From patchwork Wed Aug 9 10:41:42 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: 13347773 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 0A8151774D; Wed, 9 Aug 2023 11:00:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 68CB5C433CB; Wed, 9 Aug 2023 11:00:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1691578811; bh=dVBAkrIYNCNukXN1fuSFIY/HtrxN633d6BXx6ActWB8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=KGIgFWNRFmJseG0OVklQh1wNnayyLDrEvJ+LvRd0QNhs+EHLeosK8TG+l8jZlxp6/ Dpfa/6Rvmsy47XKDLefowMHrjj+bYYsaex5ybAp9VrOiEMtEFc75m+gsIiZ1NJ0usv sCUT2NS8t5dq6nYPM7qd7tAJvjpeaQOSJNxiVu9Y= 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 5.15 66/92] net: tap_open(): set sk_uid from current_fsuid() Date: Wed, 9 Aug 2023 12:41:42 +0200 Message-ID: <20230809103635.872225656@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230809103633.485906560@linuxfoundation.org> References: <20230809103633.485906560@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 5c9241f3ceab3257abe2923a59950db0dc8bb737 upstream. Commit 66b2c338adce initializes the "sk_uid" field in the protocol socket (struct sock) from the "/dev/tapX" 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 "tap", the action that creates the socket is open("/dev/tapX"). Therefore the device node's owner UID is irrelevant. In most cases, "/dev/tapX" will be owned by root, so in practice, commit 66b2c338adce 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/tapX" 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: 66b2c338adce ("tap: tap_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/tap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/net/tap.c +++ b/drivers/net/tap.c @@ -523,7 +523,7 @@ static int tap_open(struct inode *inode, q->sock.state = SS_CONNECTED; q->sock.file = file; q->sock.ops = &tap_socket_ops; - sock_init_data_uid(&q->sock, &q->sk, inode->i_uid); + sock_init_data_uid(&q->sock, &q->sk, current_fsuid()); q->sk.sk_write_space = tap_sock_write_space; q->sk.sk_destruct = tap_sock_destruct; q->flags = IFF_VNET_HDR | IFF_NO_PI | IFF_TAP;