Messages in this thread | | | Date | Fri, 24 Feb 2023 14:17:40 -0800 | From | Jakub Kicinski <> | Subject | Re: [PATCH] net: tls: fix possible race condition between do_tls_getsockopt_conf() and do_tls_setsockopt_conf() |
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On Fri, 24 Feb 2023 22:48:57 +0100 Sabrina Dubroca wrote: > 2023-02-24, 13:06:25 -0800, Jakub Kicinski wrote: > > On Fri, 24 Feb 2023 21:22:43 +0100 Sabrina Dubroca wrote: > [...] > > > > > > 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?
Yes, or READ_ONCE(), same for do_tls_getsockopt_tx_zc() and its access on ctx->zerocopy_sendfile.
> 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.
The delayed locking feels like a premature optimization, we'll keep having such issues with new options. Hence my vote to lock all of do_tls_getsockopt().
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