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Flash write crash at NULL + 0x2b288 (on 64-bit) #131

Closed GoogleCodeExporter closed 9 years ago

GoogleCodeExporter commented 9 years ago 
A PoC is attached. This is a fuzz test case so it's not immediately obvious 
what is going on, but it is a reliable and consistent test case on Pepper Flash 
Chrome (Linux x64 confirmed).

When the crash triggers, this is the instruction:

movb   $0x1,0x2b288(%rax)

At the time of the crash %rax == 0.

However, it's possible to get the address 0x2b288 mapped in modern operating 
systems, because "NULL mapping" protections typically only cover the first 64kb 
(Windows, Linux) or not at all (Mac OS X 32-bit).

It's unlikely that malicious actionscript will be able to map anything so low 
on 64-bit, but 32-bit will be an issue.

This bug is subject to a 90 day disclosure deadline. If 90 days elapse
without a broadly available patch, then the bug report will automatically
become visible to the public.

Original issue reported on code.google.com by cev...@google.com on 21 Oct 2014 at 12:09

Attachments:

GoogleCodeExporter commented 9 years ago 
Small correction regarding NULL mapping protections on OS X: the default linker 
options on OS X will insert a 1 page __PAGEZERO section with a fixed mapping at 
0 and --- protection, so userspace dereferences of any pointer to addresses on 
the NULL page aren't exploitable. 0x2b288 falls well outside that and it would 
be application specific if it were exploitable or not.

32 bit OS X processes allow native code to change the protection of that NULL 
page mapping at runtime and therefore exploit *kernel* NULL pointer 
dereferences - this is the fundamental difference to say linux where you need 
to be root to lower mmap_min_addr and exploit a kernel NULL pointer dereference.

Original comment by ianb...@google.com on 21 Oct 2014 at 10:11

GoogleCodeExporter commented 9 years ago

Original comment by cev...@google.com on 8 Nov 2014 at 2:37

GoogleCodeExporter commented 9 years ago 
http://helpx.adobe.com/security/products/flash-player/apsb14-24.html

Original comment by cev...@google.com on 20 Nov 2014 at 1:28