From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-cve-announce@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@kernel.org>
Subject: CVE-2026-80825: wifi: mt76: mt7925: ensure tx headroom in usb_sdio_tx_prepare_skb
Date: Fri, 4 Sep 2026 17:52:52 +0200 [thread overview]
Message-ID: <2026090454-CVE-2026-80825-3632@gregkh> (raw)
From: Greg Kroah-Hartman <gregkh@kernel.org>
Description
===========
In the Linux kernel, the following vulnerability has been resolved:
wifi: mt76: mt7925: ensure tx headroom in usb_sdio_tx_prepare_skb
mt7925_usb_sdio_tx_prepare_skb() pushes a TX descriptor and a USB
header onto every skb and assumes the headroom for them is already
there. That holds for locally generated traffic, where mac80211
reserves hw->extra_tx_headroom, but forwarded frames are sent through
ieee80211_8023_xmit(), which does not reserve it. Bridge a wired
interface to an mt7925u AP and the first forwarded frame that arrives
short panics the kernel:
skbuff: skb_under_panic: len:415 put:4 tail:0x19b end:0x640 dev:wlan1
kernel BUG at net/core/skbuff.c:212!
Call trace:
skb_panic+0x58/0x60 (P)
skb_push+0x58/0x60
mt7925_usb_sdio_tx_prepare_skb+0xf8/0x1b8 [mt7925_common]
mt76u_tx_queue_skb+0xa0/0x1f8 [mt76_usb]
__mt76_tx_queue_skb+0x54/0xe8 [mt76]
mt76_txq_schedule.part.0+0x204/0x478 [mt76]
mt76_txq_schedule_all+0x50/0x80 [mt76]
mt792x_tx_worker+0x68/0x100 [mt792x_lib]
__mt76_worker_fn+0x84/0x150 [mt76]
Whether a given setup hits it depends on how much headroom the ingress
netdev leaves in its rx skbs. Reproduced on a Raspberry Pi 5 bridging
onboard ethernet to a Netgear A9000; originally reported on an MT7986
router running OpenWrt. Nick Morrow's testing on a Pi 4 (bcmgenet),
which leaves more headroom, helped narrow the trigger to the ingress
path.
The same bug was fixed on mt7921 by commit 98c4d0abf5c4 ("mt76:
mt7921: don't assume adequate headroom for SDIO headers"), but mt7925
was copied from mt7921 without the fix. Add the same guard here.
The Linux kernel CVE team has assigned CVE-2026-80825 to this issue.
Affected and fixed versions
===========================
Issue introduced in 6.7 with commit c948b5da6bbec742b433138e3e3f9537a85af2e5 and fixed in 6.12.108 with commit 9a72b180f0575e41471e088e09bddc4b73d6dee2
Issue introduced in 6.7 with commit c948b5da6bbec742b433138e3e3f9537a85af2e5 and fixed in 6.18.49 with commit 22edb6786127271aeba7abd30f152977c605c6a3
Issue introduced in 6.7 with commit c948b5da6bbec742b433138e3e3f9537a85af2e5 and fixed in 7.1.13 with commit 8d481f93588932a95f657671d4e1601b90d130cc
Issue introduced in 6.7 with commit c948b5da6bbec742b433138e3e3f9537a85af2e5 and fixed in 7.2.3 with commit e5e8fc11a7ac578f16079f855b7fffc1649d053c
Issue introduced in 6.7 with commit c948b5da6bbec742b433138e3e3f9537a85af2e5 and fixed in 7.3-rc1 with commit ef3e34874d2332d0f63e72c2c35ce5c93568c125
Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.
Unaffected versions might change over time as fixes are backported to
older supported kernel versions. The official CVE entry at
https://cve.org/CVERecord/?id=CVE-2026-80825
will be updated if fixes are backported, please check that for the most
up to date information about this issue.
Affected files
==============
The file(s) affected by this issue are:
drivers/net/wireless/mediatek/mt76/mt7925/mac.c
Mitigation
==========
The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes. Individual
changes are never tested alone, but rather are part of a larger kernel
release. Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all. If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
https://git.kernel.org/stable/c/9a72b180f0575e41471e088e09bddc4b73d6dee2
https://git.kernel.org/stable/c/22edb6786127271aeba7abd30f152977c605c6a3
https://git.kernel.org/stable/c/8d481f93588932a95f657671d4e1601b90d130cc
https://git.kernel.org/stable/c/e5e8fc11a7ac578f16079f855b7fffc1649d053c
https://git.kernel.org/stable/c/ef3e34874d2332d0f63e72c2c35ce5c93568c125
reply other threads:[~2026-09-04 15:55 UTC|newest]
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