From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 A5FBB3D9DAA for ; Wed, 26 Aug 2026 13:51:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787752272; cv=none; b=jOeHhcSOOHE9udrtH5b0X88VYtWOSUYOyfA7nCflHlX0XEIKLP1Jfm556gIlzNnFy2errQhZw+R3I662e0eNLz5fbywJQ3XeedIV7tYzGgWiNsR6sVDmzqOGozJVel1Ork4NLqRw9m+kqwHtY71Tip8HexekINaAl8aySbwGOLU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787752272; c=relaxed/simple; bh=EAggK8nV5Qevq1hw873QHw2PSVs+o1gjVLk6Ir0/Lq8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=F0AK1J/ukB5SI+D9dwfIKgvahRLW+68V/6CS8qWUxMw4Z7ENTCXeEqkClntcvGriyDsLa5kyauJxaUtPo2nI9Xu8XBe2wcJ9ERDRIyEb13wCv5t0C2q6BQZUch2s/QxJOyxtOAuMf5BdRPvJP2/EDnvR91MXSu8mHTD5vfctoBk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=D2xQP8aT; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="D2xQP8aT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 065651F000E9; Wed, 26 Aug 2026 13:51:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787752270; bh=r/xucIGyurKTfaqWrRWnLEFX8ZL8cR2ttaYp7ybzhOs=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=D2xQP8aTMmlc1qdCmwVjyVadtgpn2XeSVU82WhsPZutU3cqrl+/hWCLdweAQr8L/u xXMo27llYD0d93umgjFcckWpzKbLl+bQe9/E7Y6ZeKcytaHURhf3KAHnzJUGz9L3oO 0V2qNpOqJEuvjxv/+2kUW6Yv8sbDNJ9pRQWAE3hCoAFfYKeAogxfXUDfAKu0n2njCF IjCOYc/YNmVgzd3OX6VOfKqd1dWQNkPAhbzEYwly99x4EwaEH5/OnPsSMkzzDwc3mK HXZ3JFbAUn05MiIvESNdwohWrFztuWut6MG0FdX0cIB6ht00EKfihmziOVMySLO7N4 srLesih/lm6rw== Message-ID: Date: Wed, 26 Aug 2026 15:51:07 +0200 Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [PATCH mptcp-net v3] mptcp: pm: userspace: unify entry free path via RCU callback Content-Language: fr To: Geliang Tang , mptcp@lists.linux.dev Cc: Geliang Tang References: From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Geliang, On 01/07/2026 08:11, Geliang Tang wrote: > From: Geliang Tang > > In mptcp_pm_nl_remove_doit(), sk_omem_alloc is decremented immediately > but the memory is freed later via kfree_rcu(). This allows a CAP_NET_ADMIN > user to bypass the socket memory quota and exhaust kernel memory by > accumulating RCU callbacks. > > Fix by using call_rcu() with a custom callback that uses sock_kfree_s() > to free the entry and decrement sk_omem_alloc atomically. To ensure the > socket remains valid until the callback runs, take a reference with > sock_hold() when storing the socket pointer in the entry, and release it > with sock_put() in the callback. > > Convert the synchronous freeing paths in free_local_addr_list() and > delete_local_addr() to use the same RCU callback, ensuring the socket > reference is properly released. > > Additionally, mptcp_userspace_pm_append_new_local_addr() now checks > SOCK_DEAD under the spinlock before allocating. A SYN+JOIN handler > holding an msk reference from mptcp_token_get_sock() could otherwise > race with __mptcp_destroy_sock() - sock_orphan() sets SOCK_DEAD and > then mptcp_userspace_pm_release() clears the list, so a new entry > allocated after that point would never be freed and its sock_hold() > would leak the msk permanently. (...) > diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h > index da40c6f3705f..250736eae0be 100644 > --- a/net/mptcp/protocol.h > +++ b/net/mptcp/protocol.h > @@ -257,6 +257,8 @@ struct mptcp_pm_addr_entry { > u32 flags; > int ifindex; > struct socket *lsk; > + struct sock *sk; Also, I don't think 'lsk' is used with the userspace PM: can we re-use it instead of adding a new one? (Or using an anonymous union?) > + struct rcu_head rcu; > }; > > struct mptcp_data_frag { Cheers, Matt -- Sponsored by the NGI0 Core fund.