net: hsr: strict supervision TLV validation

From: Luka Gejak <[email protected]>

Changes in v6:
- Dropped capitalization comment changes per request of Jakub Kicinski

Changes in v5:
- Reverted TLV loop in Patch 1 to strict sequential parsing per IEC 62439-3.
- Retained pskb_may_pull() logic to ensure memory safety for TLV headers.
- Dropped Reviewed-by from Patch 1 due to the logic evolving since original review.
- Added Assisted-by tag for AI-aided translation and formatting to both patches.

Changes in v4:
- Split from a 4-patch series into 'net' and 'net-next' as requested.
- Implemented a TLV walker in Patch 1 to correctly handle extension TLVs and avoid regressions on paged frames/non-linearized skbs.
- Corrected pskb_may_pull() logic to include the TLV header size.

History of pre-separation series (v1-v3):
Changes in v3:
- addressed Felix review feedback in the VLAN add unwind fix
- removed the superfluous empty line

Changes in v2:
- picked up Reviewed-by tags on patches 1, 3 and 4
- changes in patch 2 per advice of Felix Maurer

Luka Gejak (2):
net: hsr: require valid EOT supervision TLV
net: hsr: reject unresolved interlink ifindex

 net/hsr/hsr_forward.c | 6 +++---
 net/hsr/hsr_netlink.c | 7 ++++++-
 2 files changed, 9 insertions(+), 4 deletions(-)

2.53.0

From: Luka Gejak <[email protected]>

Supervision frames are only valid if terminated with a zero-length EOT TLV. The current check fails to reject non-EOT entries as the terminal TLV, potentially allowing malformed supervision traffic.

Fix this by strictly requiring the terminal TLV to be HSR_TLV_EOT with a length of zero, and properly linearizing the TLV header before access.

---
 net/hsr/hsr_forward.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

index 0aca859c88cb..0774981a65c1 100644
@@ -84,7 +84,7 @@ static bool is_supervision_frame(struct hsr_priv *hsr, struct sk_buff *skb)
 
 	/* Get next tlv */
 	total_length += hsr_sup_tag->tlv.HSR_TLV_length;
-	if (!pskb_may_pull(skb, total_length))
+	if (!pskb_may_pull(skb, total_length + sizeof(struct hsr_sup_tlv)))
 		return false;
 	skb_pull(skb, total_length);
 	hsr_sup_tlv = (struct hsr_sup_tlv *)skb->data;

@@ -100,7 +100,7 @@ static bool is_supervision_frame(struct hsr_priv *hsr, struct sk_buff *skb)
 
 		/* make sure another tlv follows */
 		total_length += sizeof(struct hsr_sup_tlv) + hsr_sup_tlv->HSR_TLV_length;
-		if (!pskb_may_pull(skb, total_length))
+		if (!pskb_may_pull(skb, total_length + sizeof(struct hsr_sup_tlv)))
 			return false;
 
 		/* get next tlv */

@@ -110,7 +110,7 @@ static bool is_supervision_frame(struct hsr_priv *hsr, struct sk_buff *skb)
 	}
 
 	/* end of tlvs must follow at the end */
-	if (hsr_sup_tlv->HSR_TLV_type == HSR_TLV_EOT &&
+	if (hsr_sup_tlv->HSR_TLV_type != HSR_TLV_EOT ||
 	    hsr_sup_tlv->HSR_TLV_length != 0)
 		return false;
 

2.53.0

From: Luka Gejak <[email protected]>

In hsr_newlink(), a provided but invalid IFLA_HSR_INTERLINK attribute was silently ignored if __dev_get_by_index() returned NULL. This leads to incorrect RedBox topology creation without notifying the user.

Fix this by returning -EINVAL and an extack message when the interlink attribute is present but cannot be resolved.

---
 net/hsr/hsr_netlink.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

index db0b0af7a692..f0ca23da3ab9 100644
@@ -76,9 +76,14 @@ static int hsr_newlink(struct net_device *dev,
 		return -EINVAL;
 	}
 
-	if (data[IFLA_HSR_INTERLINK])
+	if (data[IFLA_HSR_INTERLINK]) {
 		interlink = __dev_get_by_index(link_net,
 					       nla_get_u32(data[IFLA_HSR_INTERLINK]));
+		if (!interlink) {
+			NL_SET_ERR_MSG_MOD(extack, "Interlink does not exist");
+			return -EINVAL;
+		}
+	}
 
 	if (interlink && interlink == link[0]) {
 		NL_SET_ERR_MSG_MOD(extack, "Interlink and Slave1 are the same");

2.53.0

Thanks!

...

Just one note: This series has been resubmitted because it was never merged due to window being closed and I was instructed by Felix to resubmit it now. Link to old thread is [1].
Best regards,
Luka Gejak
[1]: https://lore.kernel.org/netdev/[email protected]/