Re: [PATCH] dma-mapping: Add BUG_ON for uninitialized dma_ops

[Arnd Bergmann]

On Tuesday 11 June 2013, James Bottomley wrote:
> Really, no, it's not a good idea at all.  It invites tons of patches
> littering the code with BUG_ONs where we might possibly get a NULL
> dereference.  All it does is add extra instructions to a code path for
> no actual benefit.
> 
> If you can answer the question: what more information does the BUG_ON
> give you than the NULL deref Oops would not? then it might be
> reasonable.

The question is if a user can trigger the NULL dereference intentionally,
in which case they might get the kernel to jump into a  user-provided
buffer.

	Arnd
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