CVE-2026-68369: usb: gadget: printer: fix infinite loop in printer_read()

From: Greg Kroah-Hartman <[email protected]>

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

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

usb: gadget: printer: fix infinite loop in printer_read()

printer_read() uses the same variable for the requested copy size and
the number of bytes actually copied to user space. copy_to_user()
returns the number of bytes not copied, so when it fails to copy
anything, the computed copied length becomes zero.

In that case len, buf, current_rx_bytes and current_rx_buf are left
unchanged. If RX data is available and the user buffer remains
unwritable, the read loop can repeat indefinitely.

Track the copied length separately and return -EFAULT, or the number of
bytes already copied, if an iteration makes no progress.

The Linux kernel CVE team has assigned CVE-2026-68369 to this issue.


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

	Issue introduced in 4.1 with commit b185f01a9ab7af586133be2555298e960237359b and fixed in 6.6.148 with commit 994afccfdcceb73be33f69a8a8ea71e260c9eca5
	Issue introduced in 4.1 with commit b185f01a9ab7af586133be2555298e960237359b and fixed in 6.12.101 with commit e03597ad9494b500344076589aeaa6c6d2d381d3
	Issue introduced in 4.1 with commit b185f01a9ab7af586133be2555298e960237359b and fixed in 6.18.42 with commit 4cde0b38cc0cb8b7dc17295801015148de37d1d2
	Issue introduced in 4.1 with commit b185f01a9ab7af586133be2555298e960237359b and fixed in 7.1.6 with commit e41bbbbb1740ce4d7270ab1cdeca13892d6a8d2e
	Issue introduced in 4.1 with commit b185f01a9ab7af586133be2555298e960237359b and fixed in 7.2-rc5 with commit c2e819be6a5c7f34344926b4bd7e3dfca58cf48a

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-2026-68369
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/usb/gadget/function/f_printer.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/994afccfdcceb73be33f69a8a8ea71e260c9eca5
	https://git.kernel.org/stable/c/e03597ad9494b500344076589aeaa6c6d2d381d3
	https://git.kernel.org/stable/c/4cde0b38cc0cb8b7dc17295801015148de37d1d2
	https://git.kernel.org/stable/c/e41bbbbb1740ce4d7270ab1cdeca13892d6a8d2e
	https://git.kernel.org/stable/c/c2e819be6a5c7f34344926b4bd7e3dfca58cf48a