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authorEric Dumazet <edumazet@google.com>2020-06-30 16:41:01 -0700
committerDavid S. Miller <davem@davemloft.net>2020-06-30 18:14:38 -0700
commit6a2febec338df7e7699a52d00b2e1207dcf65b28 (patch)
tree778dc294a8c0a7f9ea767ac01539b3c2e58ba490 /net
parent28541f3d324f6de1e545e2875283b6cef95c5d36 (diff)
tcp: md5: add missing memory barriers in tcp_md5_do_add()/tcp_md5_hash_key()
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>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/tcp.c7
-rw-r--r--net/ipv4/tcp_ipv4.c3
2 files changed, 8 insertions, 2 deletions
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 810cc164f795..f11166045324 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4033,10 +4033,13 @@ 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);
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index ad6435ba6d72..99916fcc15ca 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1113,6 +1113,9 @@ int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
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;
}