| Message ID | 21dd84bd44a8d0839564bed351e7d77a16b68474.1696237983.git.pabeni@redhat.com (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Commit | 4b8e173a713a1b707a012257356acfc7a66430f9 |
| Delegated to: | Matthieu Baerts |
| Headers | show |
| Series | [mptcp-next,v2,1/2] tcp: define initial scaling factor value as a macro | expand |
Hi Paolo, On 02/10/2023 11:13, Paolo Abeni wrote: > Christoph reported a couple of serious splat caused by > the mentioned patch. > > mptcp_set_rcvlowat() can use msk->scaling_ratio, before > such field is initialized, causing a divide by zero: we > need to init it in the sock constructor. > > Additionally the same function bogusly cast an msk to a > tcp_sock, causing memory corruption. The reproducer likely > clears the sk refcount for the next msk allocated into the > same slab. > > The intent was to properly propagate the rcvbuf changes to > the subflows. Let's do that explicitly. > > Signed-off-by: Paolo Abeni <pabeni@redhat.com> > -- > Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/442 > Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/443 Thank you for the patches! Now in our tree (I added patch 1/2 just before "mptcp: give rcvlowat some love") New patches for t/upstream: - 3a6e7c602676: tcp: define initial scaling factor value as a macro - 4b8e173a713a: "squashed" patch 2/2 in "mptcp: give rcvlowat some love" - Results: 3cbb19268039..ad8e597b726a (export) Tests are now in progress: https://cirrus-ci.com/github/multipath-tcp/mptcp_net-next/export/20231003T165758 Cheers, Matt
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 6f9e116598ed..990fcf53074a 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -2758,6 +2758,7 @@ static void __mptcp_init_sock(struct sock *sk) msk->rmem_fwd_alloc = 0; WRITE_ONCE(msk->rmem_released, 0); msk->timer_ival = TCP_RTO_MIN; + msk->scaling_ratio = TCP_DEFAULT_SCALING_RATIO; WRITE_ONCE(msk->first, NULL); inet_csk(sk)->icsk_sync_mss = mptcp_sync_mss; diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c index 340e87195a27..6b37946b5c52 100644 --- a/net/mptcp/sockopt.c +++ b/net/mptcp/sockopt.c @@ -1473,6 +1473,7 @@ void mptcp_sockopt_sync_locked(struct mptcp_sock *msk, struct sock *ssk) */ int mptcp_set_rcvlowat(struct sock *sk, int val) { + struct mptcp_subflow_context *subflow; int space, cap; if (sk->sk_userlocks & SOCK_RCVBUF_LOCK) @@ -1490,9 +1491,19 @@ int mptcp_set_rcvlowat(struct sock *sk, int val) return 0; space = __tcp_space_from_win(mptcp_sk(sk)->scaling_ratio, val); - if (space > sk->sk_rcvbuf) { - WRITE_ONCE(sk->sk_rcvbuf, space); - tcp_sk(sk)->window_clamp = val; + if (space <= sk->sk_rcvbuf) + return 0; + + /* propagate the rcvbuf changes to all the subflows */ + WRITE_ONCE(sk->sk_rcvbuf, space); + mptcp_for_each_subflow(mptcp_sk(sk), subflow) { + struct sock *ssk = mptcp_subflow_tcp_sock(subflow); + bool slow; + + slow = lock_sock_fast(ssk); + WRITE_ONCE(ssk->sk_rcvbuf, space); + tcp_sk(ssk)->window_clamp = val; + unlock_sock_fast(ssk, slow); } return 0; }
Christoph reported a couple of serious splat caused by the mentioned patch. mptcp_set_rcvlowat() can use msk->scaling_ratio, before such field is initialized, causing a divide by zero: we need to init it in the sock constructor. Additionally the same function bogusly cast an msk to a tcp_sock, causing memory corruption. The reproducer likely clears the sk refcount for the next msk allocated into the same slab. The intent was to properly propagate the rcvbuf changes to the subflows. Let's do that explicitly. Signed-off-by: Paolo Abeni <pabeni@redhat.com> -- Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/442 Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/443 since the above issues are introduced by the squash-to patch, I think we can't have the tag in the final patch. v1 -> v2: - use scaling_ratio define (Mat) --- net/mptcp/protocol.c | 1 + net/mptcp/sockopt.c | 17 ++++++++++++++--- 2 files changed, 15 insertions(+), 3 deletions(-)