[ovs-dev] [PATCH] netdev-linux: Fix a null pointer dereference in netdev_linux_notify_sock()

Flavio Leitner fbl at redhat.com
Thu Sep 9 14:24:30 UTC 2021


On Thu, Sep 09, 2021 at 02:08:50PM +0200, David Marchand wrote:
> On Wed, Sep 8, 2021 at 1:53 PM Yunjian Wang <wangyunjian at huawei.com> wrote:
> >
> > If nl_sock_join_mcgroup() returns an error, the 'sock' is freed
> > and set to NULL. So we should add NULL check of 'sock' before calling
> > nl_sock_listen_all_nsid().
> >
> > Fixes: cf114a7fce80 ("netlink linux: enable listening to all nsids")
> > Cc: Flavio Leitner <fbl at redhat.com>
> > Signed-off-by: Yunjian Wang <wangyunjian at huawei.com>
> > ---
> >  lib/netdev-linux.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/lib/netdev-linux.c b/lib/netdev-linux.c
> > index 60dd13891..7fec5f5a6 100644
> > --- a/lib/netdev-linux.c
> > +++ b/lib/netdev-linux.c
> > @@ -636,7 +636,9 @@ netdev_linux_notify_sock(void)
> >                  }
> >              }
> >          }
> > -        nl_sock_listen_all_nsid(sock, true);
> > +        if (sock) {
> > +            nl_sock_listen_all_nsid(sock, true);
> > +        }
> >          ovsthread_once_done(&once);
> >      }
> >
> 
> Would it make sense to move this call before the loop on groups?
> Something like:

It does to me. The nl_sock_listen_all_nsid() only sets a flag in
the socket, so it should not matter whether it is done before or
after joining the mcgroups.

fbl


> 
> @@ -627,6 +627,7 @@ netdev_linux_notify_sock(void)
>          if (!error) {
>              size_t i;
> 
> +            nl_sock_listen_all_nsid(sock, true);
>              for (i = 0; i < ARRAY_SIZE(mcgroups); i++) {
>                  error = nl_sock_join_mcgroup(sock, mcgroups[i]);
>                  if (error) {
> @@ -636,7 +637,6 @@ netdev_linux_notify_sock(void)
>                  }
>              }
>          }
> -        nl_sock_listen_all_nsid(sock, true);
>          ovsthread_once_done(&once);
>      }
> 
> 
> -- 
> David Marchand
> 

-- 
fbl



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