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.
CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS Score: 9.8
AV:N - On IBM POWER cloud/enterprise hosts using NVMe-oF (TCP/RDMA/FC), a remote attacker on the storage fabric can deliver NVMe async namespace-changed completions that queue namespace rescans, driving nvme_scan_ns()→nvme_alloc_ns()→nvme_update_ns_info()→nvme_mpath_revalidate_paths() over the network-facing NVMe host transport.
AC:L - Once CONFIG_NVME_MULTIPATH is enabled on POWER systems with sparse NUMA IDs (e.g., nodes 0,8,252-255), indexing current_path[numa_node_id()] deterministically exceeds the num_possible_nodes()-sized allocation during boot scan, admin rescan, or multipath I/O without races or layout luck.
PR:N - Triggering the bug via remote NVMe async events or normal multipath block I/O requires no local account, CAP_SYS_ADMIN, or other host privileges; only an existing NVMe attachment (local PCIe or preconfigured fabric) on a vulnerable POWER NUMA topology.
UI:N - No victim user action is required beyond routine system operation such as boot-time namespace discovery, background kworker rescans, or ordinary storage I/O on multipathed NVMe namespaces.
S:U - The out-of-bounds slab write corrupts host kernel heap memory in the NVMe multipath driver, enabling kernel privilege escalation within the same security authority rather than crossing VM, container, or IOMMU boundaries.
C:H - KASAN reports an 8-byte slab-out-of-bounds write past the nvme_ns_head allocation; this heap corruption can overwrite adjacent kmalloc objects and be developed into arbitrary kernel memory disclosure primitives.
I:H - The unchecked current_path[] index allows attacker-influenced 8-byte pointer writes beyond the allocation boundary, providing a heap corruption primitive suitable for arbitrary kernel writes and potential code execution.
A:H - The confirmed slab-out-of-bounds write in nvme_mpath_revalidate_paths() can oops/panic the kernel during namespace scan or multipath I/O on affected POWER servers, causing complete node unavailability.
| Attack Vector |
Network |
Scope |
Unchanged |
| Attack Complexity |
Low |
Confidentiality Impact |
High |
| Privileges Required |
None |
Integrity Impact |
High |
| User Interaction |
None |
Availability Impact |
High |
AV:N - On IBM POWER cloud/enterprise hosts using NVMe-oF (TCP/RDMA/FC), a remote attacker on the storage fabric can deliver NVMe async namespace-changed completions that queue namespace rescans, driving nvme_scan_ns()→nvme_alloc_ns()→nvme_update_ns_info()→nvme_mpath_revalidate_paths() over the network-facing NVMe host transport.
AC:L - Once CONFIG_NVME_MULTIPATH is enabled on POWER systems with sparse NUMA IDs (e.g., nodes 0,8,252-255), indexing current_path[numa_node_id()] deterministically exceeds the num_possible_nodes()-sized allocation during boot scan, admin rescan, or multipath I/O without races or layout luck.
PR:N - Triggering the bug via remote NVMe async events or normal multipath block I/O requires no local account, CAP_SYS_ADMIN, or other host privileges; only an existing NVMe attachment (local PCIe or preconfigured fabric) on a vulnerable POWER NUMA topology.
UI:N - No victim user action is required beyond routine system operation such as boot-time namespace discovery, background kworker rescans, or ordinary storage I/O on multipathed NVMe namespaces.
S:U - The out-of-bounds slab write corrupts host kernel heap memory in the NVMe multipath driver, enabling kernel privilege escalation within the same security authority rather than crossing VM, container, or IOMMU boundaries.
C:H - KASAN reports an 8-byte slab-out-of-bounds write past the nvme_ns_head allocation; this heap corruption can overwrite adjacent kmalloc objects and be developed into arbitrary kernel memory disclosure primitives.
I:H - The unchecked current_path[] index allows attacker-influenced 8-byte pointer writes beyond the allocation boundary, providing a heap corruption primitive suitable for arbitrary kernel writes and potential code execution.
A:H - The confirmed slab-out-of-bounds write in nvme_mpath_revalidate_paths() can oops/panic the kernel during namespace scan or multipath I/O on affected POWER servers, causing complete node unavailability.
CVSS 3.1