[PATCH AUTOSEL 6.18-5.10] wifi: mac80211_hwsim: reject undersized HWSIM_ATTR_TX_INFO

[Sasha Levin]

From: Ibrahim Hashimov <security@xxxxxxxxxxxx>

[ Upstream commit 3dc723ac78a6e4fa0fd49e27e487ed319da40a9f ]

hwsim_tx_info_frame_received_nl() casts the HWSIM_ATTR_TX_INFO payload
to a struct hwsim_tx_rate * and unconditionally reads
IEEE80211_TX_MAX_RATES entries (8 bytes) from it. The policy only bounds
the attribute from above (NLA_BINARY .len is a maximum) and the op sets
GENL_DONT_VALIDATE_STRICT, so a short or zero-length attribute is
accepted and the loop reads past the payload.

Require the exact length in the policy, so a malformed attribute is
rejected before the handler runs.

Signed-off-by: Ibrahim Hashimov <security@xxxxxxxxxxxx>
Assisted-by: AuditCode-AI:2026.07
Link: https://patch.msgid.link/20260721115346.17236-1-security@xxxxxxxxxxxx
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---

LLM Generated explanations, may be completely bogus:

The background history lookup didn’t finish — it was killed after ~67s
because it used `git log --all`, which is too slow on this repo.

That didn’t change the conclusion. The analysis already stands: this is
a small, maintainer-reviewed security fix (OOB read on undersized
`HWSIM_ATTR_TX_INFO`) in `mac80211_hwsim`, the buggy code is present in
this v6.18.44 tree, and a similar hwsim security fix was already
backported here.

**YES** for stable backport to this tree.

 drivers/net/wireless/virtual/mac80211_hwsim.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/virtual/mac80211_hwsim.c b/drivers/net/wireless/virtual/mac80211_hwsim.c
index a0724e1c53070..8294e2c344eb9 100644
--- a/drivers/net/wireless/virtual/mac80211_hwsim.c
+++ b/drivers/net/wireless/virtual/mac80211_hwsim.c
@@ -912,9 +912,9 @@ static const struct nla_policy hwsim_genl_policy[HWSIM_ATTR_MAX + 1] = {
 	[HWSIM_ATTR_FLAGS] = { .type = NLA_U32 },
 	[HWSIM_ATTR_RX_RATE] = { .type = NLA_U32 },
 	[HWSIM_ATTR_SIGNAL] = { .type = NLA_U32 },
-	[HWSIM_ATTR_TX_INFO] = { .type = NLA_BINARY,
-				 .len = IEEE80211_TX_MAX_RATES *
-					sizeof(struct hwsim_tx_rate)},
+	[HWSIM_ATTR_TX_INFO] =
+		NLA_POLICY_EXACT_LEN(IEEE80211_TX_MAX_RATES *
+				     sizeof(struct hwsim_tx_rate)),
 	[HWSIM_ATTR_COOKIE] = { .type = NLA_U64 },
 	[HWSIM_ATTR_CHANNELS] = { .type = NLA_U32 },
 	[HWSIM_ATTR_RADIO_ID] = { .type = NLA_U32 },
-- 
2.53.0