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 B45F527702D; Wed, 4 Feb 2026 15:28:51 +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=1770218931; cv=none; b=k+oSGKvxSuyIBSt54YPUN9G+ZDiHUtkX8B4a6CAT2BTlZp4H0ZFhVUwRE0Zxmp5Aiylk4Z89dBpNMNHHMAq8j3kiv7kNzjFzC741mCNymfs0je6aqRkY9n2AH7zKfXU1TuB0lrlX1Z0gpWZ+6RZFQuo0LDphpNberNQ1hXXYJk0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770218931; c=relaxed/simple; bh=DqQp8pi4C0X8tZBe7LNLOU0eIqZ/zlaU0pRfSLAN7zY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=a0wU4xVregb5INp6ecaAsKJPH8Jvz12e3wkntJJ7W4QDyJYzF3DKmuQCvSy+vtCxVWnl3Sv9D4V01I03lbVPOHS5/DnhGEc8qneJLdM7CwJ89mvTFL5wu62+9OPTfltsop3aHWymPCvBETuuIalQf70P3RO/Q3M49WrpZJFU5Qg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=WfI4ItGF; 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="WfI4ItGF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 28C6CC4CEF7; Wed, 4 Feb 2026 15:28:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1770218931; bh=DqQp8pi4C0X8tZBe7LNLOU0eIqZ/zlaU0pRfSLAN7zY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WfI4ItGFITMvYRC5i7ghoQjJdhD3egs0xZnF+8nzlA4BU3HBkJ4a18cRFcDlFSEq5 KW8wQJxPwVTWKhVOj+T1YPQNrLTPtljZuWNhwGsUwj08DUUb7DwRlLR2inRXv17Evh hyiaifF1S6ips9/9JtHZSYp/XQA14g3Opd4hbptg= 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 , Sasha Levin Subject: [PATCH 6.18 017/122] mptcp: fix race in mptcp_pm_nl_flush_addrs_doit() Date: Wed, 4 Feb 2026 15:39:59 +0100 Message-ID: <20260204143852.486890750@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260204143851.857060534@linuxfoundation.org> References: <20260204143851.857060534@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 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit e2a9eeb69f7d4ca4cf4c70463af77664fdb6ab1d ] 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 Signed-off-by: Sasha Levin --- net/mptcp/pm_kernel.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/net/mptcp/pm_kernel.c b/net/mptcp/pm_kernel.c index 0a50fd5edc06d..1b517a81e0299 100644 --- a/net/mptcp/pm_kernel.c +++ b/net/mptcp/pm_kernel.c @@ -1276,16 +1276,26 @@ static void __reset_counters(struct pm_nl_pernet *pernet) int mptcp_pm_nl_flush_addrs_doit(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->endp_list, &free_list); + free_list = pernet->endp_list; + INIT_LIST_HEAD_RCU(&pernet->endp_list); __reset_counters(pernet); pernet->next_id = 1; bitmap_zero(pernet->id_bitmap, MPTCP_PM_MAX_ADDR_ID + 1); spin_unlock_bh(&pernet->lock); - mptcp_nl_flush_addrs_list(sock_net(skb->sk), &free_list); + + if (free_list.next == &pernet->endp_list) + return 0; + synchronize_rcu(); + + /* Adjust the pointers to free_list instead of pernet->endp_list */ + free_list.prev->next = &free_list; + free_list.next->prev = &free_list; + + mptcp_nl_flush_addrs_list(sock_net(skb->sk), &free_list); __flush_addrs(&free_list); return 0; } -- 2.51.0