Re: [Qemu-devel] [PATCH] cipher: fix leak on initialization error

[Marc-André Lureau]

Hi

----- Original Message -----
> On Wed, Nov 09, 2016 at 02:18:15PM +0400, Marc-André Lureau wrote:
> > If ctx->blocksize != XTS_BLOCK_SIZE, ctx will be leaked.
> > Assign ctx earler, and call qcrypto_cipher_free() on error.
> > 
> > Spotted thanks to ASAN.
> > 
> > Signed-off-by: Marc-André Lureau <address@hidden>
> > ---
> >  crypto/cipher-nettle.c | 15 ++++++++-------
> >  1 file changed, 8 insertions(+), 7 deletions(-)
> > 
> > diff --git a/crypto/cipher-nettle.c b/crypto/cipher-nettle.c
> > index cd094cd..593962c 100644
> > --- a/crypto/cipher-nettle.c
> > +++ b/crypto/cipher-nettle.c
> > @@ -376,6 +376,7 @@ QCryptoCipher
> > *qcrypto_cipher_new(QCryptoCipherAlgorithm alg,
> >          goto error;
> >      }
> 
> 'ctx' is non-NULL at this point and there's a 'goto error' just
> above here....
> 

Right, fixing it sending v2

> >  
> > +    cipher->opaque = ctx;
> >      if (mode == QCRYPTO_CIPHER_MODE_XTS &&
> >          ctx->blocksize != XTS_BLOCK_SIZE) {
> >          error_setg(errp, "Cipher block size %zu must equal XTS block size
> >          %d",
> > @@ -384,13 +385,11 @@ QCryptoCipher
> > *qcrypto_cipher_new(QCryptoCipherAlgorithm alg,
> >      }
> >  
> >      ctx->iv = g_new0(uint8_t, ctx->blocksize);
> > -    cipher->opaque = ctx;
> >  
> >      return cipher;
> >  
> >   error:
> > -    g_free(cipher);
> > -    g_free(ctx);
> > +    qcrypto_cipher_free(cipher);
> >      return NULL;
> >  }
> 
> 
> ...so you're leaking 'ctx' now, since it hasn't been assigned
> to cipher->ctx.
> 
> You need to move 'cipher->opque = ctx' to the place where we
> initially allocate 'ctx', before any gotos at which point....
> 
> >  
> > @@ -404,10 +403,12 @@ void qcrypto_cipher_free(QCryptoCipher *cipher)
> >      }
> >  
> >      ctx = cipher->opaque;
> > -    g_free(ctx->iv);
> > -    g_free(ctx->ctx);
> > -    g_free(ctx->ctx_tweak);
> > -    g_free(ctx);
> > +    if (ctx) {
> > +        g_free(ctx->iv);
> > +        g_free(ctx->ctx);
> > +        g_free(ctx->ctx_tweak);
> > +        g_free(ctx);
> > +    }
> >      g_free(cipher);
> >  }
> 
> ...this change is not needed
> 
> Regards,
> Daniel
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