Re: [PATCH v2] unix: properly account for FDs passed over unix sockets

[Linus Torvalds]

On Tue, Feb 2, 2016 at 12:32 PM, Hannes Frederic Sowa
<hannes@xxxxxxxxxxxxxxxxxxx> wrote:
>
> Unfortunately we never transfer a scm_cookie via the skbs but merely use it
> to initialize unix_skb_parms structure in skb->cb and destroy it afterwards.

Ok, I obviously didn't check very closely.

> But "struct pid *" in unix_skb_parms should be enough to get us to
> corresponding "struct cred *" so we can decrement the correct counter during
> skb destruction.

Umm. I think the "struct cred" may change in between, can't it?

So I don't think you can later look up the cred based on the pid.

Could we add the cred pointer (or just the user pointer) to the unix_skb_parms?

Or maybe just add it to the "struct scm_fp_list"?

               Linus