CVE-2026-98827: wifi: ath9k_htc: bound TX aggregation to MAX_TX_BUF_SIZE

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

wifi: ath9k_htc: bound TX aggregation to MAX_TX_BUF_SIZE

__hif_usb_tx() dequeues up to MAX_TX_AGGR_NUM (20) frames into a
single tx_buf of MAX_TX_BUF_SIZE (32768) bytes, limiting the batch
by record count but never by cumulative byte length.

With large frames (MTU 2304), 20 aggregated frames of 2292 bytes
each exceed the allocation (20 * 2296 = 45920 bytes), so the
memcpy() in the loop writes up to 13152 bytes past tx_buf->buf
before usb_submit_urb().

Peek the queue head and stop before copying any record that would
cross MAX_TX_BUF_SIZE, then dispatch the current batch. Leftover
skbs remain queued and are drained on the next URB completion.

The byte bound changes the loop's exit semantics: it can now exit
before i == tx_skb_cnt - 1. Stock only finalized tx_buf->len on
that last index (len += offset), so an early break would submit a
URB holding only the last record's length while every dequeued skb
is freed on completion, silently dropping frames. Make tx_buf->len
a running total and advance tx_buf->offset per record instead; the
stride round_up(nskb->len + 4, 4) is identical to the stock stride
when the loop runs to completion.

Tested on hardware with an MTU 2304 flood: the loop stops at
record 15 (len = 32144, offset = 32144, within 32768), no
oversized URB is submitted, and MTU 1500 pings pass 20/20.

The Linux kernel CVE team has assigned CVE-2026-98827 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 2.6.35 with commit fb9987d0f748c983bb795a86f47522313f701a08 and fixed in 6.12.113 with commit c18882768a0fe253c70986c5fe66d9241570fbc4
	Issue introduced in 2.6.35 with commit fb9987d0f748c983bb795a86f47522313f701a08 and fixed in 6.18.56 with commit 345ce265cf604e84b5b560c21beaf4c6f269ab14
	Issue introduced in 2.6.35 with commit fb9987d0f748c983bb795a86f47522313f701a08 and fixed in 7.2.10 with commit e73a619f91b6cfec47bc1a94aea28df6849e5be3
	Issue introduced in 2.6.35 with commit fb9987d0f748c983bb795a86f47522313f701a08 and fixed in 7.3-rc6 with commit aeaca27c1db3106967ffbb2b517d98c835f6d500

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-2026-98827
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/ath/ath9k/hif_usb.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/c18882768a0fe253c70986c5fe66d9241570fbc4
	https://git.kernel.org/stable/c/345ce265cf604e84b5b560c21beaf4c6f269ab14
	https://git.kernel.org/stable/c/e73a619f91b6cfec47bc1a94aea28df6849e5be3
	https://git.kernel.org/stable/c/aeaca27c1db3106967ffbb2b517d98c835f6d500