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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