[PATCH v2] powerpc/8xx: fix possible object reference leak

[Michael Ellerman]

Peng Hao <peng.hao2 at zte.com.cn> writes:

> From: Wen Yang <wen.yang99 at zte.com.cn>
>
> 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.
>
> 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.
>
> Fixes: a8db8cf0d894 ("irq_domain: Replace irq_alloc_host() with
> revmap-specific initializers")
> Signed-off-by: Wen Yang <wen.yang99 at zte.com.cn>
> Suggested-by: Christophe Leroy <christophe.leroy at c-s.fr>
> Reviewed-by: Peng Hao <peng.hao2 at zte.com.cn>
> Cc: Vitaly Bordug <vitb at kernel.crashing.org>
> Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
> Cc: Paul Mackerras <paulus at samba.org>
> Cc: Michael Ellerman <mpe at ellerman.id.au>
> Cc: linuxppc-dev at lists.ozlabs.org
> Cc: linux-kernel at vger.kernel.org
> ---
>  arch/powerpc/platforms/8xx/pic.c | 2 --
>  1 file changed, 2 deletions(-)
>
> diff --git a/arch/powerpc/platforms/8xx/pic.c b/arch/powerpc/platforms/8xx/pic.c
> index 8d5a25d..4453df6 100644
> --- 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;

It's fragile to rely on ret being equal to zero here. If the code
further up is changed it's easy enough to miss that ret is expected to
be zero.

Better to set it to zero here explicitly, this is the success path after
all, eg:

	ret = 0;

>  out:
>  	of_node_put(np);


cheers