Re: [RFC v5][PATCH 2/8] General infrastructure for checkpoint restart

Oren Laadan
2008-09-15T18:53:04Z

Dave Hansen wrote:
> On Sat, 2008-09-13 at 19:06 -0400, Oren Laadan wrote:
>> +void *cr_hbuf_get(struct cr_ctx *ctx, int n)
>> +{
>> + void *ptr;
>> +
>> + BUG_ON(ctx->hpos + n > CR_HBUF_TOTAL);
>> + ptr = (void *) (((char *) ctx->hbuf) + ctx->hpos);
>> + ctx->hpos += n;
>> + return ptr;
>> +}
>
> All of the casting here is unnecessary. 'void *' behaves like 'char *'
> when you do arithmetic on it.

ok.

>
> I really do detest having a memory allocator BUG_ON() when it runs out
> of space.

The BUG_ON() statement asserts that we don't run out of buffer space.
Buffer usage is a function of the checkpoint/restart logic, and does
not depend on user input, hence not susceptible to DoS.

In other words, if the code is correct, this should never happen (much
like a kernel stack overflow), and if it happens it's a kernel bug. I
think it was Arnd who recommended with regard to this to crash loudly
if there is a bug in the kernel ...

Oren.