Re: p used before making sure it is not NULL in kernel/auditsc.c

[Al Viro <viro@ZenIV.linux.org.uk>]

On Fri, May 22, 2009 at 10:22:41AM +0800, Zhenwen Xu wrote:
> p used before making sure it is not NULL in kernel/auditsc.c
> 
> here we should make sure the p is not NULL then use it.

NAK.  ->tree_count can become non-zero only after we had set ->trees
non-NULL.  It's "how much free slots is left in current->trees".
If it's zero, we might have an empty chain (->trees is NULL, we bugger
off and caller tries to allocate) *or* we might be at the end of the
chain (->trees->next is NULL, same as previous) *or* we have more
allocated blocks in the chain, so we move to the next block and
store in there.

As a general note,

	if (foo) {
		...
		dereference p;
		...
	} else if (p) {
		...
		dereference p;
		...
	}

is a perfectly sane code, if foo is true only when p != NULL.