From: Zhengchao Shao shaozhengchao@huawei.com

hulk inclusion category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I5HWKR CVE: NA

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Syzbot found an issue [1]: fq_codel_drop() try to drop a flow whitout any skbs, that is, the flow->head is null. The root cause, as the [2] says, is because that bpf_prog_test_run_skb() run a bpf prog which redirects empty skbs. So we should determine whether the length of the packet modified by bpf prog or others like bpf_prog_test is valid before forwarding it directly.

LINK: [1] https://syzkaller.appspot.com/bug?id=0b84da80c2917757915afa89f7738a9d16ec96c... LINK: [2] https://www.spinics.net/lists/netdev/msg777503.html

Reported-by: syzbot+7a12909485b94426aceb@syzkaller.appspotmail.com Signed-off-by: Zhengchao Shao shaozhengchao@huawei.com Conflict: net/bpf/test_run.c Reviewed-by: Stanislav Fomichev sdf@google.com Link: https://lore.kernel.org/r/20220715115559.139691-1-shaozhengchao@huawei.com Signed-off-by: Alexei Starovoitov ast@kernel.org Reviewed-by: Wei Yongjun weiyongjun1@huawei.com Signed-off-by: Yongqiang Liu liuyongqiang13@huawei.com --- include/linux/skbuff.h | 8 ++++++++ net/bpf/test_run.c | 6 ++++++ net/core/dev.c | 1 + 3 files changed, 15 insertions(+)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index e9f100bd73d9..dbdb03ac557f 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -2077,6 +2077,14 @@ static inline void skb_set_tail_pointer(struct sk_buff *skb, const int offset)

#endif /* NET_SKBUFF_DATA_USES_OFFSET */

+static inline void skb_assert_len(struct sk_buff *skb) +{ +#ifdef CONFIG_DEBUG_NET + if (WARN_ONCE(!skb->len, "%s\n", __func__)) + DO_ONCE_LITE(skb_dump, KERN_ERR, skb, false); +#endif /* CONFIG_DEBUG_NET */ +} + /* * Add data to an sk_buff */ diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c index f4078830ea50..fba139c995aa 100644 --- a/net/bpf/test_run.c +++ b/net/bpf/test_run.c @@ -144,6 +144,12 @@ int bpf_prog_test_run_skb(struct bpf_prog *prog, const union bpf_attr *kattr, __skb_push(skb, hh_len); if (is_direct_pkt_access) bpf_compute_data_pointers(skb); + + if (!skb->len) { + kfree_skb(skb); + return -EINVAL; + } + retval = bpf_test_run(prog, skb, repeat, &duration); if (!is_l2) { if (skb_headroom(skb) < hh_len) { diff --git a/net/core/dev.c b/net/core/dev.c index 5bc0e56216c9..078e8a231616 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -3775,6 +3775,7 @@ static int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev) bool again = false;

skb_reset_mac_header(skb); + skb_assert_len(skb);

if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_SCHED_TSTAMP)) __skb_tstamp_tx(skb, NULL, skb->sk, SCM_TSTAMP_SCHED);