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 21A4B28373 for ; Mon, 28 Jul 2025 14:09:08 +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=1753711749; cv=none; b=i9iUCljWDcmN5sUNuhu6uV2iaGvo6DpIwkCbOqn53+iYSgf1lVfi95zOkXVv1R8dMKMRvy2eI9boXMJ92WypSYeVkUKPRWD38hYy0xlCk39b2/RTDQOSggkvksEUgKW2afRhNz2DUZQ+Yv5Co906+zGVdo3TQdFO4CvBjhVMXXQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753711749; c=relaxed/simple; bh=bntmfnQRSd7WivA6jdNwOuhOpqOZyGEkf9XBJ6tCh9g=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=LLbwX3cJ/snY2V1HyAYz7HqReLvCmeRwhfs71JFy+tTNZlJyk7AhAVZDEDDSjnLpZ1NbHKXyHKt0FQRU5RpB9SX9bw5rlesZfLgvkbsyLDf0ZPK57ZPZ1uval+5S3exPyFzZ9MPVRxRsPKbBzhOAFsg14BhSAVA8nCXjBaJ/w6I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=IuzBxFO3; 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="IuzBxFO3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BBF39C4CEE7; Mon, 28 Jul 2025 14:09:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1753711748; bh=bntmfnQRSd7WivA6jdNwOuhOpqOZyGEkf9XBJ6tCh9g=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=IuzBxFO3odfe1zTxmYpXwab2K9nGNmL4Hc1qA5TkS496oh1rekcf/mvh6f2gfXkHa Egx4B0+CX8F/In9nY71idGFzgaEdNB2v/W3O9zmzh4lLSNqYLdMa/dggV4QqSHUbCJ xPadUj345sS8fSvpRJp/AlDv5bLWjBEsEPQ+iOfSPcsZbjeB6iwolow7slqBDV+PUA HuA8Crwxm/lfn3I9/Moq1Q04cZY+Z/Uuoam97PPBQzZK2Xrx/aM3Q0DF1Yb20BTLKB ZEBLpfA7A8wCVFMPkGQO/kT/+rrqvyg+lW7airbI309UDOh62KnDpibV304qQNLQOf WmNnwEiOS+GOA== Message-ID: Date: Mon, 28 Jul 2025 16:09:05 +0200 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: FAILED: patch "[PATCH] mptcp: make fallback action and fallback decision atomic" failed to apply to 5.15-stable tree Content-Language: en-GB, fr-BE To: gregkh@linuxfoundation.org, pabeni@redhat.com, kuba@kernel.org Cc: stable@vger.kernel.org References: <2025072147-privatize-stallion-5438@gregkh> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Greg, On 21/07/2025 12:55, gregkh@linuxfoundation.org wrote: > > The patch below does not apply to the 5.15-stable tree. > If someone wants it applied there, or to any other stable or longterm > tree, then please email the backport, including the original git commit > id to . (...) > ------------------ original commit in Linus's tree ------------------ > > From f8a1d9b18c5efc76784f5a326e905f641f839894 Mon Sep 17 00:00:00 2001 > From: Paolo Abeni > Date: Mon, 14 Jul 2025 18:41:44 +0200 > Subject: [PATCH] mptcp: make fallback action and fallback decision atomic > > Syzkaller reported the following splat: (...) > Since we need to track the 'fallback is possible' condition and the > fallback status separately, there are a few possible races open between > the check and the actual fallback action. > > Add a spinlock to protect the fallback related information and use it > close all the possible related races. While at it also remove the > too-early clearing of allow_infinite_fallback in __mptcp_subflow_connect(): > the field will be correctly cleared by subflow_finish_connect() if/when > the connection will complete successfully. > > If fallback is not possible, as per RFC, reset the current subflow. > > Since the fallback operation can now fail and return value should be > checked, rename the helper accordingly. > > Fixes: 0530020a7c8f ("mptcp: track and update contiguous data status") FYI, I don't think backporting this commit f8a1d9b18c5e ("mptcp: make fallback action and fallback decision atomic") in v5.15 and v5.10 is worth it: triggering this warning is difficult and required admin rights. Plus the fix is quite invasive, and causes many conflicts in these versions. Same for commit def5b7b2643e ("mptcp: plug races between subflow fail and subflow creation") for v5.15 only which depends on the other one. Cheers, Matt -- Sponsored by the NGI0 Core fund.