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

[Christophe Leroy <christophe.leroy@csgroup.eu>]

Le 09/03/2022 à 11:46, Michael Ellerman a écrit :
> Christophe Leroy <christophe.leroy@csgroup.eu> writes:
>> 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()
> 
> Arguably it shouldn't be assigned to ppc_md.get_irq unless
> mpc8xx_pic_init() succeeds. See eg. xics_init().


I agree with that, but it's a huge work I guess. Most platforms set 
.get_irq in ppc_md() at buildtime. See the generic mpic_get_irq() which 
has a BUG_ON() in call mpic_primary is NULL. There are 50 platforms with 
buildtime assignment.

That would however be a good opportunity to switch get_irq() to a static 
call. I'll open a github issue to follow it.

Christophe