On Sun, Feb 22, 2026 at 4:35 AM Simon Baatz via B4 Relay <[email protected]> wrote: > > From: Simon Baatz <[email protected]> > > Commit 2bd99aef1b19 ("tcp: accept bare FIN packets under memory > pressure") allowed accepting FIN packets in tcp_data_queue() even when > the receive window was closed, to prevent ACK/FIN loops with broken > clients. > > Such a FIN packet is in sequence, but because the FIN consumes a > sequence number, it extends beyond the window. Before commit > 9ca48d616ed7 ("tcp: do not accept packets beyond window"), > tcp_sequence() only required the seq to be within the window. After > that change, the entire packet (including the FIN) must fit within the > window. As a result, such FIN packets are now dropped and the handling > path is no longer reached. > > Be more lenient by not counting the sequence number consumed by the > FIN when calling tcp_sequence(), restoring the previous behavior for > cases where only the FIN extends beyond the window. > > Fixes: 9ca48d616ed7 ("tcp: do not accept packets beyond window") > Signed-off-by: Simon Baatz <[email protected]>
Good catch, thanks ! Reviewed-by: Kuniyuki Iwashima <[email protected]>
