CVE-2026-89719: zram: fix out-of-bounds access in read_block_state()

CVE-2026-89719: zram: fix out-of-bounds access in read_block_state()

[Greg Kroah-Hartman]

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

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

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

zram: fix out-of-bounds access in read_block_state()

read_block_state() calculates nr_pages before taking dev_lock.  If the
device is reset and reinitialized with a smaller disksize before lock
acquisition, nr_pages still describes the old table.  The subsequent loop
can then call slot_lock() past the end of the newly allocated table.

Read disksize after acquiring dev_lock and checking that the device is
initialized.  The read lock then keeps the table and its bound stable for
the duration of the scan.

The Linux kernel CVE team has assigned CVE-2026-89719 to this issue.


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

	Issue introduced in 4.18 with commit c0265342bff4fcaa2cdf13f4596244c18d4a7ae5 and fixed in 6.18.51 with commit e7dbcb7a561a21e9a8f5b5fa90bb95aefbd0739d
	Issue introduced in 4.18 with commit c0265342bff4fcaa2cdf13f4596244c18d4a7ae5 and fixed in 7.2.4 with commit 5e458fa714a55b6b64a9fe0c6d4fa609609f9ec3
	Issue introduced in 4.18 with commit c0265342bff4fcaa2cdf13f4596244c18d4a7ae5 and fixed in 7.3-rc1 with commit 391f057f44a51cc9418da5cba78b014324174264

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-2026-89719
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/block/zram/zram_drv.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/e7dbcb7a561a21e9a8f5b5fa90bb95aefbd0739d
	https://git.kernel.org/stable/c/5e458fa714a55b6b64a9fe0c6d4fa609609f9ec3
	https://git.kernel.org/stable/c/391f057f44a51cc9418da5cba78b014324174264