From nobody Mon Mar 2 06:35:30 2026 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 7CB422E7635; Thu, 12 Feb 2026 15:06:13 +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=1770908773; cv=none; b=EqXTIJEytzVxnUYJM2xj3SOdvPsKhTUEtngZ3NeGydbJUNOjFL7+MLdyZVD9/n90a7WahohCkIp72NmOs9AqdmaXpJrGzwS129+6PZ/SgW8w8O5TsXh7PqrSAsMZjrrUCbXUnqH8NOMVg2ia3LA0v3XMu/3gDCCJx8ZaZ94Z+10= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770908773; c=relaxed/simple; bh=K7i/IEqYAIP3hwqfxxBGOuWS4B0xoeIJM9ICOS9WQ54=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=rUk6XyatihIsYWyodAFeRbvRh+DV40kTNy87Lqt2WXOSe4TL9lDbN7aWJS+7qMKvibwkHF03uQPYcrtLTBctPmf130M0DyngkCUgyOp4erTUU/urpRfodSvEXfLvFf0iUgYMYa7L34UQbKWOmdzHqXh35CVGZrLJL6Y6aLHWVd4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=d5BsC5DV; 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="d5BsC5DV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4854CC4CEF7; Thu, 12 Feb 2026 15:06:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770908772; bh=K7i/IEqYAIP3hwqfxxBGOuWS4B0xoeIJM9ICOS9WQ54=; h=From:To:Cc:Subject:Date:From; b=d5BsC5DVxypDBstvfFN4IbNmsOPxByal+71ukjnEdrKxA13EyXORz0zZNzVJEgesP 3rTyxcrQgIGmVmMPuzFy5A72NVWxw+mGh1gIcOkGpObNlkw5o1gd+f2K780q45bkuM ARtyTAyRJRsKFiCOKcY2c89clWtrnRqBhaNcGuau7CGtEePF2SCeJWGYGSYnKP7z0h 7sqZ54qJH533xxRSDqYpGQLsTk7uKUcj9F6Kn6eCi9GNdhmDYWFWT+Uj7mNOQkZRe9 /c/GqfSQpe6tWn/N+tUtbljGi683PEQlPvxiffHu1Ko3k44DMMUlts4xydGoaLIn+A pyVBCNw6k8gcA== From: "Matthieu Baerts (NGI0)" To: stable@vger.kernel.org, gregkh@linuxfoundation.org Cc: MPTCP Upstream , Eric Dumazet , syzbot+5498a510ff9de39d37da@syzkaller.appspotmail.com, Eulgyu Kim , Mat Martineau , "Matthieu Baerts (NGI0)" , Jakub Kicinski Subject: [PATCH 6.12.y] mptcp: fix race in mptcp_pm_nl_flush_addrs_doit() Date: Thu, 12 Feb 2026 16:05:48 +0100 Message-ID: <20260212150547.1345709-2-matttbe@kernel.org> X-Mailer: git-send-email 2.51.0 Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2925; i=matttbe@kernel.org; h=from:subject; bh=YxruUXO+vGA4F+8DkfEKookwW/IrvLpnYlr9D467xAA=; b=owGbwMvMwCVWo/Th0Gd3rumMp9WSGDJ73/gsF+K5VK6vvOOmudWqR9J22e1OZidWrLJbnLpcP /TY1dnTOkpZGMS4GGTFFFmk2yLzZz6v4i3x8rOAmcPKBDKEgYtTACai8p2RYWXwlf8rvW7eiZ14 nKHtwqvqxy+ZWHNOZVzMZHyucOHF888M/6NnMheU9i9+Edy5MtvaIG/O92l9T2ZpR+uXsX5JNw4 MYQYA X-Developer-Key: i=matttbe@kernel.org; a=openpgp; fpr=E8CB85F76877057A6E27F77AF6B7824F4269A073 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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@googl= e.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. ] Signed-off-by: Matthieu Baerts (NGI0) --- net/mptcp/pm_netlink.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c index 0b4ab3c816da..864c26e22b24 100644 --- a/net/mptcp/pm_netlink.c +++ b/net/mptcp/pm_netlink.c @@ -1811,16 +1811,26 @@ static void __reset_counters(struct pm_nl_pernet *p= ernet) int mptcp_pm_nl_flush_addrs_doit(struct sk_buff *skb, struct genl_info *in= fo) { struct pm_nl_pernet *pernet =3D genl_info_pm_nl(info); - LIST_HEAD(free_list); + struct list_head free_list; =20 spin_lock_bh(&pernet->lock); - list_splice_init(&pernet->local_addr_list, &free_list); + free_list =3D pernet->local_addr_list; + INIT_LIST_HEAD_RCU(&pernet->local_addr_list); __reset_counters(pernet); pernet->next_id =3D 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 =3D=3D &pernet->local_addr_list) + return 0; + synchronize_rcu(); + + /* Adjust the pointers to free_list instead of pernet->local_addr_list */ + free_list.prev->next =3D &free_list; + free_list.next->prev =3D &free_list; + + mptcp_nl_flush_addrs_list(sock_net(skb->sk), &free_list); __flush_addrs(&free_list); return 0; } --=20 2.51.0