Re: 2.6.8.1-mm4

[Alan Cox]

On Llu, 2004-08-23 at 19:21, Tomasz Torcz wrote:
> >- This kernel has an x86 patch which alters the copy_*_user() functions so
> >  they will return -EFAULT on a fault rather than the number of bytes which
> >  remain to be copied.  This is a bit of an experiment, because this seems to
> >  be the preferred API for those functions.   It's a see-what-breaks thing.
> >
> 
>  Things appear to broke. Sometimes kernel starts to spit page allocation
> failures into log for few minutes, despite memory beeing available:

The kernel relies on copy_from_user returning the number of bytes copied
so no suprise there. In fact if it returns -EFAULT and you've not
reworked all the drivers (including out of kernel serial drivers in
particular) you get a security hole because you can move the buffer
pointers backwards.

Other code uses it to decide what object was passed for compatibility
too.

Alan


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