linux-kernel - Re: [PATCH 5/5] powerpc/8xx: fix possible object reference leak

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Date:   Fri, 22 Mar 2019 07:09:37 +0000
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Wen Yang <wen.yang99@....com.cn>, linux-kernel@...r.kernel.org
Cc:     wang.yi59@....com.cn, Paul Mackerras <paulus@...ba.org>,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 5/5] powerpc/8xx: fix possible object reference leak



On 03/22/2019 03:05 AM, Wen Yang wrote:
> The call to of_find_compatible_node returns a node pointer with refcount
> incremented thus it must be explicitly decremented after the last
> usage.
> irq_domain_add_linear also calls of_node_get to increase refcount,
> so irq_domain will not be affected when it is released.


Should you have a:

Fixes: a8db8cf0d894 ("irq_domain: Replace irq_alloc_host() with 
revmap-specific initializers")

If not, it means your change is in contradiction with commit 
b1725c9319aa ("[POWERPC] arch/powerpc/sysdev: Add missing of_node_put")

> 
> Detected by coccinelle with the following warnings:
> ./arch/powerpc/platforms/8xx/pic.c:158:1-7: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 136, but without a corresponding object release within this function.
> 
> Signed-off-by: Wen Yang <wen.yang99@....com.cn>
> Cc: Vitaly Bordug <vitb@...nel.crashing.org>
> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: linuxppc-dev@...ts.ozlabs.org
> Cc: linux-kernel@...r.kernel.org
> ---
>   arch/powerpc/platforms/8xx/pic.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/arch/powerpc/platforms/8xx/pic.c b/arch/powerpc/platforms/8xx/pic.c
> index 8d5a25d..13d880b 100644
> --- a/arch/powerpc/platforms/8xx/pic.c
> +++ b/arch/powerpc/platforms/8xx/pic.c
> @@ -155,6 +155,7 @@ int mpc8xx_pic_init(void)
>   		ret = -ENOMEM;
>   		goto out;
>   	}
> +	of_node_put(np);
>   	return 0;
>   
>   out:
> 

I guess it would be better as follows:

--- a/arch/powerpc/platforms/8xx/pic.c
+++ b/arch/powerpc/platforms/8xx/pic.c
@@ -153,9 +153,7 @@ int mpc8xx_pic_init(void)
         if (mpc8xx_pic_host == NULL) {
                 printk(KERN_ERR "MPC8xx PIC: failed to allocate irq 
host!\n");
                 ret = -ENOMEM;
-               goto out;
         }
-       return 0;

  out:
         of_node_put(np);



Christophe