
>  	spin_lock_init(&cmd->t_state_lock);
> +	kref_init(&cmd->cmd_kref);
>  	cmd->transport_state = CMD_T_DEV_ACTIVE;
>  
>  	cmd->se_tfo = tfo;
> @@ -2357,7 +2358,6 @@ int target_get_sess_cmd(struct se_sessio
>  	unsigned long flags;
>  	int ret = 0;
>  
> -	kref_init(&se_cmd->cmd_kref);
>  	/*
>  	 * Add a second kref if the fabric caller is expecting to handle
>  	 * fabric acknowledgement that requires two target_put_sess_cmd()
> --

Applied.  Thanks alot Mikulas!

--nab

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