Re: [PATCH] net: ipv4: fix a memleak in ip_setup_cork

[Eric Dumazet]

On Fri, Jan 26, 2024 at 11:13 AM Eric Dumazet <edumazet@xxxxxxxxxx> wrote:
>
> On Fri, Jan 26, 2024 at 8:51 AM Zhipeng Lu <alexious@xxxxxxxxxx> wrote:
> >
> > When inetdev_valid_mtu fails, cork->opt should be freed if it is
> > allocated in ip_setup_cork. Otherwise there could be a memleak.
> >
> > Fixes: 501a90c94510 ("inet: protect against too small mtu values.")
> > Signed-off-by: Zhipeng Lu <alexious@xxxxxxxxxx>
> > ---
> >  net/ipv4/ip_output.c | 9 ++++++++-
> >  1 file changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
> > index b06f678b03a1..3215ea07d398 100644
> > --- a/net/ipv4/ip_output.c
> > +++ b/net/ipv4/ip_output.c
> > @@ -1282,6 +1282,7 @@ static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
> >  {
> >         struct ip_options_rcu *opt;
> >         struct rtable *rt;
> > +       int free_opt = 0;
> >
> >         rt = *rtp;
> >         if (unlikely(!rt))
> > @@ -1297,6 +1298,7 @@ static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
> >                                             sk->sk_allocation);
> >                         if (unlikely(!cork->opt))
> >                                 return -ENOBUFS;
> > +                       free_opt = 1;
> >                 }
> >                 memcpy(cork->opt, &opt->opt, sizeof(struct ip_options) + opt->opt.optlen);
> >                 cork->flags |= IPCORK_OPT;
> > @@ -1306,8 +1308,13 @@ static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
> >         cork->fragsize = ip_sk_use_pmtu(sk) ?
> >                          dst_mtu(&rt->dst) : READ_ONCE(rt->dst.dev->mtu);
> >
> > -       if (!inetdev_valid_mtu(cork->fragsize))
> > +       if (!inetdev_valid_mtu(cork->fragsize)) {
> > +               if (opt && free_opt) {
> > +                       kfree(cork->opt);
> > +                       cork->opt = NULL;
> > +               }
> >                 return -ENETUNREACH;
> > +       }
> >
> >         cork->gso_size = ipc->gso_size;
> >
> > --
> > 2.34.1
> >
>
> What about something simpler like :
>
> diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
> index b06f678b03a19b806fd14764a4caad60caf02919..41537d18eecfd6e1163aacc35e047c22468e04e6
> 100644
> --- a/net/ipv4/ip_output.c
> +++ b/net/ipv4/ip_output.c
> @@ -1287,6 +1287,12 @@ static int ip_setup_cork(struct sock *sk,
> struct inet_cork *cork,
>         if (unlikely(!rt))
>                 return -EFAULT;
>
> +       cork->fragsize = ip_sk_use_pmtu(sk) ?
> +                        dst_mtu(&rt->dst) : READ_ONCE(rt->dst.dev->mtu);
> +
> +       if (!inetdev_valid_mtu(cork->fragsize))
> +               return -ENETUNREACH;
> +
>         /*
>          * setup for corking.
>          */
> @@ -1303,12 +1309,6 @@ static int ip_setup_cork(struct sock *sk,
> struct inet_cork *cork,
>                 cork->addr = ipc->addr;
>         }
>
> -       cork->fragsize = ip_sk_use_pmtu(sk) ?
> -                        dst_mtu(&rt->dst) : READ_ONCE(rt->dst.dev->mtu);
> -
> -       if (!inetdev_valid_mtu(cork->fragsize))
> -               return -ENETUNREACH;
> -
>         cork->gso_size = ipc->gso_size;
>
>         cork->dst = &rt->dst;

Hi Zhipeng Lu

Could you send a V2 off your patch ? I will then add a Reviewed-by:
tag, thanks !