Re: [PATCH v2] net: tipc: fix possible infoleak in tipc_mon_rcv()

[Hangyu Hua]

On 2022/6/30 11:31, Jakub Kicinski wrote:
> On Tue, 28 Jun 2022 16:31:22 +0800 Hangyu Hua wrote:
> > dom_bef is use to cache current domain record only if current domain
> > exists. But when current domain does not exist, dom_bef will still be used
> > in mon_identify_lost_members. This may lead to an information leak.
>
> AFAICT applied_bef must be zero if peer->domain was 0, so I don't think
> mon_identify_lost_members() will do anything.

void tipc_mon_rcv(struct net *net, void *data, u16 dlen, u32 addr,
		  struct tipc_mon_state *state, int bearer_id)
{
...
	if (!dom || (dom->len < new_dlen)) {
		kfree(dom);
		dom = kmalloc(new_dlen, GFP_ATOMIC);	<--- [1]
		peer->domain = dom;
		if (!dom)
			goto exit;
	}
...
}

peer->domain will be NULL when [1] fails. But there will not change 
peer->applied to 0. In this case, if tipc_mon_rcv is called again then 
an information leak will happen.

Thanks,
Hangyu.

> > Fix this by adding a memset before using dom_bef.
> >
> > Fixes: 35c55c9877f8 ("tipc: add neighbor monitoring framework")
> > Signed-off-by: Hangyu Hua <hbh25y@xxxxxxxxx>