--- id: CVE-2022-49760 title: |- In the Linux kernel, the following vulnerability has been resolved: mm/hugetlb: fix PTE marker handling in hugetlb_change_protection() Patch series "mm/hugetlb: uffd-wp fixes for hugetlb_change_protection()". Playing with virtio-mem a… summary: |- In the Linux kernel, the following vulnerability has been resolved: mm/hugetlb: fix PTE marker handling in hugetlb_change_protection() Patch series "mm/hugetlb: uffd-wp fixes for hugetlb_change_protection()". Playing with virtio-mem a… severity: high cvss: 7.8 cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H' cwe: - CWE-665 vendor: linux product: linux_kernel affected: - 'linux_kernel >= 5.19, < 6.1.8' - linux_kernel = 6.2 patched: - linux_kernel 6.1.8 published: '2025-03-27' updated: '2026-10-15' sourceUpdated: '2026-10-15T22:17:25.033' source: NVD sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2022-49760' references: - url: 'https://git.kernel.org/stable/c/0e678153f5be7e6c8d28835f5a678618da4b7a9c' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/6062c992e912df1eedad52cf64efb3d48e8d35c5' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: >- https://security.access.redhat.com/data/csaf/v2/vex/2022/cve-2022-49760.json - url: 'https://access.redhat.com/security/cve/CVE-2022-49760' - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2355517' - url: 'https://www.cve.org/CVERecord?id=CVE-2022-49760' - url: 'https://nvd.nist.gov/vuln/detail/CVE-2022-49760' - url: >- https://lore.kernel.org/linux-cve-announce/2025032703-CVE-2022-49760-97be@gregkh/T tags: - nvd - csaf - vex - red-hat - cve.org - score-dispute epss: 0.00173 epssPercentile: 0.06608 ssvc: exploitation: none automatable: 'no' technicalImpact: total timestamp: '2026-10-15T21:18:16.874914Z' scores: nvd: 7.8 vendor: 4.1 cna: 7.8 ingestedAt: '2026-10-15T21:45:11.288Z' --- ## Overview In the Linux kernel, the following vulnerability has been resolved: mm/hugetlb: fix PTE marker handling in hugetlb_change_protection() Patch series "mm/hugetlb: uffd-wp fixes for hugetlb_change_protection()". Playing with virtio-mem and background snapshots (using uffd-wp) on hugetlb in QEMU, I managed to trigger a VM_BUG_ON(). Looking into the details, hugetlb_change_protection() seems to not handle uffd-wp correctly in all cases. Patch #1 fixes my test case. I don't have reproducers for patch #2, as it requires running into migration entries. I did not yet check in detail yet if !hugetlb code requires similar care. This patch (of 2): There are two problematic cases when stumbling over a PTE marker in hugetlb_change_protection(): (1) We protect an uffd-wp PTE marker a second time using uffd-wp: we will end up in the "!huge_pte_none(pte)" case and mess up the PTE marker. (2) We unprotect a uffd-wp PTE marker: we will similarly end up in the "!huge_pte_none(pte)" case even though we cleared the PTE, because the "pte" variable is stale. We'll mess up the PTE marker. For example, if we later stumble over such a "wrongly modified" PTE marker, we'll treat it like a present PTE that maps some garbage page. This can, for example, be triggered by mapping a memfd backed by huge pages, registering uffd-wp, uffd-wp'ing an unmapped page and (a) uffd-wp'ing it a second time; or (b) uffd-unprotecting it; or (c) unregistering uffd-wp. Then, ff we trigger fallocate(FALLOC_FL_PUNCH_HOLE) on that file range, we will run into a VM_BUG_ON: [ 195.039560] page:00000000ba1f2987 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x0 [ 195.039565] flags: 0x7ffffc0001000(reserved|node=0|zone=0|lastcpupid=0x1fffff) [ 195.039568] raw: 0007ffffc0001000 ffffe742c0000008 ffffe742c0000008 0000000000000000 [ 195.039569] raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000 [ 195.039569] page dumped because: VM_BUG_ON_PAGE(compound && !PageHead(page)) [ 195.039573] ------------[ cut here ]------------ [ 195.039574] kernel BUG at mm/rmap.c:1346! [ 195.039579] invalid opcode: 0000 [#1] PREEMPT SMP NOPTI [ 195.039581] CPU: 7 PID: 4777 Comm: qemu-system-x86 Not tainted 6.0.12-200.fc36.x86_64 #1 [ 195.039583] Hardware name: LENOVO 20WNS1F81N/20WNS1F81N, BIOS N35ET50W (1.50 ) 09/15/2022 [ 195.039584] RIP: 0010:page_remove_rmap+0x45b/0x550 [ 195.039588] Code: [...] [ 195.039589] RSP: 0018:ffffbc03c3633ba8 EFLAGS: 00010292 [ 195.039591] RAX: 0000000000000040 RBX: ffffe742c0000000 RCX: 0000000000000000 [ 195.039592] RDX: 0000000000000002 RSI: ffffffff8e7aac1a RDI: 00000000ffffffff [ 195.039592] RBP: 0000000000000001 R08: 0000000000000000 R09: ffffbc03c3633a08 [ 195.039593] R10: 0000000000000003 R11: ffffffff8f146328 R12: ffff9b04c42754b0 [ 195.039594] R13: ffffffff8fcc6328 R14: ffffbc03c3633c80 R15: ffff9b0484ab9100 [ 195.039595] FS: 00007fc7aaf68640(0000) GS:ffff9b0bbf7c0000(0000) knlGS:0000000000000000 [ 195.039596] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 195.039597] CR2: 000055d402c49110 CR3: 0000000159392003 CR4: 0000000000772ee0 [ 195.039598] PKRU: 55555554 [ 195.039599] Call Trace: [ 195.039600] [ 195.039602] __unmap_hugepage_range+0x33b/0x7d0 [ 195.039605] unmap_hugepage_range+0x55/0x70 [ 195.039608] hugetlb_vmdelete_list+0x77/0xa0 [ 195.039611] hugetlbfs_fallocate+0x410/0x550 [ 195.039612] ? _raw_spin_unlock_irqrestore+0x23/0x40 [ 195.039616] vfs_fallocate+0x12e/0x360 [ 195.039618] __x64_sys_fallocate+0x40/0x70 [ 195.039620] do_syscall_64+0x58/0x80 [ 195.039623] ? syscall_exit_to_user_mode+0x17/0x40 [ 195.039624] ? do_syscall_64+0x67/0x80 [ 195.039626] entry_SYSCALL_64_after_hwframe+0x63/0xcd [ 195.039628] RIP: 0033:0x7fc7b590651f [ 195.039653] Code: [...] [ 195.039654] RSP: 002b:00007fc7aaf66e70 EFLAGS: 00000293 ORIG_RAX: 000000000000011d [ 195.039655] RAX: ffffffffffffffda RBX: 0000558ef4b7f370 RCX: 00007fc7b590651f ---truncated--- ## Affected - `linux_kernel >= 5.19, < 6.1.8` - `linux_kernel = 6.2` ## Remediation Upgrade past the affected range: - `linux_kernel 6.1.8` ## Vendor advisories - **Red Hat VEX** · Low · affected: Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 9 · updated 2026-10-16 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2022/cve-2022-49760.json)