CVE-2025-68362: wifi: rtl818x: rtl8187: Fix potential buffer underflow in rtl8187_rx_cb()

CVE-2025-68362: wifi: rtl818x: rtl8187: Fix potential buffer underflow in rtl8187_rx_cb()

[Greg Kroah-Hartman]

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

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

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

wifi: rtl818x: rtl8187: Fix potential buffer underflow in rtl8187_rx_cb()

The rtl8187_rx_cb() calculates the rx descriptor header address
by subtracting its size from the skb tail pointer.
However, it does not validate if the received packet
(skb->len from urb->actual_length) is large enough to contain this
header.

If a truncated packet is received, this will lead to a buffer
underflow, reading memory before the start of the skb data area,
and causing a kernel panic.

Add length checks for both rtl8187 and rtl8187b descriptor headers
before attempting to access them, dropping the packet cleanly if the
check fails.

The Linux kernel CVE team has assigned CVE-2025-68362 to this issue.


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

	Issue introduced in 2.6.27 with commit 6f7853f3cbe457067e9fe05461f56c7ea4ac488c and fixed in 6.12.63 with commit 4758770a673c60d8f615809304d72e1432fa6355
	Issue introduced in 2.6.27 with commit 6f7853f3cbe457067e9fe05461f56c7ea4ac488c and fixed in 6.17.13 with commit 638d4148e166d114a4cd7becaae992ce1a815ed8
	Issue introduced in 2.6.27 with commit 6f7853f3cbe457067e9fe05461f56c7ea4ac488c and fixed in 6.18.2 with commit 5ebf0fe7eaef9f6173a4c6ea77c5353e21645d15
	Issue introduced in 2.6.27 with commit 6f7853f3cbe457067e9fe05461f56c7ea4ac488c and fixed in 6.19-rc1 with commit b647d2574e4583c2e3b0ab35568f60c88e910840

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-2025-68362
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/realtek/rtl818x/rtl8187/dev.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/4758770a673c60d8f615809304d72e1432fa6355
	https://git.kernel.org/stable/c/638d4148e166d114a4cd7becaae992ce1a815ed8
	https://git.kernel.org/stable/c/5ebf0fe7eaef9f6173a4c6ea77c5353e21645d15
	https://git.kernel.org/stable/c/b647d2574e4583c2e3b0ab35568f60c88e910840