CVE-2026-72155: mtd: spi-nor: swp: Improve locking user experience

CVE-2026-72155: mtd: spi-nor: swp: Improve locking user experience

[Greg Kroah-Hartman]

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

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

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

mtd: spi-nor: swp: Improve locking user experience

In the case of the first block being locked (or the few first blocks),
if the user want to fully unlock the device it has two possibilities:
- either it asks to unlock the entire device, and this works;
- or it asks to unlock just the block(s) that are currently locked,
  which fails.

It fails because the conditions "can_be_top" and "can_be_bottom" are
true. Indeed, in this case, we unlock everything, so the TB bit does not
matter. However in the current implementation, use_top would be true (as
this is the favourite option) and lock_len, which in practice should be
reduced down to 0, is set to "nor->params->size - (ofs + len)" which is
a positive number. This is wrong.

An easy way is to simply add an extra condition. In the unlock() path,
if we can achieve the same result from both sides, it means we unlock
everything and lock_len must simply be 0. A comment is added to clarify
that logic.

The Linux kernel CVE team has assigned CVE-2026-72155 to this issue.


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

	Issue introduced in 4.6 with commit 3dd8012a8eeb3702fa17450ec1a16a3f38af138d and fixed in 6.1.178 with commit 9a0d8dec3d11ca95d67537ea8fa6ee2730a5038a
	Issue introduced in 4.6 with commit 3dd8012a8eeb3702fa17450ec1a16a3f38af138d and fixed in 6.6.145 with commit dc341272cf8e15a2c511db3c4df5dab8adf70ad0
	Issue introduced in 4.6 with commit 3dd8012a8eeb3702fa17450ec1a16a3f38af138d and fixed in 6.12.97 with commit 6110ab5ffd84e8daa654652446a03ce2f77580a7
	Issue introduced in 4.6 with commit 3dd8012a8eeb3702fa17450ec1a16a3f38af138d and fixed in 6.18.40 with commit c0806df5cf806545160f3fdac3c888926ceac557
	Issue introduced in 4.6 with commit 3dd8012a8eeb3702fa17450ec1a16a3f38af138d and fixed in 7.1.5 with commit 12d4d69221159e6d0e72400ec81195d691169b53
	Issue introduced in 4.6 with commit 3dd8012a8eeb3702fa17450ec1a16a3f38af138d and fixed in 7.2-rc1 with commit e1d456b26bf23e30db305a6184e8abd9ab68bbf2

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-2026-72155
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/mtd/spi-nor/swp.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/9a0d8dec3d11ca95d67537ea8fa6ee2730a5038a
	https://git.kernel.org/stable/c/dc341272cf8e15a2c511db3c4df5dab8adf70ad0
	https://git.kernel.org/stable/c/6110ab5ffd84e8daa654652446a03ce2f77580a7
	https://git.kernel.org/stable/c/c0806df5cf806545160f3fdac3c888926ceac557
	https://git.kernel.org/stable/c/12d4d69221159e6d0e72400ec81195d691169b53
	https://git.kernel.org/stable/c/e1d456b26bf23e30db305a6184e8abd9ab68bbf2