From patchwork Wed Aug 9 10:41:10 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 13347770 X-Patchwork-Delegate: kuba@kernel.org 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 7A40E613A; Wed, 9 Aug 2023 10:55:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EFF75C433C8; Wed, 9 Aug 2023 10:55:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1691578502; bh=B1QedS+pB//tSBuJSmXwg7w1JvOxIlQtpHnhU9RrjF4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=O18Wm0Vv9GT9Z3XCEDzFXMVwZxf9H6JiVdSh7QmqrRwJfNKJcQotiTPYs9OPwD6CB LlH0f+jZND9itCLmgqGG995KCgD9ANDPCviRpXr7pWGHGle77QD4eGfh1bpZMgBD37 mA7W9KAZUeg3l4mGKdHyphOeQFf03YGeWmm+gzcI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Eric Dumazet , Lorenzo Colitti , Paolo Abeni , Pietro Borrello , netdev@vger.kernel.org, Laszlo Ersek , "David S. Miller" Subject: [PATCH 6.1 083/127] net: tun_chr_open(): set sk_uid from current_fsuid() Date: Wed, 9 Aug 2023 12:41:10 +0200 Message-ID: <20230809103639.406806992@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230809103636.615294317@linuxfoundation.org> References: <20230809103636.615294317@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: kuba@kernel.org From: Laszlo Ersek commit 9bc3047374d5bec163e83e743709e23753376f0c upstream. Commit a096ccca6e50 initializes the "sk_uid" field in the protocol socket (struct sock) from the "/dev/net/tun" device node's owner UID. Per original commit 86741ec25462 ("net: core: Add a UID field to struct sock.", 2016-11-04), that's wrong: the idea is to cache the UID of the userspace process that creates the socket. Commit 86741ec25462 mentions socket() and accept(); with "tun", the action that creates the socket is open("/dev/net/tun"). Therefore the device node's owner UID is irrelevant. In most cases, "/dev/net/tun" will be owned by root, so in practice, commit a096ccca6e50 has no observable effect: - before, "sk_uid" would be zero, due to undefined behavior (CVE-2023-1076), - after, "sk_uid" would be zero, due to "/dev/net/tun" being owned by root. What matters is the (fs)UID of the process performing the open(), so cache that in "sk_uid". Cc: Eric Dumazet Cc: Lorenzo Colitti Cc: Paolo Abeni Cc: Pietro Borrello Cc: netdev@vger.kernel.org Cc: stable@vger.kernel.org Fixes: a096ccca6e50 ("tun: tun_chr_open(): correctly initialize socket uid") Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2173435 Signed-off-by: Laszlo Ersek Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- drivers/net/tun.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -3457,7 +3457,7 @@ static int tun_chr_open(struct inode *in tfile->socket.file = file; tfile->socket.ops = &tun_socket_ops; - sock_init_data_uid(&tfile->socket, &tfile->sk, inode->i_uid); + sock_init_data_uid(&tfile->socket, &tfile->sk, current_fsuid()); tfile->sk.sk_write_space = tun_sock_write_space; tfile->sk.sk_sndbuf = INT_MAX;