Re: [PATCH] net: tls: fix possible race condition between do_tls_getsockopt_conf() and do_tls_setsockopt_conf()

Sabrina Dubroca
2023-02-24T21:49:21Z

2023-02-24, 13:06:25 -0800, Jakub Kicinski wrote:
> On Fri, 24 Feb 2023 21:22:43 +0100 Sabrina Dubroca wrote:
> > > Right, the bug and the fix seem completely bogus.
> > > Please make sure the bugs are real and the fixes you sent actually
> > > fix them.
> >
> > I suggested a change of locking in do_tls_getsockopt_conf this
> > morning [1]. The issue reported last seemed valid, but this patch is not
> > at all what I had in mind.
> > [1] https://lore.kernel.org/all/Y/ht6gQL+u6fj3dG@hog/
>
> Ack, I read the messages out of order, sorry.
>
> > do_tls_setsockopt_conf fills crypto_info immediately from what
> > userspace gives us (and clears it on exit in case of failure), which
> > getsockopt could see since it's not locking the socket when it checks
> > TLS_CRYPTO_INFO_READY. So getsockopt would progress up to the point it
> > finally locks the socket, but if setsockopt failed, we could have
> > cleared TLS_CRYPTO_INFO_READY and freed iv/rec_seq.
>
> Makes sense. We should just take the socket lock around all of
> do_tls_getsockopt(), then?

That would make things simple and consistent. My idea was just taking
the existing lock_sock in do_tls_getsockopt_conf out of the switch and
put it just above TLS_CRYPTO_INFO_READY.

While we're at it, should we move the

ctx->prot_info.version != TLS_1_3_VERSION

check in do_tls_setsockopt_no_pad under lock_sock? I don't think that
can do anything wrong (we'd have to get past this check just before a
failing setsockopt clears crypto_info, and even then we're just
reading a bit from the context), it just looks a bit strange. Or just
lock the socket around all of do_tls_setsockopt_no_pad, like the other
options we have.

--
Sabrina