CVE-2026-74384

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

nvme-multipath: fix flex array size in struct nvmenshead

struct nvmenshead contains a flexible array member, current_path[],

which is indexed using the NUMA node ID:

head->currentpath[numanode_id()]

The structure is currently allocated as:

size = sizeof(struct nvmenshead) +

       (numpossiblenodes()  sizeof(struct nvme_ns ));

head = kzalloc(size, GFP_KERNEL);

This allocation assumes that NUMA node IDs are sequential and densely

packed from 0 .. numpossiblenodes() - 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: numpossiblenodes() = 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 nvmempathrevalidatepaths+0x22c/0x290 [nvmecore]

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 asyncrunentry_fn

Call Trace:

[c000200037fa7510] [c0000000021c23d4] dumpstacklvl+0x88/0xdc (unreliable)

[c000200037fa7540] [c0000000009fda90] print_report+0x22c/0x67c

[c000200037fa7630] [c0000000009fd508] kasan_report+0x108/0x220

[c000200037fa7740] [c0000000009fff48] _asanstore8+0xe8/0x120

[c000200037fa7760] [c008000018e76474] nvmempathrevalidatepaths+0x22c/0x290 [nvmecore]

[c000200037fa7800] [c008000018e6556c] nvmeupdatensinfo+0x4a4/0x5e0 [nvmecore]

[c000200037fa7a50] [c008000018e66270] nvmeallocns+0x6d8/0x1a70 [nvme_core]

[c000200037fa7c20] [c008000018e679fc] nvmescanns+0x3f4/0x630 [nvme_core]

[c000200037fa7d10] [c00000000031f22c] asyncrunentry_fn+0x9c/0x3a0

[c000200037fa7db0] [c0000000002fa544] processonework+0x414/0xa10

[c000200037fa7ec0] [c0000000002fbf00] worker_thread+0x320/0x640

[c000200037fa7f80] [c00000000030d0f8] kthread+0x278/0x290

[c000200037fa7fe0] [c00000000000ded8] startkernelthread+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 nrnodeids instead

of numpossiblenodes(). Since nrnodeids represents the maximum

possible NUMA node IDs, indexing currentpath[] using numanode_id()

becomes safe even on systems with sparse node IDs.