CVE-2026-74384: nvme-multipath: fix flex array size in struct nvme_ns_head

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

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

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

nvme-multipath: fix flex array size in struct nvme_ns_head

struct nvme_ns_head contains a flexible array member, current_path[],
which is indexed using the NUMA node ID:
head->current_path[numa_node_id()]

The structure is currently allocated as:
size = sizeof(struct nvme_ns_head) +
       (num_possible_nodes() * sizeof(struct nvme_ns *));
head = kzalloc(size, GFP_KERNEL);

This allocation assumes that NUMA node IDs are sequential and densely
packed from 0 .. num_possible_nodes() - 1. While this assumption holds
on many systems, it is not always true on some architectures such as
powerpc.

On some powerpc systems, NUMA node IDs can be sparse. For example:
NUMA:
  NUMA node(s):              6
  NUMA node0 CPU(s):         80-159
  NUMA node8 CPU(s):         0-79
  NUMA node252 CPU(s):
  NUMA node253 CPU(s):
  NUMA node254 CPU(s):
  NUMA node255 CPU(s):

That is, the possible/online NUMA node IDs are: 0, 8, 252, 253, 254, 255
In this case: num_possible_nodes() = 6

So memory is allocated for only 6 entries in current_path[]. However,
the array is later indexed using the actual NUMA node ID. As a result,
accesses such as:
head->current_path[8] or
head->current_path[252]
goes out of bounds, leading to the following KASAN splat:

==================================================================
BUG: KASAN: slab-out-of-bounds in nvme_mpath_revalidate_paths+0x22c/0x290 [nvme_core]
Write of size 8 at addr c00020003bda35b8 by task kworker/u641:2/1997

CPU: 1 UID: 0 PID: 1997 Comm: kworker/u641:2 Not tainted 7.1.0-rc5-dirty #14 PREEMPT(lazy)
Hardware name: 8335-GTH POWER9 0x4e1202 opal:skiboot-v6.5.3-35-g1851b2a06 PowerNV
Workqueue: async async_run_entry_fn
Call Trace:
[c000200037fa7510] [c0000000021c23d4] dump_stack_lvl+0x88/0xdc (unreliable)
[c000200037fa7540] [c0000000009fda90] print_report+0x22c/0x67c
[c000200037fa7630] [c0000000009fd508] kasan_report+0x108/0x220
[c000200037fa7740] [c0000000009fff48] __asan_store8+0xe8/0x120
[c000200037fa7760] [c008000018e76474] nvme_mpath_revalidate_paths+0x22c/0x290 [nvme_core]
[c000200037fa7800] [c008000018e6556c] nvme_update_ns_info+0x4a4/0x5e0 [nvme_core]
[c000200037fa7a50] [c008000018e66270] nvme_alloc_ns+0x6d8/0x1a70 [nvme_core]
[c000200037fa7c20] [c008000018e679fc] nvme_scan_ns+0x3f4/0x630 [nvme_core]
[c000200037fa7d10] [c00000000031f22c] async_run_entry_fn+0x9c/0x3a0
[c000200037fa7db0] [c0000000002fa544] process_one_work+0x414/0xa10
[c000200037fa7ec0] [c0000000002fbf00] worker_thread+0x320/0x640
[c000200037fa7f80] [c00000000030d0f8] kthread+0x278/0x290
[c000200037fa7fe0] [c00000000000ded8] start_kernel_thread+0x14/0x18

Allocated by task 1997 on cpu 1 at 35.928317s:

The buggy address belongs to the object at c00020003bda3000
 which belongs to the cache kmalloc-rnd-15-2k of size 2048
The buggy address is located 16 bytes to the right of
 allocated 1448-byte region [c00020003bda3000, c00020003bda35a8)

The buggy address belongs to the physical page:

Memory state around the buggy address:
 c00020003bda3480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 c00020003bda3500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>c00020003bda3580: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
                                        ^
 c00020003bda3600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 c00020003bda3680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Fix this by allocating the flexible array using nr_node_ids instead
of num_possible_nodes(). Since nr_node_ids represents the maximum
possible NUMA node IDs, indexing current_path[] using numa_node_id()
becomes safe even on systems with sparse node IDs.

The Linux kernel CVE team has assigned CVE-2026-74384 to this issue.


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

	Issue introduced in 4.20 with commit f333444708f82c4a4d3ccac004da0bfd9cfdfa42 and fixed in 5.10.261 with commit 7e7b167e65610dfa7564d449474f4b477f9d4c1c
	Issue introduced in 4.20 with commit f333444708f82c4a4d3ccac004da0bfd9cfdfa42 and fixed in 5.15.212 with commit 316b5f1168264844aa125959de1d6da2b1905795
	Issue introduced in 4.20 with commit f333444708f82c4a4d3ccac004da0bfd9cfdfa42 and fixed in 6.1.178 with commit 1d4131b5c9823c7d2c86389898ad1b466af7df5e
	Issue introduced in 4.20 with commit f333444708f82c4a4d3ccac004da0bfd9cfdfa42 and fixed in 6.6.145 with commit 9ffdd11bd6c961b46b3689850ff6c5d7af5c5fe5
	Issue introduced in 4.20 with commit f333444708f82c4a4d3ccac004da0bfd9cfdfa42 and fixed in 6.12.97 with commit bde4d6eb53f7d3cdae7e62c9ee84345fdd6e70a6
	Issue introduced in 4.20 with commit f333444708f82c4a4d3ccac004da0bfd9cfdfa42 and fixed in 6.18.40 with commit 140d6fff4ed266592492a23444043842b4af7a62
	Issue introduced in 4.20 with commit f333444708f82c4a4d3ccac004da0bfd9cfdfa42 and fixed in 7.1.5 with commit 7173a741fed73de6247384056fe92e582ba12507
	Issue introduced in 4.20 with commit f333444708f82c4a4d3ccac004da0bfd9cfdfa42 and fixed in 7.2-rc1 with commit 001e57554de81aa79c25c18fd53911d8a415c304

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-2026-74384
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/nvme/host/core.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/7e7b167e65610dfa7564d449474f4b477f9d4c1c
	https://git.kernel.org/stable/c/316b5f1168264844aa125959de1d6da2b1905795
	https://git.kernel.org/stable/c/1d4131b5c9823c7d2c86389898ad1b466af7df5e
	https://git.kernel.org/stable/c/9ffdd11bd6c961b46b3689850ff6c5d7af5c5fe5
	https://git.kernel.org/stable/c/bde4d6eb53f7d3cdae7e62c9ee84345fdd6e70a6
	https://git.kernel.org/stable/c/140d6fff4ed266592492a23444043842b4af7a62
	https://git.kernel.org/stable/c/7173a741fed73de6247384056fe92e582ba12507
	https://git.kernel.org/stable/c/001e57554de81aa79c25c18fd53911d8a415c304