ipv6: ioam: fix heap buffer overflow in __ioam6_fill_trace_data()

Overview

In the Linux kernel, the following vulnerability has been resolved:

ipv6: ioam: fix heap buffer overflow in __ioam6_fill_trace_data()

On the receive path, __ioam6_fill_trace_data() uses trace->nodelen to decide how much data to write for each node. It trusts this field as-is from the incoming packet, with no consistency check against trace->type (the 24-bit field that tells which data items are present). A crafted packet can set nodelen=0 while setting type bits 0-21, causing the function to write ~100 bytes past the allocated region (into skb_shared_info), which corrupts adjacent heap memory and leads to a kernel panic.

Add a shared helper ioam6_trace_compute_nodelen() in ioam6.c to derive the expected nodelen from the type field, and use it:

• in ioam6_iptunnel.c (send path, existing validation) to replace the open-coded computation;
• in exthdrs.c (receive path, ipv6_hop_ioam) to drop packets whose nodelen is inconsistent with the type field, before any data is written.

Per RFC 9197, bits 12-21 are each short (4-octet) fields, so they are included in IOAM6_MASK_SHORT_FIELDS (changed from 0xff100000 to 0xff1ffc00).

Affected

• Linux >= 9ee11f0fff205b4b3df9750bff5e94f97c71b6a0 < f4d9d4b8fd839719d564651671e24c62c545c23b
• Linux >= 9ee11f0fff205b4b3df9750bff5e94f97c71b6a0 < fb3c662fafebc5b9d74417ed1de8759f6bb72143
• Linux >= 9ee11f0fff205b4b3df9750bff5e94f97c71b6a0 < 632d233cf2e64a46865ae2c064ae3c9df7c8864f
• Linux >= 9ee11f0fff205b4b3df9750bff5e94f97c71b6a0 < 0591d6509c2ff13f09ea2998434aba0c0472e978
• Linux >= 9ee11f0fff205b4b3df9750bff5e94f97c71b6a0 < e90346a2f1e8917d5760a44a1f61c44e3b36d96b
• Linux >= 9ee11f0fff205b4b3df9750bff5e94f97c71b6a0 < ea3632aefc04205436868541638e26f4a74d5637
• Linux >= 9ee11f0fff205b4b3df9750bff5e94f97c71b6a0 < 6db8b56eed62baacaf37486e83378a72635c04cc
• Linux 5.15

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.