CVE-2026-98722: mtd: block2mtd: Fix divide error when erase_size is zero

CVE-2026-98722: mtd: block2mtd: Fix divide error when erase_size is zero

[Greg Kroah-Hartman]

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

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

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

mtd: block2mtd: Fix divide error when erase_size is zero

The erase size is parsed from the "block2mtd" module parameter and can
be set to zero. add_device() then evaluates

        if (size % erase_size)

with a zero divisor, which triggers a divide error:

divide error: 0000 [#1] PREEMPT SMP PTI
RIP: 0010:add_device drivers/mtd/devices/block2mtd.c:296 [inline]
RIP: 0010:block2mtd_setup2+0x592/0xda0 drivers/mtd/devices/block2mtd.c:459
Call Trace:
block2mtd_setup+0x27/0xe0 drivers/mtd/devices/block2mtd.c:476
param_attr_store+0x214/0x310 kernel/params.c:589
module_attr_store+0x65/0x90 kernel/params.c:904
kernfs_fop_write_iter+0x3a4/0x540 fs/kernfs/file.c:345
...

Reject a zero erase size before performing the modulo operation so the
existing "erasesize must be a divisor of device size" error path
reports the invalid argument and frees the device.

The Linux kernel CVE team has assigned CVE-2026-98722 to this issue.


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

	Issue introduced in 3.15 with commit ea6d833a3fddcd1d60414d48f34c7f4fbe88608f and fixed in 6.12.113 with commit 826170a49ca1315af6b293a02200585b1e2186d9
	Issue introduced in 3.15 with commit ea6d833a3fddcd1d60414d48f34c7f4fbe88608f and fixed in 6.18.56 with commit a991c28066e7ba4da7450bb04478849f7ac6a14a
	Issue introduced in 3.15 with commit ea6d833a3fddcd1d60414d48f34c7f4fbe88608f and fixed in 7.2.10 with commit 21d0f05989bf0d5cef57b467a7fa4feefbd7236a
	Issue introduced in 3.15 with commit ea6d833a3fddcd1d60414d48f34c7f4fbe88608f and fixed in 7.3-rc6 with commit b5965c4221165045e19736794ca5f48ae3d67142

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-2026-98722
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/devices/block2mtd.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/826170a49ca1315af6b293a02200585b1e2186d9
	https://git.kernel.org/stable/c/a991c28066e7ba4da7450bb04478849f7ac6a14a
	https://git.kernel.org/stable/c/21d0f05989bf0d5cef57b467a7fa4feefbd7236a
	https://git.kernel.org/stable/c/b5965c4221165045e19736794ca5f48ae3d67142