On Fri, 24 Feb 2023 22:48:57 +0100 Sabrina Dubroca wrote:

2023-02-24, 13:06:25 -0800, Jakub Kicinski wrote:

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On Fri, 24 Feb 2023 21:22:43 +0100 Sabrina Dubroca wrote:  

 [...]  

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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.
  

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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().