Re: [edk2-devel] [PATCH v1 1/1] CryptoPkg: BaseCryptLib: Fix buffer double free in CryptPkcs7VerifyEku

["Laszlo Ersek" <lersek@redhat.com>]

On 10/21/20 04:32, Kun Qin wrote:
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2459
> 
> SignerCert is part of Pkcs7 instance when both have valid content. OpenSLL
> PKCS7_free function will release the memory of SignerCert when applicable.

Is this a security issue?

Thanks
Laszlo

> Freeing SignerCert with X509_free again might cause page fault if use-
> after-free guard is enabled.
> 
> Cc: Jian J Wang <jian.j.wang@intel.com>
> Cc: Xiaoyu Lu <xiaoyux.lu@intel.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Guomin Jiang <guomin.jiang@intel.com>
> 
> Signed-off-by: Kun Qin <kun.q@outlook.com>
> ---
>  CryptoPkg/Library/BaseCryptLib/Pk/CryptPkcs7VerifyEku.c | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/CryptoPkg/Library/BaseCryptLib/Pk/CryptPkcs7VerifyEku.c b/CryptoPkg/Library/BaseCryptLib/Pk/CryptPkcs7VerifyEku.c
> index c9fdb65b99d1..40cc39afe7dd 100644
> --- a/CryptoPkg/Library/BaseCryptLib/Pk/CryptPkcs7VerifyEku.c
> +++ b/CryptoPkg/Library/BaseCryptLib/Pk/CryptPkcs7VerifyEku.c
> @@ -508,10 +508,6 @@ Exit:
>      free (SignedData);
> 
>    }
> 
>  
> 
> -  if (SignerCert != NULL) {
> 
> -    X509_free (SignerCert);
> 
> -  }
> 
> -
> 
>    if (Pkcs7 != NULL) {
> 
>      PKCS7_free (Pkcs7);
> 
>    }
>