netdev - Re: [PATCH net] net/sched: act_ife: avoid possible NULL deref

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Message-ID: <CAM0EoMm-_afeMUQXeJsnTVcAhaj056m2WVzK85+=6XuVYJXXwg@mail.gmail.com>
Date: Wed, 21 Jan 2026 10:35:31 -0500
From: Jamal Hadi Salim <jhs@...atatu.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	Cong Wang <xiyou.wangcong@...il.com>, Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org, 
	eric.dumazet@...il.com, syzbot+5cf914f193dffde3bd3c@...kaller.appspotmail.com, 
	Yotam Gigi <yotam.gi@...il.com>
Subject: Re: [PATCH net] net/sched: act_ife: avoid possible NULL deref

On Wed, Jan 21, 2026 at 8:37 AM Eric Dumazet <edumazet@...gle.com> wrote:
>
> tcf_ife_encode() must make sure ife_encode() does not return NULL.
>
> syzbot reported:
>
> Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN NOPTI
> KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
>  RIP: 0010:ife_tlv_meta_encode+0x41/0xa0 net/ife/ife.c:166
> CPU: 3 UID: 0 PID: 8990 Comm: syz.0.696 Not tainted syzkaller #0 PREEMPT(full)
> Call Trace:
>  <TASK>
>   ife_encode_meta_u32+0x153/0x180 net/sched/act_ife.c:101
>   tcf_ife_encode net/sched/act_ife.c:841 [inline]
>   tcf_ife_act+0x1022/0x1de0 net/sched/act_ife.c:877
>   tc_act include/net/tc_wrapper.h:130 [inline]
>   tcf_action_exec+0x1c0/0xa20 net/sched/act_api.c:1152
>   tcf_exts_exec include/net/pkt_cls.h:349 [inline]
>   mall_classify+0x1a0/0x2a0 net/sched/cls_matchall.c:42
>   tc_classify include/net/tc_wrapper.h:197 [inline]
>   __tcf_classify net/sched/cls_api.c:1764 [inline]
>   tcf_classify+0x7f2/0x1380 net/sched/cls_api.c:1860
>   multiq_classify net/sched/sch_multiq.c:39 [inline]
>   multiq_enqueue+0xe0/0x510 net/sched/sch_multiq.c:66
>   dev_qdisc_enqueue+0x45/0x250 net/core/dev.c:4147
>   __dev_xmit_skb net/core/dev.c:4262 [inline]
>   __dev_queue_xmit+0x2998/0x46c0 net/core/dev.c:4798
>
> Fixes: 295a6e06d21e ("net/sched: act_ife: Change to use ife module")
> Reported-by: syzbot+5cf914f193dffde3bd3c@...kaller.appspotmail.com
> Closes: https://lore.kernel.org/netdev/6970d61d.050a0220.706b.0010.GAE@google.com/T/#u
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Yotam Gigi <yotam.gi@...il.com>
> ---
>  net/sched/act_ife.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/net/sched/act_ife.c b/net/sched/act_ife.c
> index 1dfdda6c2d4c51feb3f9db4e26e72c8e4a515687..8e8f6af731d51cd38cb469e4351a7c861fc6754b 100644
> --- a/net/sched/act_ife.c
> +++ b/net/sched/act_ife.c
> @@ -821,6 +821,7 @@ static int tcf_ife_encode(struct sk_buff *skb, const struct tc_action *a,
>         /* could be stupid policy setup or mtu config
>          * so lets be conservative.. */
>         if ((action == TC_ACT_SHOT) || exceed_mtu) {
> +drop:
>                 qstats_drop_inc(this_cpu_ptr(ife->common.cpu_qstats));
>                 return TC_ACT_SHOT;
>         }
> @@ -829,6 +830,8 @@ static int tcf_ife_encode(struct sk_buff *skb, const struct tc_action *a,
>                 skb_push(skb, skb->dev->hard_header_len);
>
>         ife_meta = ife_encode(skb, metalen);
> +       if (!ife_meta)
> +               goto drop;
>
>         spin_lock(&ife->tcf_lock);
>
> @@ -844,8 +847,7 @@ static int tcf_ife_encode(struct sk_buff *skb, const struct tc_action *a,
>                 if (err < 0) {
>                         /* too corrupt to keep around if overwritten */
>                         spin_unlock(&ife->tcf_lock);
> -                       qstats_drop_inc(this_cpu_ptr(ife->common.cpu_qstats));
> -                       return TC_ACT_SHOT;
> +                       goto drop;
>                 }
>                 skboff += err;
>         }

Reviewed-by: Jamal Hadi Salim <jhs@...atatu.com>

cheers,
jamal

> 2.52.0.457.g6b5491de43-goog
>