From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: References: <1448746350-19998-1-git-send-email-mic@digikod.net> <1448746350-19998-2-git-send-email-mic@digikod.net> <565A1F49.3040408@nod.at> <565A3035.6030104@digikod.net> <565A30DB.1070902@nod.at> <565A3228.5080908@digikod.net> From: Richard Weinberger Message-ID: <565A34AB.5010303@nod.at> Date: Sun, 29 Nov 2015 00:11:39 +0100 MIME-Version: 1.0 In-Reply-To: <565A3228.5080908@digikod.net> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Sender: linux-kernel-owner@vger.kernel.org Subject: Re: [PATCH 1/2] um: Set secure access mode for temporary file To: =?UTF-8?Q?Micka=c3=abl_Sala=c3=bcn?= , linux-kernel@vger.kernel.org Cc: Jeff Dike , Tristan Schmelcher , Greg Kroah-Hartman , user-mode-linux-devel@lists.sourceforge.net, user-mode-linux-user@lists.sourceforge.net List-ID: Am 29.11.2015 um 00:00 schrieb Micka=C3=ABl Sala=C3=BCn: >=20 >=20 > On 28/11/2015 23:55, Richard Weinberger wrote: >> Am 28.11.2015 um 23:52 schrieb Micka=C3=ABl Sala=C3=BCn: >>> >>> On 28/11/2015 22:40, Richard Weinberger wrote: >>>> Am 28.11.2015 um 22:32 schrieb Micka=C3=ABl Sala=C3=BCn: >>>>> Replace the default insecure mode 0777 with 0700 for temporary fi= le. >>>>> >>>>> Prohibit other users to change the executable mapped code. >>>> >>>> Hmm, isn't the tmp file already unlinked at this stage? >>>> >>> >>> Yes, but if someone could open it before the unlink e.g. because of= the umask (which does not seems to be the case thanks to mkstemp, but = remains unspecified [1]), this user should then be able to have write a= ccess to the file descriptor/description. >> >> Yes, someone can open it before the unlink. But you change the file = mode after that. >> How does it improve the situation? The attacker has already the file= handle. >=20 > The attacker could have the file handle only in a read-only mode, whi= ch is a bit different than being able to write and execute arbitrary co= de thanks to a file descriptor mapped RWX :) =46air point. Please describe this in detail in the patch changelog. :-= ) Thanks, //richard -- To unsubscribe from this list: send the line "unsubscribe linux-kernel"= in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/