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SubjectRe: [RFC][PATCH] kmemdup_from_user(): introduce
On Fri, Mar 06, 2009 at 04:27:53PM +0800, Li Zefan wrote:
> Alexey Dobriyan wrote:
> > On Fri, Mar 06, 2009 at 03:04:12PM +0800, Li Zefan wrote:
> >> I notice there are many places doing copy_from_user() which follows
> >> kmalloc():
> >>
> >> dst = kmalloc(len, GFP_KERNEL);
> >> if (!dst)
> >> return -ENOMEM;
> >> if (copy_from_user(dst, src, len)) {
> >> kfree(dst);
> >> return -EFAULT
> >> }
> >>
> >> kmemdup_from_user() is a wrapper of the above code. With this new
> >> function, we don't have to write 'len' twice, which can lead to
> >> typos/mistakes. It also produces smaller code.
> >
> > Name totally sucks, it mixes kernel idiom of allocation with purely
> > userspace function.
> >
>
> I'm not good at English, and I don't know why "kernel memory duplicated
> from user space" is so bad...
>
> or memdup_user() ?
>
> >> A qucik grep shows 250+ places where kmemdup_from_user() *may* be
> >> used. I'll prepare a patchset to do this conversion.
> >
> > 250?
> >
>
> I just found out how many copy_from_user() following km/zalloc(), so
> not all of them are replace-able.
>
> > Let's not add wrapper for every two lines that happen to be used
> > together.
> >
>
> Why not if we have good reasons? And I don't think we can call this
> "happen to" if there are 250+ of them?

Please, read through them. This "250+" number suddenly will become
like 20, because wrapper is not good enough.


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