On 06/06/2020 20:39, Michael Kerrisk (man-pages) wrote:
On Sat, 6 Jun 2020 at 20:32, Jakub Wilk <jwilk@xxxxxxxxx> wrote:
* Jonny Grant <jg@xxxxxxxx>, 2020-06-06, 16:45:
3) Could i ask to clarify my understanding. For this "The binary
being executed by the process does not have read permission enabled."
-- is this when the binary permissions are changed after it starts
running?
No, AFAICS the permission check is done when the process starts.
How can the process start if the binary file doesn't have read
permissions enabled?
It's a bit weird, but the kernel doesn't mind:
$ cp /bin/ls .
$ chmod a-r ls
$ ./ls -l ls
--wx--x--x 1 jwilk jwilk 138856 Jun 6 20:22 ls
And from core(5):
There are various circumstances in which a core dump file is not
produced:
...
* The binary being executed by the process does not have read
permission enabled.
So, the binary can be executed, but not read, and will not do a core
dump (since that might be readable).
Thanks,
Michael
Hi Michael, Jakub,
It sounds like a good security feature. Could that be documented on the man page as the reason?
ie something like this:
* The binary being executed by the process does not have read
permission enabled, therefore a core file would reveal information in a readable file, so it cannot be dumped.
Cheers
Jonny
