[PATCH v2] wifi: libipw: reject TKIP frames without a full MIC

[Daehyeon Ko <4ncienth@gmail.com>]

libipw_michael_mic_verify() assumes that an skb contains an eight-byte
Michael MIC. A short TKIP frame makes the unsigned payload length wrap,
causing michael_mic() to read past the skb.

Check that the MIC is present before verifying it, and use the existing
MICHAEL_MIC_LEN constant for all MIC lengths in the verifier.

Fixes: b453872c35cf ("[NET] ieee80211 subsystem")
Cc: stable@vger.kernel.org
Assisted-by: LLM
Signed-off-by: Daehyeon Ko <4ncienth@gmail.com>
---
A tested source reproducer and full serial logs are available privately
to the maintainers on request. They are not included because this finding
was validated with AI assistance, as required by
Documentation/process/security-bugs.rst.

Changes in v2:
- Rewrite the commit message.
- Use the existing MICHAEL_MIC_LEN constant throughout the verifier.

Link: https://lore.kernel.org/r/20260908082729.209627-1-4ncienth@gmail.com

 .../net/wireless/intel/ipw2x00/libipw_crypto_tkip.c  | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/net/wireless/intel/ipw2x00/libipw_crypto_tkip.c b/drivers/net/wireless/intel/ipw2x00/libipw_crypto_tkip.c
index 24bb28ab7a49..2b0cf0ec496a 100644
--- a/drivers/net/wireless/intel/ipw2x00/libipw_crypto_tkip.c
+++ b/drivers/net/wireless/intel/ipw2x00/libipw_crypto_tkip.c
@@ -474,14 +474,16 @@ static int libipw_michael_mic_verify(struct sk_buff *skb, int keyidx,
 					int hdr_len, void *priv)
 {
 	struct libipw_tkip_data *tkey = priv;
-	u8 mic[8];
+	u8 mic[MICHAEL_MIC_LEN];
 
-	if (!tkey->key_set)
+	if (!tkey->key_set || skb->len < hdr_len + MICHAEL_MIC_LEN)
 		return -1;
 
 	michael_mic(&tkey->key[24], (struct ieee80211_hdr *)skb->data,
-		    skb->data + hdr_len, skb->len - 8 - hdr_len, mic);
-	if (memcmp(mic, skb->data + skb->len - 8, 8) != 0) {
+		    skb->data + hdr_len,
+		    skb->len - MICHAEL_MIC_LEN - hdr_len, mic);
+	if (memcmp(mic, skb->data + skb->len - MICHAEL_MIC_LEN,
+		   MICHAEL_MIC_LEN) != 0) {
 		struct ieee80211_hdr *hdr;
 		hdr = (struct ieee80211_hdr *)skb->data;
 		printk(KERN_DEBUG "%s: Michael MIC verification failed for "
@@ -499,7 +501,7 @@ static int libipw_michael_mic_verify(struct sk_buff *skb, int keyidx,
 	tkey->rx_iv32 = tkey->rx_iv32_new;
 	tkey->rx_iv16 = tkey->rx_iv16_new;
 
-	skb_trim(skb, skb->len - 8);
+	skb_trim(skb, skb->len - MICHAEL_MIC_LEN);
 
 	return 0;
 }

base-commit: a4d4c205cdb8657077f72bf0676b51df8ea8e01e
-- 
2.55.0