linux-kernel - Re: [PATCH] Fixes the null pointer deferences in nsim

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Message-ID: <CANn89iL34Yiuas__P5WbtVM-mN5=ga-RhZV7Kdqo4a6KDxTv1g@mail.gmail.com>
Date:   Fri, 10 Nov 2023 09:52:59 +0100
From:   Eric Dumazet <edumazet@...gle.com>
To:     Dipendra Khadka <kdipendra88@...il.com>
Cc:     kuba@...nel.org, davem@...emloft.net, pabeni@...hat.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        syzbot+44c2416196b7c607f226@...kaller.appspotmail.com
Subject: Re: [PATCH] Fixes the null pointer deferences in nsim_bpf

On Fri, Nov 10, 2023 at 9:45 AM Dipendra Khadka <kdipendra88@...il.com> wrote:
>
> Syzkaller found a null pointer dereference in nsim_bpf
> originating from the lack of a null check for state.
>
> This patch fixes the issue by adding a check for state
> in two functions nsim_prog_set_loaded and nsim_setup_prog_hw_checks
>
> Reported-by: syzbot+44c2416196b7c607f226@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com./bug?extid=44c2416196b7c607f226

Please add a Fixes: tag, and remove this empty line, thanks.

>
> Signed-off-by: Dipendra Khadka <kdipendra88@...il.com>
> ---
>  drivers/net/netdevsim/bpf.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/net/netdevsim/bpf.c b/drivers/net/netdevsim/bpf.c
> index f60eb97e3a62..e407efb0e3de 100644
> --- a/drivers/net/netdevsim/bpf.c
> +++ b/drivers/net/netdevsim/bpf.c
> @@ -97,7 +97,8 @@ static void nsim_prog_set_loaded(struct bpf_prog *prog, bool loaded)
>                 return;
>
>         state = prog->aux->offload->dev_priv;
> -       state->is_loaded = loaded;
> +       if (state)
> +               state->is_loaded = loaded;
>  }
>
>  static int
> @@ -317,10 +318,12 @@ nsim_setup_prog_hw_checks(struct netdevsim *ns, struct netdev_bpf *bpf)
>         }
>
>         state = bpf->prog->aux->offload->dev_priv;
> -       if (WARN_ON(strcmp(state->state, "xlated"))) {
> -               NSIM_EA(bpf->extack, "offloading program in bad state");
> -               return -EINVAL;
> -       }
> +       if (state) {
> +               if (WARN_ON(strcmp(state->state, "xlated"))) {
> +                       NSIM_EA(bpf->extack, "offloading program in bad state");
> +                       return -EINVAL;
> +               }
> +       }
>         return 0;
>  }
>
> --
> 2.34.1
>