From: "Mickaël Salaün" <mic@digikod.net>
To: Richard Weinberger <richard@nod.at>, linux-kernel@vger.kernel.org
Cc: Jeff Dike <jdike@addtoit.com>,
Tristan Schmelcher <tschmelcher@google.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
user-mode-linux-devel@lists.sourceforge.net,
user-mode-linux-user@lists.sourceforge.net
Subject: Re: [PATCH 1/2] um: Set secure access mode for temporary file
Date: Sun, 29 Nov 2015 00:00:56 +0100 [thread overview]
Message-ID: <565A3228.5080908@digikod.net> (raw)
In-Reply-To: <565A30DB.1070902@nod.at>
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On 28/11/2015 23:55, Richard Weinberger wrote:
> Am 28.11.2015 um 23:52 schrieb Mickaël Salaün:
>>
>> 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.
>
> 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.
The attacker could have the file handle only in a read-only mode, which is a bit different than being able to write and execute arbitrary code thanks to a file descriptor mapped RWX :)
Mickaël
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next prev parent reply other threads:[~2015-11-29 0:20 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-28 21:32 [PATCH 0/2] um: Protect memory mapped file Mickaël Salaün
2015-11-28 21:32 ` [PATCH 1/2] um: Set secure access mode for temporary file Mickaël Salaün
2015-11-28 21:40 ` Richard Weinberger
2015-11-28 22:52 ` Mickaël Salaün
2015-11-28 22:55 ` Richard Weinberger
2015-11-28 23:00 ` Mickaël Salaün [this message]
2015-11-28 23:11 ` Richard Weinberger
2015-11-28 21:32 ` [PATCH 2/2] um: Use race-free temporary file creation Mickaël Salaün
2015-11-28 22:07 ` Richard Weinberger
2015-11-28 22:56 ` Mickaël Salaün
2015-11-28 22:59 ` Richard Weinberger
2015-11-28 23:02 ` Mickaël Salaün
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