From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2364FC433DF for ; Fri, 17 Jul 2020 00:14:34 +0000 (UTC) Received: from shelob.surriel.com (shelob.surriel.com [96.67.55.147]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 864AB206F4 for ; Fri, 17 Jul 2020 00:14:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=systemli.org header.i=@systemli.org header.b="2lY02hsx" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 864AB206F4 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=systemli.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernelnewbies-bounces@kernelnewbies.org Received: from localhost ([::1] helo=shelob.surriel.com) by shelob.surriel.com with esmtp (Exim 4.94) (envelope-from ) id 1jwE0j-0002CU-T0; Thu, 16 Jul 2020 20:13:57 -0400 Received: from mail1.systemli.org ([2c0f:f930:0:5::214]) by shelob.surriel.com with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94) (envelope-from ) id 1jwE0i-0002CM-33 for Kernelnewbies@kernelnewbies.org; Thu, 16 Jul 2020 20:13:56 -0400 To: kernelnewbies DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=systemli.org; s=default; t=1594944829; bh=bqLnqb6rnspwBBgb46hhBXYzM2u09hXvDYrY6LkRsxI=; h=To:From:Subject:Date:From; b=2lY02hsxMs5b+5bpJbZee3juVgOzN8P/sTsdysnmPVW6ZsyTbldN5ud3AAy+sBn0q g8rmpgPP3SbyetMP7Tu7Yj47MGvapIv5rHfI3mLLT/l9/iEi+cN8B5WxWb/LbUdq7j /g8dj1PvAaFsl2eOxFWo2XnyeGIYiLbPllfQKWDyS8Exz2V2xgEEj883uAmj2ZKSKB ljhWJPLO/PPG7kcKehurZNK6bBBr3aKuwM/Wq9mB0q+gBj2VExcEZEkiGzlLkXUMGs i30NZyaHFevKSb4oNifDg4wZS8EnGZFLzQ9dZBx2kduyS9YCZ2ANQYvvvfq9HJekrZ 0piyjuhx6G/dQ== From: Richard Sailer Autocrypt: addr=richard_siegfried@systemli.org; prefer-encrypt=mutual; keydata= mQENBE3hr2UBCACos1E12camcYIlpe25jaqwu+ATrfuFcCIPsLmff7whzxClsaC78lsxQ3jD 4MIlOpkIBWJvc4sziai1P/CrafvM0DTuUasCv+mQpup6cFMWy1JmDtJ8X0Ccy/PH83e9Yjnv xJu0NhoQAqMZrVmXx4Q7DKcgpvkk9Oyd5u6ocfdb2GhF0Bxa7GySZyYOc4rQvduRLOdNMbnS 6SM+cTAhMOHtoqKWCP4EogXKALg6LDFcx8yUoMzLRy/YXsnWa1/WayG8Zr6kX84VKhTGUrdG Pw4Zg1cQ6vqwMZ4RwaR/9RWK2WnYr7XyOTDBgmCix5c5lu+GeLqUYUIPTvdQ7Xgwx0UhABEB AAG0OVJpY2hhcmQgU2llZ2ZyaWVkIFNhaWxlciA8cmljaGFyZF9zaWVnZnJpZWRAc3lzdGVt bGkub3JnPokBVwQTAQgAQQIbIwULCQgHAgYVCAkKCwIEFgIDAQIeAQIXgAIZARYhBAYAIbmK zp5fVAuyN/ZBOcwFm+HhBQJanueLBQkSYNKmAAoJEPZBOcwFm+Hh+ugH/2P0yClrZkkMK5y2 L389qNPlF8i1H77S4NE9zxiHI38jnIFLqjD4F+KzGAXNmOXCw+QYqLL+TmsuGY+5LOLtp/M4 lG6ajVC1JCcF2+bQrDc11g7AG7A+rySX5JpqSFO7ARfLTs3iW1DoyLN7lBUtL9dV+yx9mRUv fx/TcB9ItPhK4rtJuWy3yg6SNBZzkgc0zsCyIkJ4dEtdEW6IgW6Qk242kMVya8fytM02EwEM vBTdca/duCO2tEComPeF+8WExM+BfQ+6o3kpqRsOR6Ek6wDsnalFHy8NHaicbEy7qjybGOKZ IdvzAyAhsmpu+5ltOfQWViNBseqRk1H9ikuTKTq5AQ0ETeGvZQEIANRmPSJX9qVU+Hi74uvD /LYC3wPm5kCAS0Q5jT3AC5cisu8z92b/Bt8DRKwwpu4esZisQu3RSFvnmkrllkuokSAVKxXo bZG2yTq+qecrvKtVH99lA0leiy5TdcJdmhJvkcQv7kvIgKYdXSW1BAhUbtX827IGAW1LCvJL gKqox3Ftxpi5pf/gVh7NFXU/7n6Nr3NGi5havoReeIy8iVKGFjyCFN67vlyzaTV6yTUIdrko StTJJ8c7ECjJSkCW34lj8mR0y9qCRK5gIZURf3jjMQBDuDvHO0XQ4mog6/oOov4vJRyNMhWT 