In the Linux kernel, the following vulnerability has been resolved:
mm/hugetlb_cma: fix null nodemask dereference in hugetlb_cma_alloc_frozen_folio
alloc_buddy_hugetlb_folio_with_mpol() can pass a NULL nodemask to
alloc_fresh_hugetlb_folio() as a fallback to allocate from all nodes. If
order is gigantic, alloc_fresh_hugetlb_folio() propagates the NULL
nodemask down to hugetlb_cma_alloc_frozen_folio() via
alloc_gigantic_frozen_folio().
Additionally, hugetlb_cma_alloc_frozen_folio() previously attempted
allocation on hugetlb_cma[nid] without verifying if nid is included in the
caller's nodemask. Adding a node_isset(nid, *nodemask) check ensures the
initial preferred node allocation honors the memory policy / nodemask.
However, hugetlb_cma_alloc_frozen_folio() dereferences the nodemask in
node_isset(nid, *nodemask) and for_each_node_mask(node, *nodemask),
leading to a null pointer dereference kernel panic when nodemask is NULL.
Fix this by checking if nodemask is NULL in
hugetlb_cma_alloc_frozen_folio() and defaulting it to
cpuset_current_mems_allowed. Enclose the allocation attempts within the
cpuset seqcount retry loop so that if the cpuset changes concurrently
during allocation, the attempts are retried using the updated nodemask.
This ensures that the initial node check and fallback loop safely honor
the task's cpuset without violating cpuset constraints or causing NULL
pointer dereferences or unexpected allocation failures.
From a userspace perspective, this bug allows an unprivileged user to
crash the kernel (trigger a panic) by requesting a gigantic hugepage
allocation with MPOL_PREFERRED_MANY on a system where CMA is only
configured on a subset of NUMA nodes.
This can be reproduced by booting a VM with two NUMA nodes, restricting
CMA to Node 1 (e.g., hugetlb_cma=1:1G default_hugepagesz=1G hugepagesz=1G
hugepages=0), and running a program that allocates a 1GB hugepage area
without reserving, restricts allocation to Node 0 using mbind() with
MPOL_PREFERRED_MANY, and triggers a page fault:
void *ptr = mmap(NULL, 1UL << 30, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB |
MAP_HUGE_1GB | MAP_NORESERVE, -1, 0);
unsigned long nodemask = 1; /* Node 0 */
mbind(ptr, 1UL << 30, MPOL_PREFERRED_MANY, &nodemask,
sizeof(nodemask) * 8, 0);
memset(ptr, 0, 1UL << 30); /* Trigger fault */
This results in a NULL pointer dereference:
BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
Oops: Oops: 0000 [#1] SMP NOPTI
RIP: 0010:hugetlb_cma_alloc_frozen_folio+0x75/0x120
Call Trace:
<TASK>
only_alloc_fresh_hugetlb_folio.isra.0+0x2c/0x160
alloc_surplus_hugetlb_folio+0x6d/0x100
alloc_hugetlb_folio+0x3c5/0x660
hugetlb_no_page+0x3d9/0x650
mm/hugetlb_cma: fix null nodemask dereference in hugetlb_cma_alloc_frozen_folio
alloc_buddy_hugetlb_folio_with_mpol() can pass a NULL nodemask to
alloc_fresh_hugetlb_folio() as a fallback to allocate from all nodes. If
order is gigantic, alloc_fresh_hugetlb_folio() propagates the NULL
nodemask down to hugetlb_cma_alloc_frozen_folio() via
alloc_gigantic_frozen_folio().
Additionally, hugetlb_cma_alloc_frozen_folio() previously attempted
allocation on hugetlb_cma[nid] without verifying if nid is included in the
caller's nodemask. Adding a node_isset(nid, *nodemask) check ensures the
initial preferred node allocation honors the memory policy / nodemask.
However, hugetlb_cma_alloc_frozen_folio() dereferences the nodemask in
node_isset(nid, *nodemask) and for_each_node_mask(node, *nodemask),
leading to a null pointer dereference kernel panic when nodemask is NULL.
Fix this by checking if nodemask is NULL in
hugetlb_cma_alloc_frozen_folio() and defaulting it to
cpuset_current_mems_allowed. Enclose the allocation attempts within the
cpuset seqcount retry loop so that if the cpuset changes concurrently
during allocation, the attempts are retried using the updated nodemask.
This ensures that the initial node check and fallback loop safely honor
the task's cpuset without violating cpuset constraints or causing NULL
pointer dereferences or unexpected allocation failures.
From a userspace perspective, this bug allows an unprivileged user to
crash the kernel (trigger a panic) by requesting a gigantic hugepage
allocation with MPOL_PREFERRED_MANY on a system where CMA is only
configured on a subset of NUMA nodes.
