From: Eric Dumazet <edumazet@google.com>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>,
"David S. Miller" <davem@davemloft.net>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
netdev <netdev@vger.kernel.org>,
Yuchung Cheng <ycheng@google.com>,
Jonathan Rajotte-Julien <joraj@efficios.com>
Subject: Re: [regression] TCP_MD5SIG on established sockets
Date: Wed, 1 Jul 2020 08:15:10 -0700 [thread overview]
Message-ID: <CANn89iLLuUG-6QaOzTt8UFszpOKkjKhXqDmgDMW1L5GctsqL-g@mail.gmail.com> (raw)
In-Reply-To: <338284155.18826.1593605982156.JavaMail.zimbra@efficios.com>
On Wed, Jul 1, 2020 at 5:19 AM Mathieu Desnoyers
<mathieu.desnoyers@efficios.com> wrote:
> The approach below looks good to me, but you'll also need to annotate
> both tcp_md5_hash_key and tcp_md5_do_add with __no_kcsan or use
> data_race(expr) to let the concurrency sanitizer know that there is
> a known data race which is there on purpose (triggered by memcpy in tcp_md5_do_add
> and somewhere within crypto_ahash_update). See Documentation/dev-tools/kcsan.rst
> for details.
Sure, I can add a data_race() and let stable teams handle the
backports without it ;)
>
> Thanks,
>
> Mathieu
>
> >
> > diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> > index
> > f111660453241692a17c881dd6dc2910a1236263..c3af8180c7049d5c4987bf5c67e4aff2ed6967c9
> > 100644
> > --- a/net/ipv4/tcp.c
> > +++ b/net/ipv4/tcp.c
> > @@ -4033,11 +4033,9 @@ EXPORT_SYMBOL(tcp_md5_hash_skb_data);
> >
> > int tcp_md5_hash_key(struct tcp_md5sig_pool *hp, const struct
> > tcp_md5sig_key *key)
> > {
> > - u8 keylen = key->keylen;
> > + u8 keylen = READ_ONCE(key->keylen); /* paired with
> > WRITE_ONCE() in tcp_md5_do_add */
> > struct scatterlist sg;
> >
> > - smp_rmb(); /* paired with smp_wmb() in tcp_md5_do_add() */
> > -
> > sg_init_one(&sg, key->key, keylen);
> > ahash_request_set_crypt(hp->md5_req, &sg, NULL, keylen);
> > return crypto_ahash_update(hp->md5_req);
> > diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> > index
> > 99916fcc15ca0be12c2c133ff40516f79e6fdf7f..0d08e0134335a21d23702e6a5c24a0f2b3c61c6f
> > 100644
> > --- a/net/ipv4/tcp_ipv4.c
> > +++ b/net/ipv4/tcp_ipv4.c
> > @@ -1114,9 +1114,13 @@ int tcp_md5_do_add(struct sock *sk, const union
> > tcp_md5_addr *addr,
> > /* Pre-existing entry - just update that one. */
> > memcpy(key->key, newkey, newkeylen);
> >
> > - smp_wmb(); /* pairs with smp_rmb() in tcp_md5_hash_key() */
> > + /* Pairs with READ_ONCE() in tcp_md5_hash_key().
> > + * Also note that a reader could catch new key->keylen value
> > + * but old key->key[], this is the reason we use __GFP_ZERO
> > + * at sock_kmalloc() time below these lines.
> > + */
> > + WRITE_ONCE(key->keylen, newkeylen);
> >
> > - key->keylen = newkeylen;
> > return 0;
> > }
> >
> > @@ -1132,7 +1136,7 @@ int tcp_md5_do_add(struct sock *sk, const union
> > tcp_md5_addr *addr,
> > rcu_assign_pointer(tp->md5sig_info, md5sig);
> > }
> >
> > - key = sock_kmalloc(sk, sizeof(*key), gfp);
> > + key = sock_kmalloc(sk, sizeof(*key), gfp | __GFP_ZERO);
> > if (!key)
> > return -ENOMEM;
> > if (!tcp_alloc_md5sig_pool()) {
>
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com
next prev parent reply other threads:[~2020-07-01 15:15 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-13 19:38 [regression] TC_MD5SIG on established sockets Mathieu Desnoyers
2020-05-13 19:49 ` Eric Dumazet
2020-05-13 19:56 ` Eric Dumazet
2020-06-29 19:43 ` [regression] TCP_MD5SIG " Mathieu Desnoyers
2020-06-29 20:47 ` Eric Dumazet
2020-06-30 19:43 ` Linus Torvalds
2020-06-30 19:52 ` Linus Torvalds
2020-06-30 20:34 ` Mathieu Desnoyers
2020-06-30 20:39 ` Eric Dumazet
2020-06-30 20:44 ` David Miller
2020-06-30 20:56 ` Eric Dumazet
2020-06-30 21:17 ` Mathieu Desnoyers
2020-06-30 21:23 ` Eric Dumazet
2020-06-30 21:54 ` Eric Dumazet
2020-06-30 22:07 ` Eric Dumazet
2020-06-30 22:38 ` Eric Dumazet
2020-06-30 23:44 ` Mathieu Desnoyers
2020-07-01 0:01 ` Eric Dumazet
2020-07-01 2:02 ` Herbert Xu
2020-07-01 2:17 ` Eric Dumazet
2020-07-01 2:22 ` Herbert Xu
2020-07-01 2:30 ` Eric Dumazet
2020-07-01 2:39 ` Joe Perches
2020-07-01 2:58 ` Herbert Xu
2020-07-01 3:36 ` Eric Dumazet
2020-07-01 3:50 ` Herbert Xu
2020-07-01 12:19 ` Mathieu Desnoyers
2020-07-01 15:15 ` Eric Dumazet [this message]
2020-07-01 17:24 ` Eric Dumazet
2020-06-30 20:21 ` David Miller
2020-06-30 20:30 ` Eric Dumazet
2020-06-30 20:39 ` Mathieu Desnoyers
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