From: Michal Luczaj Date: Mon, 9 Jun 2025 17:08:03 +0000 (+0200) Subject: net: Fix TOCTOU issue in sk_is_readable() X-Git-Tag: v5.10.239~226 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=c2b26638476baee154920bb587fc94ff1bf04336;p=thirdparty%2Fkernel%2Fstable.git net: Fix TOCTOU issue in sk_is_readable() [ Upstream commit 2660a544fdc0940bba15f70508a46cf9a6491230 ] 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: 8934ce2fd081 ("bpf: sockmap redirect ingress support") Suggested-by: Jakub Sitnicki Signed-off-by: Michal Luczaj Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20250609-skisreadable-toctou-v1-1-d0dfb2d62c37@rbox.co Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- diff --git a/include/net/sock.h b/include/net/sock.h index b9e34b955c561..bc9a1e535d580 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -2827,8 +2827,11 @@ int sock_bind_add(struct sock *sk, struct sockaddr *addr, int addr_len); 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 */