From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9C9AE19D8BC; Fri, 3 Apr 2026 15:52:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775231523; cv=none; b=Qvc1EoIgcbYN7drRiOYxC0dO0lvRlv0aKXcJMQVvweXJjLTnFCJxdxa1CqyJowxGEBCMHvIEeD6u76uYj4GnDAvhcSL2W7Mcuui17HjCU+ukgpTYxlivMN5cMNCFhYWxc28uE2QFVaaGLkRTOtSP4KKc3VIITZ7sMWBA0ksj6c8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775231523; c=relaxed/simple; bh=T00enF+tM+c3R9+3ciB5lD7rT69eMH/mHt84kQyP3QU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Ca882d6bBJj2tsu8NaHyzGiwK7zF0eRIuyF2XUGhoMUkudrUtAiyTFpHVKfNUJ6YIHNHGWNdtytS8UgPumTXH/uBaTS0WOl+4DHYBVy3cY0zevXa347PPOfO8RJQlBY2SfWpDQvkilmzdwNhF+AFZzjRDyfvgKAsJvgt/6W0bnY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=bV0zjIzf; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="bV0zjIzf" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 40515C4CEF7; Fri, 3 Apr 2026 15:52:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1775231523; bh=T00enF+tM+c3R9+3ciB5lD7rT69eMH/mHt84kQyP3QU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=bV0zjIzfe/iavTQdfE5UAE+Gsfr14/+sMuDBcihv/dvGBrPtIp2qSZ0kNpXdSxd2V ks5kicS7WSz3xTF+S9isD9P3XVisTWHdtneJaDoCNyn9go9NY8ivpmkQEUJoWL4Mcl D964E7JL9ewFBX4OJqC9Xbf7JdhHLGsfNcVf1EzDTMc4cbRXmVK+1IILSOHq/F9GTv O5q8/93m0OTJ0im2LrHW2PX36/PPH0MaJ0nNAiTeR212VLGbYoE0FyjqvvdLefQhD1 vLy4NVzES1/5BasAAKKkjll317u5cHCh9B41ZIO9uy64e+MDUiW4dG62Frs83ek00o LLYnYYcJZMfOA== Date: Fri, 3 Apr 2026 16:51:58 +0100 From: Simon Horman To: Oleh Konko Cc: "netdev@vger.kernel.org" , "jmaloy@redhat.com" , "davem@davemloft.net" , "edumazet@google.com" , "kuba@kernel.org" , "pabeni@redhat.com" , "tipc-discussion@lists.sourceforge.net" , "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" Subject: Re: [PATCH net v3] tipc: fix bc_ackers underflow on duplicate GRP_ACK_MSG Message-ID: <20260403155158.GL113102@horms.kernel.org> References: <41a4833f368641218e444fdcff822039.security@1seal.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <41a4833f368641218e444fdcff822039.security@1seal.org> On Thu, Apr 02, 2026 at 09:48:57AM +0000, Oleh Konko wrote: > The GRP_ACK_MSG handler in tipc_group_proto_rcv() currently decrements > bc_ackers on every inbound group ACK, even when the same member has > already acknowledged the current broadcast round. > > Because bc_ackers is a u16, a duplicate ACK received after the last > legitimate ACK wraps the counter to 65535. Once wrapped, > tipc_group_bc_cong() keeps reporting congestion and later group > broadcasts on the affected socket stay blocked until the group is > recreated. > > Fix this by ignoring duplicate or stale ACKs before touching bc_acked or > bc_ackers. This makes repeated GRP_ACK_MSG handling idempotent and > prevents the underflow path. > > Fixes: 2f487712b893 ("tipc: guarantee that group broadcast doesn't bypass group unicast") > Cc: stable@vger.kernel.org > Signed-off-by: Oleh Konko > --- > v3: > - correct the Fixes tag to the commit that introduced GRP_ACK_MSG and bc_ackers > > v2: > - make duplicate or stale GRP_ACK_MSG a full no-op via early return > - place acked in reverse xmas tree style Reviewed-by: Simon Horman