FreeBSD and ELF GNU_STACK segment readable

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MaoKo

Joined: 07 May 2019
Posts: 100
Location: Paris/French

MaoKo 11 Dec 2019, 04:25

Hello!! I think there is a problem with read only stack in FreeBSD.
On my machine the OS literally hangup. I can't shutdown it properly.
Even with this simple snippet:

Code:

format ELF64 executable $09
entry _start
segment executable readable
_start:
  mov rax, $01
  xor rdi, rdi
  syscall
segment gnustack readable

This seem to also affect 32-bits binary. My FreeBSD is currently at version 12.0.
But I've tested on 11.2 and the system hang too when I try to reboot it.
If anyone known about this. Hope this might help Smile

11 Dec 2019, 04:25

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20333
Location: In your JS exploiting you and your system

revolution 11 Dec 2019, 04:28

I think it should be reported to the FreeBSD devs.

11 Dec 2019, 04:28

MaoKo

Joined: 07 May 2019
Posts: 100
Location: Paris/French

MaoKo 11 Dec 2019, 04:36

Yes you are right. But I'm not sure if it's really a bug. And read only stack segment is not easily generated by gcc/clang. I try to prevent fasm user of this. But yeah, I will try to report this as soon as possible Smile

11 Dec 2019, 04:36

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20333
Location: In your JS exploiting you and your system

revolution 11 Dec 2019, 04:41

It looks like a bug to me. It shouldn't be possible for a user program to create a denial-of-service (aka a hang) for the entire system.

11 Dec 2019, 04:41

guignol

Joined: 06 Dec 2008
Posts: 763

guignol 11 Dec 2019, 11:51

11 Dec 2019, 11:51

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