Re: [PATCH] powerpc: 8xx: fix a return value error in mpc8xx_pic_init

From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Michael Ellerman <mpe@ellerman.id.au>,
	Hangyu Hua <hbh25y@gmail.com>,
	"benh@kernel.crashing.org" <benh@kernel.crashing.org>,
	"paulus@samba.org" <paulus@samba.org>,
	"peng.hao2@zte.com.cn" <peng.hao2@zte.com.cn>,
	"wen.yang99@zte.com.cn" <wen.yang99@zte.com.cn>
Cc: "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] powerpc: 8xx: fix a return value error in mpc8xx_pic_init
Date: Wed, 9 Mar 2022 07:21:28 +0000	[thread overview]
Message-ID: <87b40493-7630-f714-27f4-90ad2a5a7c12@csgroup.eu> (raw)
In-Reply-To: <87o82fn6yw.fsf@mpe.ellerman.id.au>

Le 09/03/2022 à 04:24, Michael Ellerman a écrit :
> Hangyu Hua <hbh25y@gmail.com> writes:
>> mpc8xx_pic_init() should return -ENOMEM instead of 0 when
>> irq_domain_add_linear() return NULL. This cause mpc8xx_pics_init to continue
>> executing even if mpc8xx_pic_host is NULL.
>>
>> Fixes: cc76404feaed ("powerpc/8xx: Fix possible device node reference leak")
>> Signed-off-by: Hangyu Hua <hbh25y@gmail.com>
>> ---
>>   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 f2ba837249d6..04a6abf14c29 100644
>> --- a/arch/powerpc/platforms/8xx/pic.c
>> +++ b/arch/powerpc/platforms/8xx/pic.c
>> @@ -153,6 +153,7 @@ int __init mpc8xx_pic_init(void)
> 
> Expanding the context:
> 
> 	siu_reg = ioremap(res.start, resource_size(&res));
> 	if (siu_reg == NULL) {
> 		ret = -EINVAL;
> 		goto out;
> 	}
> 
> 	mpc8xx_pic_host = irq_domain_add_linear(np, 64, &mpc8xx_pic_host_ops, NULL);
>>   	if (mpc8xx_pic_host == NULL) {
>>   		printk(KERN_ERR "MPC8xx PIC: failed to allocate irq host!\n");
>>   		ret = -ENOMEM;
>> +		goto out;
>>   	}
>>   
>>   	ret = 0;
>>   	
> out:
> 	of_node_put(np);
> 	return ret;
> }
> 
> Proper error cleanup should also undo the ioremap() if
> irq_domain_add_linear() fails.

Uh ...

If siu_reg is NULL, you get a serious problem when __do_irq() calls 
mpc8xx_get_irq()

unsigned int mpc8xx_get_irq(void)
{
	int irq;

	/* For MPC8xx, read the SIVEC register and shift the bits down
	 * to get the irq number.
	 */
	irq = in_be32(&siu_reg->sc_sivec) >> 26;

	if (irq == PIC_VEC_SPURRIOUS)
		return 0;

         return irq_linear_revmap(mpc8xx_pic_host, irq);

}

So I'll leave siu_reg as is even if irq_domain_add_linear() fails.

Whatever, if we do something about that it should be done in another 
patch I think.

Christophe