Re: copy_from_user

--- Amol Kumar Lad <amolk@ishoni.com> wrote:

  Suppose kernel tries to do copy_from_user from a pointer
that does not have any mapping. i.e. not in any VMA (and not

in

 stack area too..). 
Now (for 1386)
access_ok --> __range_ok
Suppose the 'from' ptr is within range then how kernel is
making sure that 'from' is invalid ??
The page fault handler will see that 'from' has no mapping and
it will die.. 

 
I believe this is handled using the 'fixup' code in
__copy_user_zeroing().
I don't understand the code well though, but I do know that it
works :)

-Ravi.

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