From: Eric Dumazet edumazet@google.com
[ Upstream commit 6a2febec338df7e7699a52d00b2e1207dcf65b28 ]
MD5 keys are read with RCU protection, and tcp_md5_do_add() might update in-place a prior key.
Normally, typical RCU updates would allocate a new piece of memory. In this case only key->key and key->keylen might be updated, and we do not care if an incoming packet could see the old key, the new one, or some intermediate value, since changing the key on a live flow is known to be problematic anyway.
We only want to make sure that in the case key->keylen is changed, cpus in tcp_md5_hash_key() wont try to use uninitialized data, or crash because key->keylen was read twice to feed sg_init_one() and ahash_request_set_crypt()
Fixes: 9ea88a153001 ("tcp: md5: check md5 signature without socket lock") Signed-off-by: Eric Dumazet edumazet@google.com Cc: Mathieu Desnoyers mathieu.desnoyers@efficios.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv4/tcp.c | 7 +++++-- net/ipv4/tcp_ipv4.c | 3 +++ 2 files changed, 8 insertions(+), 2 deletions(-)
--- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -3756,10 +3756,13 @@ 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; struct scatterlist sg;
- sg_init_one(&sg, key->key, key->keylen); - ahash_request_set_crypt(hp->md5_req, &sg, NULL, key->keylen); + 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); } EXPORT_SYMBOL(tcp_md5_hash_key); --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -1065,6 +1065,9 @@ int tcp_md5_do_add(struct sock *sk, cons if (key) { /* Pre-existing entry - just update that one. */ memcpy(key->key, newkey, newkeylen); + + smp_wmb(); /* pairs with smp_rmb() in tcp_md5_hash_key() */ + key->keylen = newkeylen; return 0; }