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netfilter: nft_payload: do not update layer 4 checksum when mangling fragments

PATCH In review Florian Westphal 3 participants 5 messages Jan 28, 2022 – Jan 29, 2022

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Stable branch netfilter
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Florian Westphal

author maintainer
#0 lore raw

PATCH 1/1 netfilter: nft_payload: do not update layer 4 checksum when mangling fragments

From: Pablo Neira Ayuso <[email protected]>

commit 4e1860a3863707e8177329c006d10f9e37e097a8 upstream.

IP fragments do not come with the transport header, hence skip bogus layer 4 checksum updates.

Fixes 1814096980bb ("netfilter: nft_payload: layer 4 checksum adjustment for pseudoheader fields")
Reported-and-tested-by Steffen Weinreich <[email protected]>
Signed-off-by Pablo Neira Ayuso <[email protected]>
Signed-off-by Florian Westphal <[email protected]>

---
This is already in the 5.y branches but 4.19 needs a minor tweak as ->fragoff member resides in xt sub-struct.

 net/netfilter/nft_payload.c | 3 +++
 1 file changed, 3 insertions(+)
net/netfilter/nft_payload.c +3 -0
index b1a9f330a51f..fd87216bc0a9 100644
@@ -194,6 +194,9 @@ static int nft_payload_l4csum_offset(const struct nft_pktinfo *pkt,
 				     struct sk_buff *skb,
 				     unsigned int *l4csum_offset)
 {
+	if (pkt->xt.fragoff)
+		return -1;
+
 	switch (pkt->tprot) {
 	case IPPROTO_TCP:
 		*l4csum_offset = offsetof(struct tcphdr, check);
Signature · 1 line
2.34.1
maintainer
#1 lore raw
Quoted 7 lines · Florian Westphal

From: Pablo Neira Ayuso <[email protected]>

commit 4e1860a3863707e8177329c006d10f9e37e097a8 upstream.

IP fragments do not come with the transport header, hence skip bogus layer 4 checksum updates.

Quoted 7 lines
Fixes 1814096980bb ("netfilter: nft_payload: layer 4 checksum adjustment for pseudoheader fields")
Reported-and-tested-by Steffen Weinreich <[email protected]>
Signed-off-by Pablo Neira Ayuso <[email protected]>
Signed-off-by Florian Westphal <[email protected]>

---
This is already in the 5.y branches but 4.19 needs a minor tweak as ->fragoff member resides in xt sub-struct.

Thanks for taking care of this -stable submission.

Quoted 20 lines
 net/netfilter/nft_payload.c | 3 +++
 1 file changed, 3 insertions(+)
net/netfilter/nft_payload.c +3 -0
index b1a9f330a51f..fd87216bc0a9 100644
@@ -194,6 +194,9 @@ static int nft_payload_l4csum_offset(const struct nft_pktinfo *pkt,
 				     struct sk_buff *skb,
 				     unsigned int *l4csum_offset)
 {
+	if (pkt->xt.fragoff)
+		return -1;
+
 	switch (pkt->tprot) {
 	case IPPROTO_TCP:
 		*l4csum_offset = offsetof(struct tcphdr, check);
Signature · 1 line
2.34.1
maintainer
#2 lore raw
In reply to Florian Westphal
Quoted 7 lines · Florian Westphal

From: Pablo Neira Ayuso <[email protected]>

commit 4e1860a3863707e8177329c006d10f9e37e097a8 upstream.

IP fragments do not come with the transport header, hence skip bogus layer 4 checksum updates.

Quoted 7 lines
Fixes 1814096980bb ("netfilter: nft_payload: layer 4 checksum adjustment for pseudoheader fields")
Reported-and-tested-by Steffen Weinreich <[email protected]>
Signed-off-by Pablo Neira Ayuso <[email protected]>
Signed-off-by Florian Westphal <[email protected]>

---
This is already in the 5.y branches but 4.19 needs a minor tweak as ->fragoff member resides in xt sub-struct.

I don't see this commit in the 5.10 or 5.4 branches, am I missing something?

confused,

greg k-h

author maintainer
#3 lore raw
Quoted 16 lines · Greg KH
Quoted 7 lines · Florian Westphal

From: Pablo Neira Ayuso <[email protected]>

commit 4e1860a3863707e8177329c006d10f9e37e097a8 upstream.

IP fragments do not come with the transport header, hence skip bogus layer 4 checksum updates.

Quoted 7 lines
Fixes 1814096980bb ("netfilter: nft_payload: layer 4 checksum adjustment for pseudoheader fields")
Reported-and-tested-by Steffen Weinreich <[email protected]>
Signed-off-by Pablo Neira Ayuso <[email protected]>
Signed-off-by Florian Westphal <[email protected]>

---
This is already in the 5.y branches but 4.19 needs a minor tweak as ->fragoff member resides in xt sub-struct.

Quoted 2 lines

I don't see this commit in the 5.10 or 5.4 branches, am I missing something?

Oh, indeed. Can you place this patch in 5.4 and 5.10 too?

Releases >= v5.14 should be covered given upstream commit works as-is on those.

Thanks,
Florian

maintainer
#4 lore raw
Quoted 17 lines · Florian Westphal
Quoted 16 lines · Greg KH
Quoted 14 lines · Florian Westphal

From: Pablo Neira Ayuso <[email protected]>

commit 4e1860a3863707e8177329c006d10f9e37e097a8 upstream.

IP fragments do not come with the transport header, hence skip bogus layer 4 checksum updates.

Fixes 1814096980bb ("netfilter: nft_payload: layer 4 checksum adjustment for pseudoheader fields")
Reported-and-tested-by Steffen Weinreich <[email protected]>
Signed-off-by Pablo Neira Ayuso <[email protected]>
Signed-off-by Florian Westphal <[email protected]>

---
This is already in the 5.y branches but 4.19 needs a minor tweak as ->fragoff member resides in xt sub-struct.

Quoted 4 lines
Quoted 2 lines

I don't see this commit in the 5.10 or 5.4 branches, am I missing something?

Oh, indeed. Can you place this patch in 5.4 and 5.10 too?

Now done, and it was needed for 4.14.y, so I added it there too, thanks!

greg k-h