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

[Stefan Hajnoczi]

On Mon, Nov 06, 2017 at 02:21:11PM +0800, 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
> 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.

Only errp needs to be checked.  It's okay to invoke error_free(NULL):

  void error_free(Error *err)
  {
      if (err) {

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