[PATCH AUTOSEL 5.18 69/93] bpf: Don't redirect packets with invalid pkt_len
From: Sasha Levin <sashal@kernel.org>
Date: 2022-08-11 16:08:26
Also in:
bpf, lkml, stable
Subsystem:
bpf [general] (safe dynamic programs and tools), networking [general], the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
From: Zhengchao Shao <redacted> [ Upstream commit fd1894224407c484f652ad456e1ce423e89bb3eb ] 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=0b84da80c2917757915afa89f7738a9d16ec96c5 LINK: [2] https://www.spinics.net/lists/netdev/msg777503.html Reported-by: syzbot+7a12909485b94426aceb@syzkaller.appspotmail.com Signed-off-by: Zhengchao Shao <redacted> Reviewed-by: Stanislav Fomichev <redacted> Link: https://lore.kernel.org/r/20220715115559.139691-1-shaozhengchao@huawei.com (local) Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> --- include/linux/skbuff.h | 8 ++++++++ net/bpf/test_run.c | 3 +++ net/core/dev.c | 1 + 3 files changed, 12 insertions(+)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 2394441fa3dd..4fac0091fb65 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h@@ -2475,6 +2475,14 @@ 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 af709c182674..f2a9c47c26fc 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c@@ -911,6 +911,9 @@ static int convert___skb_to_skb(struct sk_buff *skb, struct __sk_buff *__skb) { struct qdisc_skb_cb *cb = (struct qdisc_skb_cb *)skb->cb; + if (!skb->len) + return -EINVAL; + if (!__skb) return 0;
diff --git a/net/core/dev.c b/net/core/dev.c
index 842917883adb..301fa691b265 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c@@ -4102,6 +4102,7 @@ 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, NULL, skb->sk, SCM_TSTAMP_SCHED);
--
2.35.1