CVE-2026-64318: partitions: aix: bound the pp_count scan to the ppe array

From: Greg Kroah-Hartman <[email protected]>

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

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

partitions: aix: bound the pp_count scan to the ppe array

aix_partition() reads the physical volume descriptor into a fixed-size
struct pvd and then scans its physical-partition-extent array:

	int numpps = be16_to_cpu(pvd->pp_count);
	...
	for (i = 0; i < numpps; i += 1) {
		struct ppe *p = pvd->ppe + i;
		...
		lp_ix = be16_to_cpu(p->lp_ix);

pvd points at a single kmalloc()'d struct pvd whose ppe[] member holds a
fixed ARRAY_SIZE(pvd->ppe) (1016) entries, but the loop runs up to the
on-disk pp_count.  pp_count is an unvalidated __be16 read straight from
the descriptor, so a crafted AIX image with pp_count larger than 1016
drives the loop to read pvd->ppe[i] past the end of the allocation (up
to 65535 entries, ~2 MB out of bounds).

The partition scan runs without mounting anything, when a block device
with a crafted AIX/IBM partition table appears (an attacker-supplied
image attached with losetup -P, or a device auto-scanned by udev), via
msdos_partition() -> aix_partition().

Clamp the scan to the number of entries the ppe[] array can hold.

The Linux kernel CVE team has assigned CVE-2026-64318 to this issue.


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

	Issue introduced in 3.11 with commit 6ceea22bbbc84fcf6bf0913bb3db8a657e9002f6 and fixed in 5.10.261 with commit 09861651617ba0fec089e8b9477439e68398c110
	Issue introduced in 3.11 with commit 6ceea22bbbc84fcf6bf0913bb3db8a657e9002f6 and fixed in 5.15.212 with commit 5eacdb1967378f5e5591cd27a2d8cdee2df1a599
	Issue introduced in 3.11 with commit 6ceea22bbbc84fcf6bf0913bb3db8a657e9002f6 and fixed in 6.1.178 with commit b5e9c09309e18fd9839ad007c238120353ca0cc4
	Issue introduced in 3.11 with commit 6ceea22bbbc84fcf6bf0913bb3db8a657e9002f6 and fixed in 6.6.145 with commit fd94a779020f2ecc8b2607f4c20b34acb1763b9a
	Issue introduced in 3.11 with commit 6ceea22bbbc84fcf6bf0913bb3db8a657e9002f6 and fixed in 6.12.96 with commit 4671bb74bba05fdd4acf670a35758c29e8c97b83
	Issue introduced in 3.11 with commit 6ceea22bbbc84fcf6bf0913bb3db8a657e9002f6 and fixed in 6.18.39 with commit ce93228e2193a17d2c58b656e439bb39fe5c3af8
	Issue introduced in 3.11 with commit 6ceea22bbbc84fcf6bf0913bb3db8a657e9002f6 and fixed in 7.1.4 with commit 44f37ee92fdcd377c41bdf6a31cdd8cc7d4c410e
	Issue introduced in 3.11 with commit 6ceea22bbbc84fcf6bf0913bb3db8a657e9002f6 and fixed in 7.2-rc1 with commit 2dc0bfd2fe355fb930de63c2f2eb8ced8570c579

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-2026-64318
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:
	block/partitions/aix.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/09861651617ba0fec089e8b9477439e68398c110
	https://git.kernel.org/stable/c/5eacdb1967378f5e5591cd27a2d8cdee2df1a599
	https://git.kernel.org/stable/c/b5e9c09309e18fd9839ad007c238120353ca0cc4
	https://git.kernel.org/stable/c/fd94a779020f2ecc8b2607f4c20b34acb1763b9a
	https://git.kernel.org/stable/c/4671bb74bba05fdd4acf670a35758c29e8c97b83
	https://git.kernel.org/stable/c/ce93228e2193a17d2c58b656e439bb39fe5c3af8
	https://git.kernel.org/stable/c/44f37ee92fdcd377c41bdf6a31cdd8cc7d4c410e
	https://git.kernel.org/stable/c/2dc0bfd2fe355fb930de63c2f2eb8ced8570c579