2b0LG5CFJeOQTQVgfaT1MckluRBvYMZAOmkAEQEAAYkBPAQYAQIAJgIbDBYhBAYAIbmKzp5f VAuyN/ZBOcwFm+HhBQJanueQBQkSYNKrAAoJEPZBOcwFm+HhrCAH/2doMkTKWrIzKmBidxOR +hvqJfBB4GvoHBsQoqWj85DtgvE5jKc11FYzSDzQjmMKIIBwaOjjrQ8QyXm2CYJlx7/GiEJc F3QNa5q3GBgiyZ0h78b2Lbu/sBhaCFSXHfnriRGvIXqsxyPMllqb+LBRy56ed97OQBQX8nFI umdUMtt8EFK2SM0KYY1V0COcYqGHMRUiVosTV1aVwoLm2SXsB9jicPUaQbRgsPfglTn00wnl fhJ8bAO800MtG+LW6pzP+6EZPvnHhKBS7Xbl6bn6r2OW32T7TeFg0RJbpE/MW1gY0NjgmtWj vdhuvK9nHCRL2O/xLofm9aoELUaXGHoxMn4= Subject: Dubios pointer casting with put_user() Message-ID: Date: Fri, 17 Jul 2020 02:13:34 +0200 MIME-Version: 1.0 X-BeenThere: kernelnewbies@kernelnewbies.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Learn about the Linux kernel List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: multipart/mixed; boundary="===============5580064190048219153==" Errors-To: kernelnewbies-bounces@kernelnewbies.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --===============5580064190048219153== Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="vdJb6BACpFA03hQSAJXt0GVjF1Eh51GEr" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --vdJb6BACpFA03hQSAJXt0GVjF1Eh51GEr Content-Type: multipart/mixed; boundary="XqTv7JKxZNR0aUQOmOUjxVf0dk3utgAdX"; protected-headers="v1" From: Richard Sailer To: kernelnewbies Message-ID: Subject: Dubios pointer casting with put_user() --XqTv7JKxZNR0aUQOmOUjxVf0dk3utgAdX Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable Hi, In the following example from net/dccp/proto.c the pointer given put_user() is casted to (int __user *) although the value to copy is a unsigned long. Is this (correctness and security wise) sane? Because as I understand it put_user() determines the amount it copies from the pointer type. ``` unsigned long amount =3D 0; skb =3D skb_peek(&sk->sk_receive_queue); if (skb !=3D NULL) { amount =3D skb->len; } rc =3D put_user(amount, (int __user *)arg); ``` Also skb->len is an unsigned int realisticly in most cases < 9000 (and in all cases I can imagine < int_max (with 16 bit)). I would like to declare amount as int outside of the switch case statement (because I need it in another case statement as signed int) would it be safe to do so? Thanks, -- Richard --XqTv7JKxZNR0aUQOmOUjxVf0dk3utgAdX-- --vdJb6BACpFA03hQSAJXt0GVjF1Eh51GEr Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCgAdFiEEBgAhuYrOnl9UC7I39kE5zAWb4eEFAl8Q7TsACgkQ9kE5zAWb 4eGNeAf/aJctJruEUTggSRxncmK4H9wuS+kM1iqZd1Fe3Jvz3I8X7cRmwcr7wIqT KeWGCAZ/VYz7dPMETKCUSKdDLa/LXeu1FLlhcqVjkBq8V7vr12TNILRi2wbQWHlz A3pdxf0b6TdkxjWztohH8k9cczEX4DZIVAKq/+bJcDl7YzfaISAUWmmbTYRN28+y J6PWpzDGoj7+2qsX65ERWl8kCgAUvwER04RRl8AkIKSWEfNtxmYZkOkZczewwkqn +SBOHv4h0INql5yawZTe6CQIR3Jm+kZoBGZ77jFRlq9FdenFnfODZ820BD1ZqvWn UMTOlOZupgxpIM+sfkTKNOw1EbZ+tA== =eYpy -----END PGP SIGNATURE----- --vdJb6BACpFA03hQSAJXt0GVjF1Eh51GEr-- --===============5580064190048219153== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies --===============5580064190048219153==--