Commit 2660a544 authored by Michal Luczaj's avatar Michal Luczaj Committed by Jakub Kicinski
Browse files

net: Fix TOCTOU issue in sk_is_readable() 



sk->sk_prot->sock_is_readable is a valid function pointer when sk resides
in a sockmap. After the last sk_psock_put() (which usually happens when
socket is removed from sockmap), sk->sk_prot gets restored and
sk->sk_prot->sock_is_readable becomes NULL.

This makes sk_is_readable() racy, if the value of sk->sk_prot is reloaded
after the initial check. Which in turn may lead to a null pointer
dereference.

Ensure the function pointer does not turn NULL after the check.

Fixes: 8934ce2f ("bpf: sockmap redirect ingress support")
Suggested-by: default avatarJakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: default avatarMichal Luczaj <mhal@rbox.co>
Reviewed-by: default avatarWillem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20250609-skisreadable-toctou-v1-1-d0dfb2d62c37@rbox.co


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent dc9c6782

include/net/sock.h

+5 −2
Original line number Diff line number Diff line
@@ -3010,8 +3010,11 @@ int sock_ioctl_inout(struct sock *sk, unsigned int cmd, 
int sk_ioctl(struct sock *sk, unsigned int cmd, void __user *arg);

static inline bool sk_is_readable(struct sock *sk)

{

	if (sk->sk_prot->sock_is_readable)

		return sk->sk_prot->sock_is_readable(sk);

	const struct proto *prot = READ_ONCE(sk->sk_prot);



	if (prot->sock_is_readable)

		return prot->sock_is_readable(sk);



	return false;

}

#endif	/* _SOCK_H */