Re: [PATCH net v2 0/8] net: fixes for requests completing on a socket that no longer listens

On Mon, 24 Aug 2026 12:32:44 +0900
Hyunwoo Kim <[email protected]> wrote:

> connect(AF_UNSPEC) and listen() move a socket back and forth between
> listener and active session. IPV6_ADDRFORM on top of that turns an
> AF_INET6 socket into an AF_INET one.

Is it even valid to call connect() after listen()?

David

> 
> Two things follow. One is that what the socket had before the change is
> left behind: requests still in the ehash, and parent fields a child
> inherits. The other is that the socket is used while it is changing.
> tcp_check_req() does not hold the listener lock, and tcp_v{4,6}_rcv()
> reads sk_state twice without it on the listener path.
> 
> Patch 2 is neither. After a reuseport migration the listener that counted
> a request and the listener the count is decremented on are not the same.
> It goes with patch 3 because patch 3 needs it. Nothing ever resets that
> count, so patch 3 on its own has a check that can be bypassed.
> 
> Patches 2, 6, 7 and 8 are new in v2.
> 
> Hyunwoo Kim (8):
>   tcp: fix use-after-free of the listener's ipv6_pinfo after
>     IPV6_ADDRFORM
>   tcp: fix imbalanced icsk_accept_queue count in tcp_check_req()
>   ipv6: fix request socket use-after-free after IPV6_ADDRFORM
>   net: fix out-of-bounds write in sk_clone() racing with IPV6_ADDRFORM
>   tcp: do not inherit out_of_order_queue from parent
>   tcp: fix use-after-free in the lockless listener path
>   net: clear sk_tsq_flags in sk_clone()
>   tcp: do not inherit retransmit state from parent
> 
>  include/net/tcp.h        |  2 ++
>  net/core/sock.c          |  3 +-
>  net/ipv4/tcp_input.c     | 64 +++++++++++++++++++++++-----------------
>  net/ipv4/tcp_ipv4.c      | 52 ++++++++++++++++++++++++++++++--
>  net/ipv4/tcp_minisocks.c |  9 +++++-
>  net/ipv6/af_inet6.c      |  4 +++
>  net/ipv6/ipv6_sockglue.c | 15 ++++++++++
>  net/ipv6/tcp_ipv6.c      | 44 +++++++++++++++++++++++++--
>  8 files changed, 160 insertions(+), 33 deletions(-)
>