Re: Filling holes in ext2

From: Adrian Cox (adrian@humboldt.co.uk)
Date: Wed Aug 22 2001 - 13:59:57 EST


Andrew Morton wrote:
> Adrian Cox wrote:

>>Can this actually be exploited? I assume the test on __copy_from_user()
>>is there in case another thread changes memory mappings while
>>generic_file_write() is running. My attempts to do this haven't yet
>>succeeded.
> I'd expect it to occur if you simply pass an unmapped address
> to write()?

No, because the first thing generic_file_write does is an access_ok()
check. It can only happen if the permissions change during the function.
That's why it's hard to exploit for real.

-- 
Adrian Cox   http://www.humboldt.co.uk/

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