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

[MickaÃl SalaÃn]

On 28/11/2015 23:55, Richard Weinberger wrote:
> Am 28.11.2015 um 23:52 schrieb MickaÃl SalaÃn:
>>
>> On 28/11/2015 22:40, Richard Weinberger wrote:
>>> Am 28.11.2015 um 22:32 schrieb MickaÃl SalaÃn:
>>>> 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 :)

 MickaÃl

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