Re: [PATCH] lib: cpu_rmap: reject zero-sized maps

[Jackie Liu]

2026年7月18日 12:56, "Andrew Morton" <akpm@xxxxxxxxxxxxxxxxxxxx mailto:akpm@xxxxxxxxxxxxxxxxxxxx?to=%22Andrew%20Morton%22%20%3Cakpm%40linux-foundation.org%3E > 写到:


> 
> On Sat, 18 Jul 2026 12:21:55 +0800 Jackie Liu <liu.yun@xxxxxxxxx> wrote:
> 
> > 
> > From: Jackie Liu <liuyun01@xxxxxxxxxx>
> >  
> >  alloc_cpu_rmap() assigns an object index to each possible CPU using
> >  cpu % size. Passing zero therefore triggers a divide error instead of
> >  reporting that the map cannot be allocated.
> > 
> Is there any situation in which this is known to trigger?
> 
> > 
> > Reject zero along with sizes that do not fit in the u16 map indices.
> > 
> If passing zero is a caller bug then a divide-by-zero exception is a
> fine way of reporting it. So I'm not seeing a need to make any change
> here.
>

Thanks. I rechecked all in-tree callers and couldn't find a path which
can legitimately pass zero.  The size is either explicitly checked or
derived from successfully allocated IRQ/RX queue counts, whose minimum
is one.

So zero would indeed indicate a caller bug.  Please disregard this
patch.