Re: [Qemu-devel] [PATCH v1] ui: correctly advance output buffer when writing SASL data

[Laszlo Ersek]

On 02/01/18 16:58, Daniel P. Berrangé wrote:
> In this previous commit:
> 
>   commit 8f61f1c5a6bc06438a1172efa80bc7606594fa07
>   Author: Daniel P. Berrange <address@hidden>
>   Date:   Mon Dec 18 19:12:20 2017 +0000
> 
>     ui: track how much decoded data we consumed when doing SASL encoding
> 
> I attempted to fix a flaw with tracking how much data had actually been
> processed when encoding with SASL. With that flaw, the VNC server could
> mistakenly discard queued data that had not been sent.
> 
> The fix was not quite right though, because it merely decremented the
> vs->output.offset value. This is effectively to discarding data from the
> end of the pending output buffer. We actually need to discard data from
> the start of the pending output buffer. We also want to free memory that
> is no longer required. The correct way to handle this is to use the
> buffer_advance() helper method instead of directly manipulating the
> offset value.
> 
> Reported-by: Laszlo Ersek <address@hidden>
> Signed-off-by: Daniel P. Berrangé <address@hidden>
> ---
>  ui/vnc-auth-sasl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/ui/vnc-auth-sasl.c b/ui/vnc-auth-sasl.c
> index 74a5f513f2..fbccca8c8a 100644
> --- a/ui/vnc-auth-sasl.c
> +++ b/ui/vnc-auth-sasl.c
> @@ -84,7 +84,7 @@ size_t vnc_client_write_sasl(VncState *vs)
>          } else {
>              vs->force_update_offset -= vs->sasl.encodedRawLength;
>          }
> -        vs->output.offset -= vs->sasl.encodedRawLength;
> +        buffer_advance(&vs->output, vs->sasl.encodedRawLength);
>          vs->sasl.encoded = NULL;
>          vs->sasl.encodedOffset = vs->sasl.encodedLength = 0;
>      }
> 

With the typo pointed out by Eric fixed:

Reviewed-by: Laszlo Ersek <address@hidden>

Thank you!
Laszlo