Date:   Fri, 24 Feb 2023 21:22:43 +0100
From:   Sabrina Dubroca <sd@queasysnail.net>
To:     Jakub Kicinski <kuba@kernel.org>
Cc:     Hangyu Hua <hbh25y@gmail.com>, Florian Westphal <fw@strlen.de>,
        borisp@nvidia.com, john.fastabend@gmail.com, davem@davemloft.net,
        edumazet@google.com, pabeni@redhat.com, davejwatson@fb.com,
        aviadye@mellanox.com, ilyal@mellanox.com, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] net: tls: fix possible race condition between
 do_tls_getsockopt_conf() and do_tls_setsockopt_conf()
Message-ID: <Y/kck0/+NB+Akpoy@hog>
References: <20230224105811.27467-1-hbh25y@gmail.com>
 <20230224120606.GI26596@breakpoint.cc>
 <20230224105508.4892901f@kernel.org>
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2023-02-24, 10:55:08 -0800, Jakub Kicinski wrote:
> On Fri, 24 Feb 2023 13:06:06 +0100 Florian Westphal wrote:
> > Hangyu Hua <hbh25y@gmail.com> wrote:
> > > ctx->crypto_send.info is not protected by lock_sock in
> > > do_tls_getsockopt_conf(). A race condition between do_tls_getsockopt_conf()
> > > and do_tls_setsockopt_conf() can cause a NULL point dereference or
> > > use-after-free read when memcpy.  
> > 
> > Its good practice to quote the relevant parts of the splat here.
> 
> 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/

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.

-- 
Sabrina