CVE-2026-89552: params: fix charp corruption on allocation failure

CVE-2026-89552: params: fix charp corruption on allocation failure

[Greg Kroah-Hartman]

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

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

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

params: fix charp corruption on allocation failure

param_set_charp() stores charp parameters in allocated memory after slab is
available, and releases the previous value when the parameter is updated.

The previous value is released before the replacement allocation succeeds.
If kmalloc_parameter() fails, the setter returns -ENOMEM with the parameter
left as NULL.

Failing zswap's compressor update before zswap is initialized can later
trigger:

  BUG: kernel NULL pointer dereference, address: 0000000000000000
  RIP: 0010:strcmp+0x10/0x30
  Call Trace:
    zswap_setup+0x3b1/0x490
    zswap_enabled_param_set+0x5b/0xa0
    param_attr_store+0x93/0xe0
    module_attr_store+0x1c/0x30
    kernfs_fop_write_iter+0x116/0x1f0

Allocate and copy the replacement first, then replace the parameter value
only after allocation succeeds.

The Linux kernel CVE team has assigned CVE-2026-89552 to this issue.


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

	Issue introduced in 2.6.30 with commit e180a6b7759a99a28cbcce3547c4c80822cb6c2a and fixed in 6.12.109 with commit 614f873268c5b172804c9af6639bd17b7e1e2359
	Issue introduced in 2.6.30 with commit e180a6b7759a99a28cbcce3547c4c80822cb6c2a and fixed in 6.18.50 with commit 704ecd010d4a9b33160e40b74eb402f6b86a18e0
	Issue introduced in 2.6.30 with commit e180a6b7759a99a28cbcce3547c4c80822cb6c2a and fixed in 7.2.4 with commit 0d8e2404925a0607ffec79a53170715a46936896
	Issue introduced in 2.6.30 with commit e180a6b7759a99a28cbcce3547c4c80822cb6c2a and fixed in 7.3-rc1 with commit 3dfaae04243cde460d82dfc2a7dd0bb6664d20ae

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-2026-89552
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:
	kernel/params.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/614f873268c5b172804c9af6639bd17b7e1e2359
	https://git.kernel.org/stable/c/704ecd010d4a9b33160e40b74eb402f6b86a18e0
	https://git.kernel.org/stable/c/0d8e2404925a0607ffec79a53170715a46936896
	https://git.kernel.org/stable/c/3dfaae04243cde460d82dfc2a7dd0bb6664d20ae