CVE-2026-98831: of/overlay: don't leak fragment references when changeset init fails

CVE-2026-98831: of/overlay: don't leak fragment references when changeset init fails

[Greg Kroah-Hartman]

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

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

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

of/overlay: don't leak fragment references when changeset init fails

init_overlay_changeset() stores the number of initialized fragments
in ovcs->count only on full success. When find_target() or the
__symbols__ lookup fails partway through, the target and overlay
references taken for the fragments initialized so far are never
dropped: free_overlay_changeset() bounds its cleanup loop by
ovcs->count, which is still 0.

Store the running count on the error path so free_overlay_changeset()
puts whatever was set up. The store is guarded by ovcs->fragments
because on the allocation-failure path cnt still holds the counting
pass total while there is no fragments array; everywhere else cnt
only counts fully-initialized fragments.

The Linux kernel CVE team has assigned CVE-2026-98831 to this issue.


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

	Issue introduced in 4.15 with commit 61b4de4e0b384f4a22c55c3bada604da49cec4e1 and fixed in 6.12.113 with commit 894573e2fdaeb1b15030b7eebc22615edf28a6cd
	Issue introduced in 4.15 with commit 61b4de4e0b384f4a22c55c3bada604da49cec4e1 and fixed in 6.18.56 with commit 7a46f1917b320cc8762183b802301da02a191b6a
	Issue introduced in 4.15 with commit 61b4de4e0b384f4a22c55c3bada604da49cec4e1 and fixed in 7.2.10 with commit 3a23fb158ba517b77a2e5258263bdfdaa480f758
	Issue introduced in 4.15 with commit 61b4de4e0b384f4a22c55c3bada604da49cec4e1 and fixed in 7.3-rc6 with commit 1d62f0f2bc7edb12ed09f71203df0e47fa4efca4

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-2026-98831
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/of/overlay.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/894573e2fdaeb1b15030b7eebc22615edf28a6cd
	https://git.kernel.org/stable/c/7a46f1917b320cc8762183b802301da02a191b6a
	https://git.kernel.org/stable/c/3a23fb158ba517b77a2e5258263bdfdaa480f758
	https://git.kernel.org/stable/c/1d62f0f2bc7edb12ed09f71203df0e47fa4efca4