CVE-2026-74518

Status: UPDATED  |  Advisory ID: CVE-2026-74518

Key Details

Affected Products, Subsystems & Sectors

What to Know

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

mm/hugetlb: fix list corruption in allocate_file_region_entries()

allocate_file_region_entries() tops up resv->region_cache with freshly

allocated file_region descriptors. The allocation uses GFP_KERNEL, so

resv->lock is dropped around it: the new entries are gathered on a

stack-local list head, allocated_regions, and spliced into

resv->region_cache once the lock is re-acquired.

The splice used list_splice(), which moves the entries but does not

re-initialize the source head, so allocated_regions is left pointing at an

entry that now lives on resv->region_cache. The top-up runs in a while

loop that re-checks the cache deficit after re-acquiring the lock. For a

shared mapping the resv_map is shared by every mapper of the hugetlbfs

inode, so a concurrent region_chg()/region_add()/region_del() on the same

resv_map can consume cache entries during the unlocked window and force a

second iteration. That iteration calls list_add() on the stale head and

corrupts the list; with CONFIG_DEBUG_LIST the __list_add_valid() check

trips:

list_add corruption. next->prev should be prev (ffffc900011ff7f8),

but was ffff88814c281460. (next=ffff88814c545640).

kernel BUG at lib/list_debug.c:31!

allocate_file_region_entries+0x191/0x420

region_chg+0x267/0x300

hugetlb_reserve_pages+0x387/0xc80

hugetlbfs_file_mmap+0x2ce/0x3f0

mmap_region+0x1348/0x1a80

do_mmap+0x85e/0xb90

vm_mmap_pgoff+0x18c/0x330

ksys_mmap_pgoff+0x2a1/0x3e0

do_syscall_64+0xd7/0x420

Without CONFIG_DEBUG_LIST the bad list_add() silently links a kernel-stack

address into resv->region_cache, leading to later use-after-free.

This was observed as a real host panic on a dense KVM host where a QEMU

guest-RAM hugetlbfs file was mapped MAP_SHARED by both QEMU and a separate

SPDK/DPDK vhost-user target, generating concurrent region_* traffic on one

shared resv_map.

Use list_splice_init() so the source head is re-initialized empty after

each splice, making the retry loop safe. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References