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

From: Oren Laadan
Date: Mon Sep 15 2008 - 14:53:04 EST

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.


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 ...

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