Re: [Qemu-devel] [PATCH] crypto: afalg: fix a NULL pointer dereference

["Daniel P. Berrange" <berrange@redhat.com>]

On Tue, Nov 07, 2017 at 10:27:10AM +0800, Longpeng (Mike) wrote:
> 
> 
> On 2017/11/7 1:00, Eric Blake wrote:
> 
> > On 11/06/2017 12:21 AM, Longpeng(Mike) wrote:
> >> Test-crypto-hash calls qcrypto_hash_bytesv/digest/base64 with
> >> errp=NULL, this will cause a NULL poniter deference if afalg_driver
> > 
> > s/poniter deference/pointer dereference/
> > 
> 
> OK.
> 
> >> doesn't support requested algos:
> >>     ret = qcrypto_hash_afalg_driver.hash_bytesv(alg, iov, niov,
> >>                                                 result, resultlen,
> >>                                                 errp);
> >>     if (ret == 0) {
> >>         return ret;
> >>     }
> >>
> >>     error_free(*errp);  // <--- here
> >>
> >> So we must check 'errp & *errp' before dereference.
> > 
> > No, if we are going to blindly ignore the error from the hash_bytesv()
> > call, then we should pass NULL rather than errp.
> > 
> 
> The 'errp' in this palce is convenient for debug, it can tell us the reason for
> failure without stepping into afalg_driver's hash_bytesv().

It doesn't do anything useful for debug, because we are just immediately
throwing away the error without printing it anywhere. Just pass NULL into
the hash_bytesv call above.

Regards,
Daniel
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