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SubjectRe: [RFC] prevent "dd if=/dev/mem" crash
Bjorn Helgaas <bjorn.helgaas@hp.com> 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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