Re: [Qemu-devel] [PATCH v3 2/3] crypto: avoid undefined behavior in nettle calls

[Daniel P. Berrange]

On Thu, Jul 16, 2015 at 06:04:00PM +0200, Radim Krčmář wrote:
> Calling a function pointer that was cast from an incompatible function
> results in undefined behavior.  'void *' isn't compatible with 'struct
> XXX *', so we can't cast to nettle_cipher_func, but have to provide a
> wrapper.  (Conversion from 'void *' to 'struct XXX *' might require
> computation, which won't be done if we drop argument's true type and
> pointers can have different sizes so passing arguments on stack would
> bug.)
> 
> Having two different prototypes based on nettle version doesn't make
> this solution any nicer.
> 
> Reported-by: Peter Maydell <address@hidden>
> Signed-off-by: Radim Krčmář <address@hidden>
> ---
>  v3: make wrappers 'static'
>  v2: new [Peter]
> 
>  crypto/cipher-nettle.c | 43 +++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 39 insertions(+), 4 deletions(-)

Reviewed-by: Daniel P. Berrange <address@hidden>

Regards,
Daniel
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