[PATCH 5.4 140/658] bpf: Move skb->len == 0 checks into __bpf_redirect

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From: Stanislav Fomichev <sdf@xxxxxxxxxx>

[ Upstream commit 114039b342014680911c35bd6b72624180fd669a ]

To avoid potentially breaking existing users.

Both mac/no-mac cases have to be amended; mac_header >= network_header
is not enough (verified with a new test, see next patch).

Fixes: fd1894224407 ("bpf: Don't redirect packets with invalid pkt_len")
Signed-off-by: Stanislav Fomichev <sdf@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20221121180340.1983627-1-sdf@xxxxxxxxxx
Signed-off-by: Martin KaFai Lau <martin.lau@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 net/bpf/test_run.c | 3 ---
 net/core/filter.c  | 7 ++++++-
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index d78c4cc30a28..591d146a5308 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -201,9 +201,6 @@ 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/filter.c b/net/core/filter.c
index e81f7772161a..6fd9173e18b7 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2071,6 +2071,11 @@ static int __bpf_redirect_no_mac(struct sk_buff *skb, struct net_device *dev,
 {
 	unsigned int mlen = skb_network_offset(skb);
 
+	if (unlikely(skb->len <= mlen)) {
+		kfree_skb(skb);
+		return -ERANGE;
+	}
+
 	if (mlen) {
 		__skb_pull(skb, mlen);
 
@@ -2092,7 +2097,7 @@ static int __bpf_redirect_common(struct sk_buff *skb, struct net_device *dev,
 				 u32 flags)
 {
 	/* Verify that a link layer header is carried */
-	if (unlikely(skb->mac_header >= skb->network_header)) {
+	if (unlikely(skb->mac_header >= skb->network_header || skb->len == 0)) {
 		kfree_skb(skb);
 		return -ERANGE;
 	}
-- 
2.35.1






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