RE: KASAN+netlink, was: [PATCH] [net-next?] hns: avoid stack overflow with CONFIG_KASAN

[David Laight <David.Laight@ACULAB.COM>]

> From: Johannes Berg
> Sent: 08 February 2017 12:24
...
> Btw, what's causing this to start with? Can't the compiler reuse the
> stack places?

Only if it realises they've gone out of scope - which probably
doesn't happen when the functions are inlined.
The address of the parameter can be saved by the calling function
and used in a later call.

Something like this is valid:

int foo(int *p, int v)
{
	static int *sv;
	int old = -1;
	if (sv) {old = *sv; *sv = v;}
	sv = v;
	return old;
}

void bar(...) {
	int a, b;
	...
	foo(&a, 0);
	...
	foo(&b, 1);
	...
	foo(NULL, 2);
	...

If the compiler starts sharing stack it all goes wrong.

	David