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Message-ID: <52faaa10-f3e4-bca9-4bff-6f1ea7d26593@gmail.com> Date: Mon, 27 Feb 2023 11:26:18 +0800 From: Hangyu Hua <hbh25y@...il.com> To: Jakub Kicinski <kuba@...nel.org>, Sabrina Dubroca <sd@...asysnail.net> Cc: Florian Westphal <fw@...len.de>, borisp@...dia.com, john.fastabend@...il.com, davem@...emloft.net, edumazet@...gle.com, pabeni@...hat.com, davejwatson@...com, aviadye@...lanox.com, ilyal@...lanox.com, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] net: tls: fix possible race condition between do_tls_getsockopt_conf() and do_tls_setsockopt_conf() On 25/2/2023 06:17, Jakub Kicinski wrote: > 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. I know what you mean. I just think lock crypto_info can fix this simply. The original situation is: thread1 thread2(do_tls_getsockopt_conf) lock_sock(sk) do_tls_setsockopt_conf(crypto_info->cipher_type set) crypto_info = xxx cctx = &ctx->tx if(!TLS_CRYPTO_INFO_READY(crypto_info)) tls_set_device_offload(kmalloc cctx->iv) tls_set_sw_offload(fail and cctx->iv may not set to NULL) do_tls_setsockopt_conf(set crypto_info->cipher_type to NULL) release_sock(sk) lock_sock(sk) memcpy(xxx, cctx->iv, xxx) release_sock(sk) If we lock crypto_info: thread1 thread2(do_tls_getsockopt_conf) lock_sock(sk) do_tls_setsockopt_conf(crypto_info->cipher_type set) tls_set_device_offload(kmalloc cctx->iv) tls_set_sw_offload(fail and cctx->iv may not set to NULL) do_tls_setsockopt_conf(set crypto_info->cipher_type to NULL) release_sock(sk) lock_sock(sk) crypto_info = xxx cctx = &ctx->tx release_sock(sk) if(!TLS_CRYPTO_INFO_READY(crypto_info)) lock_sock(sk) memcpy(xxx, cctx->iv, xxx) release_sock(sk) >> >> 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(). In order to reduce ambiguity, I think it may be a good idea only to lock do_tls_getsockopt_conf() like we did in do_tls_setsockopt() It will look like: static int do_tls_getsockopt(struct sock *sk, int optname, char __user *optval, int __user *optlen) { int rc = 0; switch (optname) { case TLS_TX: case TLS_RX: + lock_sock(sk); rc = do_tls_getsockopt_conf(sk, optval, optlen, optname == TLS_TX); + release_sock(sk); break; case TLS_TX_ZEROCOPY_RO: rc = do_tls_getsockopt_tx_zc(sk, optval, optlen); break; case TLS_RX_EXPECT_NO_PAD: rc = do_tls_getsockopt_no_pad(sk, optval, optlen); break; default: rc = -ENOPROTOOPT; break; } return rc; } Of cause, I will clean the lock in do_tls_getsockopt_conf(). What do you guys think?
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