From: Eric Dumazet <edumazet@xxxxxxxxxx>
[ 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@xxxxxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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
@@ -3880,10 +3880,13 @@ 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
@@ -1105,6 +1105,9 @@ 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;
}
