Re: [RFC] prevent "dd if=/dev/mem" crash

[Andrew Morton]

Bjorn Helgaas <bjorn.helgaas@xxxxxx> wrote:
>
> Old behavior:
> 
>     # dd if=/dev/mem of=/dev/null
>     <unrecoverable machine check>

I recently fixed this for ia32 by changing copy_to_user() to not oops if
the source address generated a fault.  Similarly copy_from_user() returns
an error if the destination generates a fault.

In other words: drivers/char/mem.c requires that the architecture's
copy_*_user() functions correctly handle faults on either the source or
dest of the copy.

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