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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A27C5CD6E77 for ; Wed, 11 Oct 2023 14:44:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232246AbjJKOoV (ORCPT ); Wed, 11 Oct 2023 10:44:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39072 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235050AbjJKOoU (ORCPT ); Wed, 11 Oct 2023 10:44:20 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0C0B39D; Wed, 11 Oct 2023 07:44:19 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5DFCEC433C8; Wed, 11 Oct 2023 14:44:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1697035458; bh=+yR23TOJN+Xmz9Lb4zxvgkbSPWcLWaKrsKLjuBEPNzc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=mX7iLpEAk08MdoBBF+GxGElmoNo1IzYjHSOr3HjcdmOkdQdpZ0YUWGCpHVLlSBrwN gUpkhOXDWfaUBnJfBEWaUqIJ0CbNEdhPDTlSqYHh9KfYWQRj28Zbq2pA66bEtlDjOc jwa6ACSID0JMi7CzCyAZbdsuSrG9Z9So5TUYe6WlCJkCXncdykvYTL4HTHQHk7sESG VI0MrlvkHormwraSdBvdtUZZCLc0vcsFycICZFqrTG2u6qKdkTaPschD4NphQ2tb11 kaF1jCRXY2uT6TJKU2sq5Wj5q2j8J+PE9VpU1qK2f2PYB5mMLMDY0+e+E7sfLb8aFV mmGRg+kn5BwAQ== Date: Wed, 11 Oct 2023 16:44:14 +0200 From: Alejandro Colomar To: Matthew House Cc: Rik van Riel , linux-man@vger.kernel.org, LKML , kernel-team@meta.com, Eric Biederman Subject: Re: [PATCH] execve.2: execve also returns E2BIG if a string is too long Message-ID: References: <20231010234153.021826b1@imladris.surriel.com> <60b4d916663ea31ae05a958b6dea8aa5bf740d0a.camel@surriel.com> <20231011134437.750422-1-mattlloydhouse@gmail.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="w7jaJI5jMx6pA59R" Content-Disposition: inline In-Reply-To: <20231011134437.750422-1-mattlloydhouse@gmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-man@vger.kernel.org --w7jaJI5jMx6pA59R Content-Type: text/plain; protected-headers=v1; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Date: Wed, 11 Oct 2023 16:44:14 +0200 From: Alejandro Colomar To: Matthew House Cc: Rik van Riel , linux-man@vger.kernel.org, LKML , kernel-team@meta.com, Eric Biederman Subject: Re: [PATCH] execve.2: execve also returns E2BIG if a string is too long Hi Matthew, On Wed, Oct 11, 2023 at 09:44:29AM -0400, Matthew House wrote: >=20 > To expand on this, there are basically two separate byte limits in > fs/exec.c, one for each individual argv/envp string, and another for all > strings and all pointers to them as a whole. To put the whole thing in > pseudocode, the checks work effectively like this, assuming I haven't made > any errors: >=20 > int argc, envc; > unsigned long bytes, limit; >=20 > /* assume that argv has already been adjusted to add an empty argv[0] */ > argc =3D 0, envc =3D 0, bytes =3D 0; > for (char **a =3D argv; *a !=3D NULL; a++, argc++) { > if (strlen(*a) >=3D MAX_ARG_STRLEN) > return -E2BIG; > bytes +=3D strlen(*a) + 1; > } > for (char **e =3D envp; *e !=3D NULL; e++, envc++) { > if (strlen(*e) >=3D MAX_ARG_STRLEN) > return -E2BIG; > bytes +=3D strlen(*e) + 1; > } >=20 > if (argc > MAX_ARG_STRINGS || envc > MAX_ARG_STRINGS) > return -E2BIG; > bytes +=3D (argc + envc) * sizeof(void *); >=20 > limit =3D max(min(_STK_LIM / 4 * 3, rlim_stack.rlim_cur / 4), ARG_MAX); > if (bytes > limit) > return -E2BIG; >=20 > Thank you, > Matthew House Thanks! This thing would be useful in the commit message. An example program demonstrating it would be even better. Cheers, Alex --=20 --w7jaJI5jMx6pA59R Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEE6jqH8KTroDDkXfJAnowa+77/2zIFAmUmtL4ACgkQnowa+77/ 2zJjZxAAqrH8dlVZ8bDdOzaxordiMlVbUvj6UcexmDlle29byjFVQcjgJfmvHh18 6o+bIav3sizGh7ht1vhj7+x0673z6K5d8/QlhrBkqB5Qunx4YgpiaXrpOPOYt3gf trS4lkbxrI9WU0ifT0A7HeVz3KQlNXmtyUlue4N4kH6b92KZnpdDtStnnHSWwuco Uf+R66ir8+lWjhXNI5IpplYiQz3SFAo/9ztjwxHXesVSbpnqwCVD6oP6dL+dc0W1 B7PreIcJmn+HykjX1hk8Y4+FIqWdP0tJZ4Tv7JSeR653grEFsQhc9bzenNg2+kvd ymz8gDoGwpgbEfLIH6G/MLXShU+7PGmcYEYjev1WBGEeZg1BY1DqUUi4VnZAWL4Y 0dno5do4fd0stjNL3vM7JBU6iCZ2reaoV6yMBbs4Wi4vsix19A+o0ds/aIMGF2iA +z/ti1HEsm8lXs6D7U5nusj/F6ZeNMyQWpXV7K1CUX+vzZCMuEXx80vf1FeWNMEI V/bOCYPd6AjQaQ/Ox4HBzi5gnATNvPhiLCkQnkKwZTi501sQhIIBU3IbnvT7z8dW F7phHREEszDVQSAckPHsatmQ/LdLNtBpJA9JVlj1YavTlIORlTDmmOIQJtZNlgL6 F4XLvPvDMMFozKjIhBsAcoGI5sWXlhDKW5m1I2jdv+A31pUFDCg= =zFqm -----END PGP SIGNATURE----- --w7jaJI5jMx6pA59R--