CVE-2026-89602: erofs: skip sufficiently large global buffers when resizing

CVE-2026-89602: erofs: skip sufficiently large global buffers when resizing

[Greg Kroah-Hartman]

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

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

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

erofs: skip sufficiently large global buffers when resizing

z_erofs_gbuf_nrpages is advanced only after every global buffer has been
grown. If a resize fails after some buffers were enlarged, a retry
revisits those enlarged buffers.

Retrying the same size then returns -ENOMEM because alloc_pages_bulk()
has no pages to add and the unchanged return value is treated as a
failure. Retrying an intermediate size allocates a temporary pointer
array smaller than gbuf->nrpages and copies more existing pointers than
the array can hold.

Skip buffers that already satisfy the request. Once all remaining
buffers have caught up, advancing z_erofs_gbuf_nrpages again describes
the guaranteed minimum size across the pool.

The Linux kernel CVE team has assigned CVE-2026-89602 to this issue.


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

	Issue introduced in 6.10 with commit d6db47e571dcaecaeaafa8840d00ae849ae3907b and fixed in 6.18.51 with commit 7267557ce98ccd07faaf3bc86382448950cc4ff6
	Issue introduced in 6.10 with commit d6db47e571dcaecaeaafa8840d00ae849ae3907b and fixed in 7.2.4 with commit 7f4a89d4f0d6acaf4b756c31de48f2109a257b70
	Issue introduced in 6.10 with commit d6db47e571dcaecaeaafa8840d00ae849ae3907b and fixed in 7.3-rc1 with commit a7d097cf01301c5da37927c8f26123d006f0fd8a

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-2026-89602
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:
	fs/erofs/zutil.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/7267557ce98ccd07faaf3bc86382448950cc4ff6
	https://git.kernel.org/stable/c/7f4a89d4f0d6acaf4b756c31de48f2109a257b70
	https://git.kernel.org/stable/c/a7d097cf01301c5da37927c8f26123d006f0fd8a