Re: [PATCH v3] kernel/signal.c: fix BUG_ON with SIG128 (MIPS)

[James Hogan]

On 25/06/13 23:13, James Hogan wrote:
> On 25 June 2013 22:40, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>> Meanwhile, unprivileged users can make a MIPS kernel go BUG.
>>
>> How much of a problem is this?  Obviously less of a problem with MIPS
>> than it would be with some other CPU types, but I'd imagine it's still
>> awkward in some environments.
>>
>> If this _is_ considered a problem, can we think of some nasty little
>> hack which at least makes the effects less damaging, which we can also
>> put into -stable kernels?
> 
> The first rfc patch I sent sort of satisfies that by passing 127 if
> sig==128, or slightly better would be passing 126 if sig>=127 (so that
> SIFSIGNALED returns true). Effectively #ifdef'ing it on _NSIG>127 as
> this patch does may be preferable too.
> 
> That's probably the minimum change necessary to evade the BUG_ON
> without removing it. The wait status code will still be wrong, but it
> wasn't exactly right before so it's no worse.
> 
> IMO changing the ABI by reducing _NSIG to 127 or 126 isn't appropriate
> for stable.

How does this look for a nasty/stable fix?