CVE-2026-74659net: bridge: mrp: fix uninitialised bytes on the wire

Official description

In the Linux kernel, the following vulnerability has been resolved: net: bridge: mrp: fix uninitialised bytes on the wire br_mrp_alloc_test_skb() builds MRP test frames on an skb from dev_alloc_skb(), which does not clear the linear data area. On the MRA ring-role branch the sub-option TLV header is appended with sub_tlv = skb_put(skb, sizeof(*sub_tlv)); sub_tlv->type = BR_MRP_SUB_TLV_HEADER_TEST_AUTO_MGR; so sub_tlv->length is never written, and the two trailing alignment bytes are appended with a bare skb_put() that does not clear them either. The neighbouring oui and sub_opt regions are explicitly zeroed, so three uninitialised bytes are left in every MRA MRP_Test frame that goes out. Put the sub-option TLV header and the alignment padding in a single skb_put_zero(), which clears both. The AUTO_MGR sub-TLV carries no payload, so the zeroed length field is already the value it should have.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/014c062d23c63ec77ef2cf17a0d9363c7441cc94
• https://git.kernel.org/stable/c/7ebc23ff03668042e0b0e4034bb1518d36198d9e
• https://git.kernel.org/stable/c/06d58b8d2f053ced82e01efaeb6e7c82891eed58
• https://git.kernel.org/stable/c/a5e385eeb2d6dbbbdebfa050e67c34734ae12693
• https://git.kernel.org/stable/c/5912cf1822fbe53ae275c147868740eb384a5d3e
• https://git.kernel.org/stable/c/e08665218040f8e312abe40f74543186f3c2c941
• https://git.kernel.org/stable/c/63488dba65ef91373ef616575b32eb0eb21459f4