This can be reproduced by booting a VM with two NUMA nodes, restricting
CMA to Node 1 (e.g., hugetlb_cma=1:1G default_hugepagesz=1G hugepagesz=1G
hugepages=0), and running a program that allocates a 1GB hugepage area
without reserving, restricts allocation to Node 0 using mbind() with
MPOL_PREFERRED_MANY, and triggers a page fault:
void *ptr = mmap(NULL, 1UL << 30, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB |
MAP_HUGE_1GB | MAP_NORESERVE, -1, 0);
unsigned long nodemask = 1; /* Node 0 */
mbind(ptr, 1UL << 30, MPOL_PREFERRED_MANY, &nodemask,
sizeof(nodemask) * 8, 0);
memset(ptr, 0, 1UL << 30); /* Trigger fault */
This results in a NULL pointer dereference:
BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
Oops: Oops: 0000 [#1] SMP NOPTI
RIP: 0010:hugetlb_cma_alloc_frozen_folio+0x75/0x120
Call Trace:
<TASK>
only_alloc_fresh_hugetlb_folio.isra.0+0x2c/0x160
alloc_surplus_hugetlb_folio+0x6d/0x100
alloc_hugetlb_folio+0x3c5/0x660
hugetlb_no_page+0x3d9/0x650
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
|||||||||||||||
| Linux | Linux | affected |
|
No data.
No data.
No data.
Advisories
No advisories yet.
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Wed, 16 Sep 2026 10:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: mm/hugetlb_cma: fix null nodemask dereference in hugetlb_cma_alloc_frozen_folio alloc_buddy_hugetlb_folio_with_mpol() can pass a NULL nodemask to alloc_fresh_hugetlb_folio() as a fallback to allocate from all nodes. If order is gigantic, alloc_fresh_hugetlb_folio() propagates the NULL nodemask down to hugetlb_cma_alloc_frozen_folio() via alloc_gigantic_frozen_folio(). Additionally, hugetlb_cma_alloc_frozen_folio() previously attempted allocation on hugetlb_cma[nid] without verifying if nid is included in the caller's nodemask. Adding a node_isset(nid, *nodemask) check ensures the initial preferred node allocation honors the memory policy / nodemask. However, hugetlb_cma_alloc_frozen_folio() dereferences the nodemask in node_isset(nid, *nodemask) and for_each_node_mask(node, *nodemask), leading to a null pointer dereference kernel panic when nodemask is NULL. Fix this by checking if nodemask is NULL in hugetlb_cma_alloc_frozen_folio() and defaulting it to cpuset_current_mems_allowed. Enclose the allocation attempts within the cpuset seqcount retry loop so that if the cpuset changes concurrently during allocation, the attempts are retried using the updated nodemask. This ensures that the initial node check and fallback loop safely honor the task's cpuset without violating cpuset constraints or causing NULL pointer dereferences or unexpected allocation failures. From a userspace perspective, this bug allows an unprivileged user to crash the kernel (trigger a panic) by requesting a gigantic hugepage allocation with MPOL_PREFERRED_MANY on a system where CMA is only configured on a subset of NUMA nodes. This can be reproduced by booting a VM with two NUMA nodes, restricting CMA to Node 1 (e.g., hugetlb_cma=1:1G default_hugepagesz=1G hugepagesz=1G hugepages=0), and running a program that allocates a 1GB hugepage area without reserving, restricts allocation to Node 0 using mbind() with MPOL_PREFERRED_MANY, and triggers a page fault: void *ptr = mmap(NULL, 1UL << 30, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB | MAP_HUGE_1GB | MAP_NORESERVE, -1, 0); unsigned long nodemask = 1; /* Node 0 */ mbind(ptr, 1UL << 30, MPOL_PREFERRED_MANY, &nodemask, sizeof(nodemask) * 8, 0); memset(ptr, 0, 1UL << 30); /* Trigger fault */ This results in a NULL pointer dereference: BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page Oops: Oops: 0000 [#1] SMP NOPTI RIP: 0010:hugetlb_cma_alloc_frozen_folio+0x75/0x120 Call Trace: <TASK> only_alloc_fresh_hugetlb_folio.isra.0+0x2c/0x160 alloc_surplus_hugetlb_folio+0x6d/0x100 alloc_hugetlb_folio+0x3c5/0x660 hugetlb_no_page+0x3d9/0x650 | |
| Title | mm/hugetlb_cma: fix null nodemask dereference in hugetlb_cma_alloc_frozen_folio | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
Projects
Sign in to view the affected projects.
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-09-16T10:32:47.482Z
Reserved: 2026-09-11T19:38:34.778Z
Link: CVE-2026-89966
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-16T11:17:07.160
Modified: 2026-09-16T11:17:07.160
Link: CVE-2026-89966
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.