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

[Vladimir Sementsov-Ogievskiy]

07.03.2017 03:10, Philippe Mathieu-Daudé wrote:
> 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).

Agree.

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


--
Best regards,
Vladimir