diff options
| author | Kuniyuki Iwashima <kuniyu@amazon.co.jp> | 2021-01-18 08:59:20 +0300 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2021-01-20 19:56:16 +0300 |
| commit | c89dffc70b340780e5b933832d8c3e045ef3791e (patch) | |
| tree | a2be5f1b8798e1c177172a7d4e6e5f7531c43843 /net | |
| parent | b3741b43880bfb7319424edd600da47d1cd8c680 (diff) | |
| download | linux-c89dffc70b340780e5b933832d8c3e045ef3791e.tar.xz | |
tcp: Fix potential use-after-free due to double kfree()
Receiving ACK with a valid SYN cookie, cookie_v4_check() allocates struct
request_sock and then can allocate inet_rsk(req)->ireq_opt. After that,
tcp_v4_syn_recv_sock() allocates struct sock and copies ireq_opt to
inet_sk(sk)->inet_opt. Normally, tcp_v4_syn_recv_sock() inserts the full
socket into ehash and sets NULL to ireq_opt. Otherwise,
tcp_v4_syn_recv_sock() has to reset inet_opt by NULL and free the full
socket.
The commit 01770a1661657 ("tcp: fix race condition when creating child
sockets from syncookies") added a new path, in which more than one cores
create full sockets for the same SYN cookie. Currently, the core which
loses the race frees the full socket without resetting inet_opt, resulting
in that both sock_put() and reqsk_put() call kfree() for the same memory:
sock_put
sk_free
__sk_free
sk_destruct
__sk_destruct
sk->sk_destruct/inet_sock_destruct
kfree(rcu_dereference_protected(inet->inet_opt, 1));
reqsk_put
reqsk_free
__reqsk_free
req->rsk_ops->destructor/tcp_v4_reqsk_destructor
kfree(rcu_dereference_protected(inet_rsk(req)->ireq_opt, 1));
Calling kmalloc() between the double kfree() can lead to use-after-free, so
this patch fixes it by setting NULL to inet_opt before sock_put().
As a side note, this kind of issue does not happen for IPv6. This is
because tcp_v6_syn_recv_sock() clones both ipv6_opt and pktopts which
correspond to ireq_opt in IPv4.
Fixes: 01770a166165 ("tcp: fix race condition when creating child sockets from syncookies")
CC: Ricardo Dias <rdias@singlestore.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
Reviewed-by: Benjamin Herrenschmidt <benh@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20210118055920.82516-1-kuniyu@amazon.co.jp
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net')
| -rw-r--r-- | net/ipv4/tcp_ipv4.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 4e82745d336f..777306b5bc22 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -1595,6 +1595,8 @@ struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb, tcp_move_syn(newtp, req); ireq->ireq_opt = NULL; } else { + newinet->inet_opt = NULL; + if (!req_unhash && found_dup_sk) { /* This code path should only be executed in the * syncookie case only @@ -1602,8 +1604,6 @@ struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb, bh_unlock_sock(newsk); sock_put(newsk); newsk = NULL; - } else { - newinet->inet_opt = NULL; } } return newsk; |