Re: [RFC][PATCH 1/1] support for user-space buffers in kfifo

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On 6/12/07, Stelian Pop <[email protected]> wrote:
Le lundi 11 juin 2007 à 16:26 -0500, Nelson Castillo a écrit :
> Hi.
>
> I just added support for user space buffers in kfifo. I found useful
> __kfifo_get_user to copy data to a user buffer in a read call. I didn't
> like the idea of having an extra buffer.
>
> * Is it ok to add this support?

I suppose it is, however:

> +     spin_lock_irqsave(fifo->lock, flags);
> +
> +     ret = __kfifo_put_user(fifo, buffer, len);
> +
> +     spin_unlock_irqrestore(fifo->lock, flags);
[...]

> +int __kfifo_put_user(struct kfifo *fifo, const unsigned char __user *buffer,
> +             unsigned int len)
[...]

> +     if(copy_from_user(fifo->buffer + (fifo->in & (fifo->size - 1)),
> +                       buffer, l))
> +             return  -EFAULT;
[...]

accessing userspace memory with a spinlock taken (moreover an irqsave()
one) is bad bad bad.

Yes.

Perhaps then only the functions __kfifo_put_user and __kfifo_get_user should
be allowed. Those are the ones I'm using now , anyway.
I added the others for completeness but adding them is probably a mistake.

Regards,
Nelson.-

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