6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Michal Luczaj mhal@rbox.co
[ 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 jakub@cloudflare.com Signed-off-by: Michal Luczaj mhal@rbox.co Reviewed-by: Willem de Bruijn willemb@google.com Link: https://patch.msgid.link/20250609-skisreadable-toctou-v1-1-d0dfb2d62c37@rbox... Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- include/net/sock.h | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/include/net/sock.h b/include/net/sock.h index e716b2ba00bba..e00cd9d0bec8e 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -3061,8 +3061,11 @@ int sock_copy_user_timeval(struct __kernel_sock_timeval *tv,
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 */