From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794590936; b=PklwFL8eqyMsnL+HvIlzNO1yfTrBgOjQ6ainqqemg7oIgWJm9Jd1BYUoBkftj3ogYKNo dlhuDK3Xun4Jq1Cns6CqfLfKrd8cIy9dhF4M6cz9kUj9RYS1Wm5IGJQGE7BRorCeMdv4y vYV12+toQIGyKzmDi0ln3kC8xoP7IAl94+SLkgR8LJe2ceJ5BgHJUAihu+NPWyGCfs1dd wCooWIKDeQCgedE8cfGFjacEbnezah88NIPK2Op8HB/B4fEORvRdB1o7sf7VPTEXPOeAa YWGFlO0sYDyiv/U5YnJhMVYKmt8jAIlTRtj9gFvKfqMcvfz2BXZe4xSaLK7t85ymsdw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794590936; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=7IGSn6q8MUFgpLkxAxcmglZbTlMGZJUe0tSOiuclUUA=; b=cEs+tFgSGoKyfn0ksqqpXw/aK0FpISqWw48Jq5r20KO67C8OS0PCVTF8GfxDKZWYBG1X N1xA0jFvlk+nNyw/uJcq2U1DspfVGOKx6LhLQq+gckiOHfS4XvX5I6xmrkwSpkt1BbBQR Wkci+P8GyB+pkM46FhuCPfOInXYL5kL4eHZ0//IquQFasH02K2v1A7cu+5YZqjXt+Zx4j 40bExusFj2XFRQGMl9LucObpwUydoMnkAUEhRi6RXsBq++iPzsmXCyOKL3+7Z341wE0TV gba6edAjMUIAdj/7dYrRTavxRAt15ckOv6Bo6YdX/8HVfFlaAMIV56hnfCQ8c7XoyEQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=1usYN3a6; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BD723606B441; Fri, 13 Nov 2026 17:28:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=1usYN3a6 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6A8A71F000C4; Fri, 13 Nov 2026 17:28:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794590936; bh=7IGSn6q8MUFgpLkxAxcmglZbTlMGZJUe0tSOiuclUUA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=1usYN3a6y7KrTyR0uQCS37CsU5GAmhzgvVSyst6XwirCbTwz9HEjNW3dB7pZTy5gp ujGUip+atB3gwPOXTv+47zGk5rBusSONEok1ntbKkwHKr0fpQRPxN1QgTb9ezUH3on eb1Q0hC+SxXlDYQJstmCyWZe9P4fqxUKeipe9DQE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Bernard Pidoux , Sasha Levin Subject: [PATCH 6.12 121/670] ax25: keep the window below 8 when a socket goes back to modulo 8 Date: Fri, 13 Nov 2026 10:44:45 -0500 Message-ID: <20261113153815.918545871@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261113153811.177190860@linuxfoundation.org> References: <20261113153811.177190860@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Bernard Pidoux AX25_WINDOW accepts 1 to 63 on a socket in extended mode, but AX25_EXTSEQ set back to 0 leaves the window as it was. With modulo 8, ax25_kick() computes the end of the window as (V(A) + window) % 8: a window of 8, 16, ... 56 gives V(A) itself, the window looks full, and the connection never sends an I frame. Other values wrap round to a smaller window. Bring the window down to 7 when AX25_EXTSEQ selects modulo 8. Tested on a QEMU bench (6.12.94 with KASAN and lockdep, two guests over a KISS serial link). B sets AX25_EXTSEQ 1, AX25_WINDOW 16, AX25_EXTSEQ 0, calls A with a SABM and sends 5 messages: before: window read back 16, A receives none of the 5 messages after: window read back 7, A receives the 5 messages Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Bernard Pidoux Assisted-by: Claude:claude-opus-5-5 (cherry picked from commit bcd2f2d49b5af392504f29292cbd622d857507b6) Signed-off-by: Sasha Levin --- net/ax25/af_ax25.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c index 08b196ddaba5e..43f4ea1ef88e8 100644 --- a/net/ax25/af_ax25.c +++ b/net/ax25/af_ax25.c @@ -708,6 +708,12 @@ static int ax25_setsockopt(struct socket *sock, int level, int optname, case AX25_EXTSEQ: ax25->modulus = opt ? AX25_EMODULUS : AX25_MODULUS; + /* + * A window set for modulo 128 may not fit modulo 8: + * ax25_kick() would then find it full and send nothing. + */ + if (ax25->modulus == AX25_MODULUS && ax25->window > 7) + ax25->window = 7; break; case AX25_PIDINCL: -- 2.53.0