Re: [PATCH net] ax25: use after free in ax25_connect
From: Eric Dumazet <hidden>
Date: 2022-01-11 20:57:06
Also in:
linux-hams, lkml
On 1/10/22 20:20, Hangyu Hua wrote:
sk_to_ax25(sk) needs to be called after lock_sock(sk) to avoid UAF caused by a race condition.
Can you describe what race condition you have found exactly ? sk pointer can not change.
quoted hunk ↗ jump to hunk
Signed-off-by: Hangyu Hua <redacted> --- net/ax25/af_ax25.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c index cfca99e295b8..c5d62420a2a8 100644 --- a/net/ax25/af_ax25.c +++ b/net/ax25/af_ax25.c@@ -1127,7 +1127,7 @@ static int __must_check ax25_connect(struct socket *sock, struct sockaddr *uaddr, int addr_len, int flags) { struct sock *sk = sock->sk; - ax25_cb *ax25 = sk_to_ax25(sk), *ax25t; + ax25_cb *ax25, *ax25t; struct full_sockaddr_ax25 *fsa = (struct full_sockaddr_ax25 *)uaddr; ax25_digi *digi = NULL; int ct = 0, err = 0;@@ -1155,6 +1155,8 @@ static int __must_check ax25_connect(struct socket *sock, lock_sock(sk); + ax25 = sk_to_ax25(sk); + /* deal with restarts */ if (sock->state == SS_CONNECTING) { switch (sk->sk_state) {