[PATCH net-next v2 0/5] ynl/ethtool/netlink: fix nla_len overflow for large string sets

Hangbin Liu
2026-04-08T07:08:59Z

This series addresses a silent data corruption issue triggered when ynl
retrieves string sets from NICs with a large number of statistics entries
(e.g. mlx5_core with thousands of ETH_SS_STATS strings).

The root cause is that struct nlattr.nla_len is a __u16 (max 65535
bytes). When a NIC exports enough statistics strings, the
ETHTOOL_A_STRINGSET_STRINGS nest built by strset_fill_set() exceeds
this limit. nla_nest_end() silently truncates the length on assignment,
producing a corrupted netlink message.

Patch 1 moves ethtool.py to selftest.

Patch 2 improves the ethtool tool: rename the doit/dumpit helpers
to do_set/do_get and convert do_get to use ynl.do() with an
explicit device header instead of a full dump with client-side filtering.

Patch 3 adds a --dbg-small-recv option to the YNL ethtool tool,
matching the same option already present in cli.py, to help debug netlink
message size issues

Patch 4 adds a new helper nla_nest_end_safe() to check whether the nla_len
is overflow and return -EMSGSIZE early if so.

Patch 5 uses the new helper in ethtool to make sure the ethtool doesn't
reply a corrupted netlink message.

---
Changes in v2:
- move ethtool.py to selftest (Jakub Kicinski)
- add a new helper nla_nest_end_safe (Jakub Kicinski)
- Link to v1: https://lore.kernel.org/r/20260331-b4-ynl_ethtool-v1-0-dda2a9b55df8@gmail.com

---
Hangbin Liu (5):
tools: ynl: move ethtool.py to selftest
tools: ynl: ethtool: use doit instead of dumpit for per-device GET
tools: ynl: ethtool: add --dbg-small-recv option
netlink: add a nla_nest_end_safe() helper
ethtool: strset: check nla_len overflow

include/net/netlink.h | 19 ++++++++
net/ethtool/strset.c | 3 +-
tools/net/ynl/tests/Makefile | 5 +-
tools/net/ynl/{pyynl => tests}/ethtool.py | 79 ++++++++++++++++---------------
tools/net/ynl/tests/test_ynl_ethtool.sh | 2 +-
5 files changed, 68 insertions(+), 40 deletions(-)
---
base-commit: e65d8b6f3092398efd7c74e722cb7a516d9a0d6d
change-id: 20260324-b4-ynl_ethtool-f87cd42f572c

Best regards,
--
Hangbin Liu <liuhangbin@gmail.com>