Re: [Qemu-devel] [PATCH for-2.9] nbd/client: fix drop_sync [CVE-2017-2630]

[Philippe Mathieu-Daudé]

Hi Vladimir,

On 03/06/2017 07:30 PM, Eric Blake wrote:
> From: Vladimir Sementsov-Ogievskiy <address@hidden>
>
> Comparison symbol is misused. It may lead to memory corruption.
> Introduced in commit 7d3123e.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> Message-Id: <address@hidden>
> [eblake: add CVE details]
> Signed-off-by: Eric Blake <address@hidden>
> Reviewed-by: Marc-André Lureau <address@hidden>
> ---
>
> This one still hasn't been merged in; sending separately since the
> rest of my NBD series is now 2.10 material:
> https://lists.gnu.org/archive/html/qemu-devel/2017-02/msg04528.html
>
>  nbd/client.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/nbd/client.c b/nbd/client.c
> index 5c9dee3..165b33e 100644
> --- a/nbd/client.c
> +++ b/nbd/client.c
> @@ -94,7 +94,7 @@ static ssize_t drop_sync(QIOChannel *ioc, size_t size)
>      char small[1024];
>      char *buffer;
>
> -    buffer = sizeof(small) < size ? small : g_malloc(MIN(65536, size));
> +    buffer = sizeof(small) > size ? small : g_malloc(MIN(65536, size));

here ">=" seems correct/safe.
(if size is 1024, use small stack buffer too).

>      while (size > 0) {
>          ssize_t count = read_sync(ioc, buffer, MIN(65536, size));