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[173.184.25.106]) by smtp.gmail.com with ESMTPSA id 00721157ae682-8ae323ee0dcsm953887b3.17.2026.10.01.11.45.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 01 Oct 2026 11:45:37 -0700 (PDT) From: Chris Kelly To: linux-wireless@vger.kernel.org Cc: nbd@nbd.name, lorenzo@kernel.org, ryder.lee@mediatek.com, shayne.chen@mediatek.com, sean.wang@mediatek.com, deren.wu@mediatek.com, mingyen.hsieh@mediatek.com, lucid_duck@justthetip.ca, Chris Kelly , stable@vger.kernel.org Subject: [PATCH wireless] wifi: mt76: connac3: check headroom before pushing EHT radiotap TLVs Date: Thu, 1 Oct 2026 14:45:29 -0400 Message-ID: <20261001184529.502048-1-hoopyfrood42@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-wireless@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit mt76_connac3_mac_decode_eht_radiotap() pushes the EHT and U-SIG radiotap TLVs, 64 bytes, in front of the frame without checking that the skb has room for them. It may not: the rx skb is built over the buffer with nothing reserved -- mt76u_build_rx_skb() with MT_DRV_RX_DMA_HDR on USB, mt76_dma_rx_process() with a zero buf_offset on PCIe -- so the only headroom is the RX descriptor that mt7925_mac_fill_rx() pulls. A descriptor carrying the P-RXV (group 3) but no C-RXV (group 5) leaves 48 bytes: the EHT TLV takes all of them and the U-SIG push runs past skb->head. Seen once on an MT7925 USB adapter in monitor mode, hopping channels: skbuff: skb_under_panic: text:ffffffffc16f4a3c len:164 put:16 head:ffff8d4132ca3000 data:ffff8d4132ca2ff0 tail:0x94 end:0xec0 dev: kernel BUG at net/core/skbuff.c:214! RIP: 0010:skb_panic+0x59/0x5b Call Trace: skb_push.cold+0x14/0x14 mt76_connac3_mac_radiotap_push_tlv+0x1c/0x80 [mt76_connac_lib] mt76_connac3_mac_decode_eht_radiotap+0x7a/0x1d0 [mt76_connac_lib] mt7925_queue_rx_skb+0x686/0xde0 [mt7925_common] mt76u_process_rx_entry+0x2eb/0x330 [mt76_usb] mt76u_rx_worker+0xeb/0x2b0 [mt76_usb] Leave the EHT fields out of the radiotap header when there is no room for them; the frame is still delivered with the rest. Fixes: 97d7ab9f51ec ("wifi: mt76: mt7925: add EHT radiotap support in monitor mode") Cc: stable@vger.kernel.org Tested-by: Devin Wittmayer Assisted-by: Claude:claude-opus-5-5 Signed-off-by: Chris Kelly --- drivers/net/wireless/mediatek/mt76/mt76_connac3_mac.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/drivers/net/wireless/mediatek/mt76/mt76_connac3_mac.c b/drivers/net/wireless/mediatek/mt76/mt76_connac3_mac.c index 651fcd4..0ed8ee7 100644 --- a/drivers/net/wireless/mediatek/mt76/mt76_connac3_mac.c +++ b/drivers/net/wireless/mediatek/mt76/mt76_connac3_mac.c @@ -210,6 +210,17 @@ void mt76_connac3_mac_decode_eht_radiotap(struct sk_buff *skb, __le32 *rxv, "Should push tlv at the top of mac hdr")) return; + /* The TLVs are pushed in front of the frame, into its headroom. The + * skb is built over the rx buffer with nothing reserved, on USB and + * PCIe alike, so that headroom is only the RX descriptor just pulled: + * 48 bytes with the P-RXV and no C-RXV, less than the 64 the EHT and + * U-SIG TLVs take, and skb_push() past skb->head is a kernel BUG. + * Leave the EHT fields out then. + */ + if (skb_headroom(skb) < 2 * sizeof(struct ieee80211_radiotap_tlv) + + sizeof(*eht) + sizeof(u32) + sizeof(*usig)) + return; + eht = mt76_connac3_mac_radiotap_push_tlv(skb, IEEE80211_RADIOTAP_EHT, sizeof(*eht) + sizeof(u32)); usig = mt76_connac3_mac_radiotap_push_tlv(skb, IEEE80211_RADIOTAP_EHT_USIG, -- 2.55.0.windows.3