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([2a04:241e:502:a09c:cbe0:7b37:373:7410]) by smtp.gmail.com with ESMTPSA id kz3-20020a17090777c300b0073d68d2fc29sm28375ejc.218.2022.09.07.11.09.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 07 Sep 2022 11:09:10 -0700 (PDT) Message-ID: <9d26bcb4-b55f-29d5-9790-2a800b22a3a5@gmail.com> Date: Wed, 7 Sep 2022 21:09:08 +0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH v8 01/26] tcp: authopt: Initial support and key management Content-Language: en-US To: Eric Dumazet Cc: David Ahern , Dmitry Safonov <0x7f454c46@gmail.com>, Francesco Ruggeri , Salam Noureddine , Philip Paeps , Shuah Khan , "David S. Miller" , Herbert Xu , Kuniyuki Iwashima , Hideaki YOSHIFUJI , Jakub Kicinski , Yuchung Cheng , Mat Martineau , Christoph Paasch , Ivan Delalande , Caowangbao , Priyaranjan Jha , netdev , "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" , "open list:KERNEL SELFTEST FRAMEWORK" , LKML References: <0e4c0a98509b907e33c2f80b95cc6cfe713ac2b2.1662361354.git.cdleonard@gmail.com> <4a47b4ea-750c-a569-5754-4aa0cd5218fc@gmail.com> From: Leonard Crestez In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 9/7/22 19:28, Eric Dumazet wrote: > On Wed, Sep 7, 2022 at 9:19 AM Leonard Crestez wrote: >> >> On 9/7/22 01:57, Eric Dumazet wrote: >>> On Mon, Sep 5, 2022 at 12:06 AM Leonard Crestez wrote: >>>> >>>> This commit adds support to add and remove keys but does not use them >>>> further. >>>> >>>> Similar to tcp md5 a single pointer to a struct tcp_authopt_info* struct >>>> is added to struct tcp_sock, this avoids increasing memory usage. The >>>> data structures related to tcp_authopt are initialized on setsockopt and >>>> only freed on socket close. >>>> >>> >>> Thanks Leonard. >>> >>> Small points from my side, please find them attached. >> >> ... >> >>>> +/* Free info and keys. >>>> + * Don't touch tp->authopt_info, it might not even be assigned yes. >>>> + */ >>>> +void tcp_authopt_free(struct sock *sk, struct tcp_authopt_info *info) >>>> +{ >>>> + kfree_rcu(info, rcu); >>>> +} >>>> + >>>> +/* Free everything and clear tcp_sock.authopt_info to NULL */ >>>> +void tcp_authopt_clear(struct sock *sk) >>>> +{ >>>> + struct tcp_authopt_info *info; >>>> + >>>> + info = rcu_dereference_protected(tcp_sk(sk)->authopt_info, lockdep_sock_is_held(sk)); >>>> + if (info) { >>>> + tcp_authopt_free(sk, info); >>>> + tcp_sk(sk)->authopt_info = NULL; >>> >>> RCU rules at deletion mandate that the pointer must be cleared before >>> the call_rcu()/kfree_rcu() call. >>> >>> It is possible that current MD5 code has an issue here, let's not copy/paste it. >> >> OK. Is there a need for some special form of assignment or is current >> plain form enough? > > It is the right way (when clearing the pointer), no need for another form. OK >>>> +/* checks that ipv4 or ipv6 addr matches. */ >>>> +static bool ipvx_addr_match(struct sockaddr_storage *a1, >>>> + struct sockaddr_storage *a2) >>>> +{ >>>> + if (a1->ss_family != a2->ss_family) >>>> + return false; >>>> + if (a1->ss_family == AF_INET && >>>> + (((struct sockaddr_in *)a1)->sin_addr.s_addr != >>>> + ((struct sockaddr_in *)a2)->sin_addr.s_addr)) >>>> + return false; >>>> + if (a1->ss_family == AF_INET6 && >>>> + !ipv6_addr_equal(&((struct sockaddr_in6 *)a1)->sin6_addr, >>>> + &((struct sockaddr_in6 *)a2)->sin6_addr)) >>>> + return false; >>>> + return true; >>>> +} >>> >>> Always surprising to see this kind of generic helper being added in a patch. >> >> I remember looking for an equivalent and not finding it. Many places >> have distinct code paths for ipv4 and ipv6 and my use of >> "sockaddr_storage" as ipv4/ipv6 union is uncommon. > > inetpeer_addr_cmp() might do it (and we also could fix a bug in it it > seems, at least for __tcp_get_metrics() usage :/ That uses a different `struct inetpeer_addr` which also has some extra "vif" fields for ipv4 that I don't know about. Everybody seems to be rolling their own ipv4/v6 union, other examples are `struct tcp_md5_addr` and `xfrm_address_t`. struct sockaddr_storage is "more standard" but also larger so maybe that's why others don't use it. >>>> +int tcp_get_authopt_val(struct sock *sk, struct tcp_authopt *opt) >>>> +{ >>>> + struct tcp_sock *tp = tcp_sk(sk); >>>> + struct tcp_authopt_info *info; >>>> + >>>> + memset(opt, 0, sizeof(*opt)); >>>> + sock_owned_by_me(sk); >>>> + >>>> + info = rcu_dereference_check(tp->authopt_info, lockdep_sock_is_held(sk)); >>> >>> Probably not a big deal, but it seems the prior sock_owned_by_me() >>> might be redundant. >> >> The sock_owned_by_me call checks checks lockdep_sock_is_held >> >> The rcu_dereference_check call checks lockdep_sock_is_held || >> rcu_read_lock_held() > > Then if you own the socket lock, no need for rcu_dereference_check() > > It could be instead an rcu_dereference_protected(). This is stronger, because > if your thread no longer owns the socket lock, but is inside > rcu_read_lock(), we would > still get a proper lockdep splat. Ok, I think there are several places where rcu_dereference_check is incorrectly used instead of rcu_dereference_protected.