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 1C0E43783CF; Tue, 17 Feb 2026 20:43:58 +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=1771361038; cv=none; b=U3KMypXUyhazws6wxl/PFmXvhJFB3NuN+yRsB4328TUCZmawXjViyAJWYsITH7a0IOZ2XFzYAoxRK01SgzwtyeBnw4g2GYFZ1ix/Ng9ilV0lDzuV30IjHgowFO7uhcg/Svv64dLjsSKp2nm8WT+qja1ORekTxsyncdldPhbzsRU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771361038; c=relaxed/simple; bh=2SQMWTfzJck1d9ZeXXc6I//KDaqGCU5XFhEe5drB+eU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=bwmfg3auLhuOPI1CmP49gCMbENcMV0wFhCAdVA4Jforu7OyVxGsOxWYCGANyB4C3SqWZB3OOZRFR3BqcBc8S3v9Mv4uHLdqI7Ce7ykc62azviCtFyJhBkaR7wBQH2uLEiGrJxx7EoVo3uh+tD+GHaB8aQ3ox8dNUvVkinscHAgA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=u1tmR58s; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="u1tmR58s" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 81ED2C4CEF7; Tue, 17 Feb 2026 20:43:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1771361038; bh=2SQMWTfzJck1d9ZeXXc6I//KDaqGCU5XFhEe5drB+eU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=u1tmR58sKhYCt0gpadfB2dqTpPp5+/vmif5ArhXjUzTrSEgJC0xyEA8sbOjiuFEno G3ZaGdoshH3zF6PX2b+3JstF5Z5RZ4ZLWQB92ftU/k06mtXeX6STnjLVqwoz+8vWOH /KpIVZzyazSsQqBReRXeEmbO/il0HDZhu3bHo1Rc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Eric Dumazet , syzbot+5498a510ff9de39d37da@syzkaller.appspotmail.com, Eulgyu Kim , Mat Martineau , "Matthieu Baerts (NGI0)" , Jakub Kicinski Subject: [PATCH 5.15 22/39] mptcp: fix race in mptcp_pm_nl_flush_addrs_doit() Date: Tue, 17 Feb 2026 21:31:31 +0100 Message-ID: <20260217200003.785026394@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260217200002.929083107@linuxfoundation.org> References: <20260217200002.929083107@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet commit e2a9eeb69f7d4ca4cf4c70463af77664fdb6ab1d upstream. syzbot and Eulgyu Kim reported crashes in mptcp_pm_nl_get_local_id() and/or mptcp_pm_nl_is_backup() Root cause is list_splice_init() in mptcp_pm_nl_flush_addrs_doit() which is not RCU ready. list_splice_init_rcu() can not be called here while holding pernet->lock spinlock. Many thanks to Eulgyu Kim for providing a repro and testing our patches. Fixes: 141694df6573 ("mptcp: remove address when netlink flushes addrs") Signed-off-by: Eric Dumazet Reported-by: syzbot+5498a510ff9de39d37da@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/6970a46d.a00a0220.3ad28e.5cf0.GAE@google.com/T/ Reported-by: Eulgyu Kim Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/611 Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260124-net-mptcp-race_nl_flush_addrs-v3-1-b2dc1b613e9d@kernel.org Signed-off-by: Jakub Kicinski [ Conflicts because the code has been moved from pm_netlink.c to pm_kernel.c later on in commit 8617e85e04bd ("mptcp: pm: split in-kernel PM specific code"). The same modifications can be applied in pm_netlink.c with one exception, because 'pernet->local_addr_list' has been renamed to 'pernet->endp_list' in commit 35e71e43a56d ("mptcp: pm: in-kernel: rename 'local_addr_list' to 'endp_list'"). The previous name is then still being used in this version. Also, another conflict is caused by commit 7bcf4d8022f9 ("mptcp: pm: rename helpers linked to 'flush'") which is not in this version: mptcp_nl_remove_addrs_list() has been renamed to mptcp_nl_flush_addrs_list(). The previous name has then been kept. ] Signed-off-by: Matthieu Baerts (NGI0) Signed-off-by: Greg Kroah-Hartman --- net/mptcp/pm_netlink.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) --- a/net/mptcp/pm_netlink.c +++ b/net/mptcp/pm_netlink.c @@ -1656,16 +1656,26 @@ static void __reset_counters(struct pm_n static int mptcp_nl_cmd_flush_addrs(struct sk_buff *skb, struct genl_info *info) { struct pm_nl_pernet *pernet = genl_info_pm_nl(info); - LIST_HEAD(free_list); + struct list_head free_list; spin_lock_bh(&pernet->lock); - list_splice_init(&pernet->local_addr_list, &free_list); + free_list = pernet->local_addr_list; + INIT_LIST_HEAD_RCU(&pernet->local_addr_list); __reset_counters(pernet); pernet->next_id = 1; bitmap_zero(pernet->id_bitmap, MAX_ADDR_ID + 1); spin_unlock_bh(&pernet->lock); - mptcp_nl_remove_addrs_list(sock_net(skb->sk), &free_list); + + if (free_list.next == &pernet->local_addr_list) + return 0; + synchronize_rcu(); + + /* Adjust the pointers to free_list instead of pernet->local_addr_list */ + free_list.prev->next = &free_list; + free_list.next->prev = &free_list; + + mptcp_nl_remove_addrs_list(sock_net(skb->sk), &free_list); __flush_addrs(&free_list); return 0; }