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

Stelian.
--
Stelian Pop <stelian@popies.net>

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