linux-kernel - Re: [PATCH 1/2] um: Set secure access mode for temporary file

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Date:	Sat, 28 Nov 2015 23:52:37 +0100
From:	Mickaël Salaün <mic@...ikod.net>
To:	Richard Weinberger <richard@....at>, linux-kernel@...r.kernel.org
Cc:	Jeff Dike <jdike@...toit.com>,
	Tristan Schmelcher <tschmelcher@...gle.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	user-mode-linux-devel@...ts.sourceforge.net,
	user-mode-linux-user@...ts.sourceforge.net
Subject: Re: [PATCH 1/2] um: Set secure access mode for temporary file


On 28/11/2015 22:40, Richard Weinberger wrote:
> Am 28.11.2015 um 22:32 schrieb Mickaël Salaün:
>> Replace the default insecure mode 0777 with 0700 for temporary file.
>>
>> 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 access to the file descriptor/description.

 Mickaël

1. http://man7.org/linux/man-pages/man3/mkstemp.3.html#NOTES



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