On 08/11/2017 01:15 PM, Dan Carpenter wrote:
> Hello Benjamin Herrenschmidt,
>
> This is a semi-automatic email about new static checker warnings.
>
> The patch 424de9c6e3f8: "powerpc/mm/radix: Avoid flushing the PWC on
> every flush_tlb_range" from Jul 19, 2017, leads to the following
> Smatch complaint:
>
> arch/powerpc/mm/tlb-radix.c:368 radix__flush_tlb_collapsed_pmd()
> error: we previously assumed 'mm' could be null (see line 362)
>
> arch/powerpc/mm/tlb-radix.c
> 361
> 362 pid = mm ? mm->context.id : 0;
> ^^
> Check for NULL.
>
> 363 if (unlikely(pid == MMU_NO_CONTEXT))
> 364 goto no_context;
> 365
> 366 /* 4k page size, just blow the world */
> 367 if (PAGE_SIZE == 0x1000) {
> 368 radix__flush_all_mm(mm);
> ^^
> Unchecked dereference.
Appears to be a false positive. MMU_NO_CONTEXT I believe is defined as "0". So,
maybe it
would be clearer that we take the goto branch if this line read:
362 pid = mm ? mm->context.id : MMU_NO_CONTEXT;
-Tyrel
>
> 369 return;
> 370 }
>
> regards,
> dan carpenter
>
