{"id":"CVE-2022-49760","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm/hugetlb: fix PTE marker handling in hugetlb_change_protection()\n\nPatch series \"mm/hugetlb: uffd-wp fixes for hugetlb_change_protection()\".\n\nPlaying with virtio-mem a…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm/hugetlb: fix PTE marker handling in hugetlb_change_protection()\n\nPatch series \"mm/hugetlb: uffd-wp fixes for hugetlb_change_protection()\".\n\nPlaying 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","slug":"CVE-2022-49760","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nmm/hugetlb: fix PTE marker handling in hugetlb_change_protection()\n\nPatch series \"mm/hugetlb: uffd-wp fixes for hugetlb_change_protection()\".\n\nPlaying with virtio-mem and background snapshots (using uffd-wp) on\nhugetlb in QEMU, I managed to trigger a VM_BUG_ON().  Looking into the\ndetails, hugetlb_change_protection() seems to not handle uffd-wp correctly\nin all cases.\n\nPatch #1 fixes my test case.  I don't have reproducers for patch #2, as it\nrequires running into migration entries.\n\nI did not yet check in detail yet if !hugetlb code requires similar care.\n\n\nThis patch (of 2):\n\nThere are two problematic cases when stumbling over a PTE marker in\nhugetlb_change_protection():\n\n(1) We protect an uffd-wp PTE marker a second time using uffd-wp: we will\n    end up in the \"!huge_pte_none(pte)\" case and mess up the PTE marker.\n\n(2) We unprotect a uffd-wp PTE marker: we will similarly end up in the\n    \"!huge_pte_none(pte)\" case even though we cleared the PTE, because\n    the \"pte\" variable is stale. We'll mess up the PTE marker.\n\nFor example, if we later stumble over such a \"wrongly modified\" PTE marker,\nwe'll treat it like a present PTE that maps some garbage page.\n\nThis can, for example, be triggered by mapping a memfd backed by huge\npages, registering uffd-wp, uffd-wp'ing an unmapped page and (a)\nuffd-wp'ing it a second time; or (b) uffd-unprotecting it; or (c)\nunregistering uffd-wp. Then, ff we trigger fallocate(FALLOC_FL_PUNCH_HOLE)\non that file range, we will run into a VM_BUG_ON:\n\n[  195.039560] page:00000000ba1f2987 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x0\n[  195.039565] flags: 0x7ffffc0001000(reserved|node=0|zone=0|lastcpupid=0x1fffff)\n[  195.039568] raw: 0007ffffc0001000 ffffe742c0000008 ffffe742c0000008 0000000000000000\n[  195.039569] raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000\n[  195.039569] page dumped because: VM_BUG_ON_PAGE(compound && !PageHead(page))\n[  195.039573] ------------[ cut here ]------------\n[  195.039574] kernel BUG at mm/rmap.c:1346!\n[  195.039579] invalid opcode: 0000 [#1] PREEMPT SMP NOPTI\n[  195.039581] CPU: 7 PID: 4777 Comm: qemu-system-x86 Not tainted 6.0.12-200.fc36.x86_64 #1\n[  195.039583] Hardware name: LENOVO 20WNS1F81N/20WNS1F81N, BIOS N35ET50W (1.50 ) 09/15/2022\n[  195.039584] RIP: 0010:page_remove_rmap+0x45b/0x550\n[  195.039588] Code: [...]\n[  195.039589] RSP: 0018:ffffbc03c3633ba8 EFLAGS: 00010292\n[  195.039591] RAX: 0000000000000040 RBX: ffffe742c0000000 RCX: 0000000000000000\n[  195.039592] RDX: 0000000000000002 RSI: ffffffff8e7aac1a RDI: 00000000ffffffff\n[  195.039592] RBP: 0000000000000001 R08: 0000000000000000 R09: ffffbc03c3633a08\n[  195.039593] R10: 0000000000000003 R11: ffffffff8f146328 R12: ffff9b04c42754b0\n[  195.039594] R13: ffffffff8fcc6328 R14: ffffbc03c3633c80 R15: ffff9b0484ab9100\n[  195.039595] FS:  00007fc7aaf68640(0000) GS:ffff9b0bbf7c0000(0000) knlGS:0000000000000000\n[  195.039596] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n[  195.039597] CR2: 000055d402c49110 CR3: 0000000159392003 CR4: 0000000000772ee0\n[  195.039598] PKRU: 55555554\n[  195.039599] Call Trace:\n[  195.039600]  <TASK>\n[  195.039602]  __unmap_hugepage_range+0x33b/0x7d0\n[  195.039605]  unmap_hugepage_range+0x55/0x70\n[  195.039608]  hugetlb_vmdelete_list+0x77/0xa0\n[  195.039611]  hugetlbfs_fallocate+0x410/0x550\n[  195.039612]  ? _raw_spin_unlock_irqrestore+0x23/0x40\n[  195.039616]  vfs_fallocate+0x12e/0x360\n[  195.039618]  __x64_sys_fallocate+0x40/0x70\n[  195.039620]  do_syscall_64+0x58/0x80\n[  195.039623]  ? syscall_exit_to_user_mode+0x17/0x40\n[  195.039624]  ? do_syscall_64+0x67/0x80\n[  195.039626]  entry_SYSCALL_64_after_hwframe+0x63/0xcd\n[  195.039628] RIP: 0033:0x7fc7b590651f\n[  195.039653] Code: [...]\n[  195.039654] RSP: 002b:00007fc7aaf66e70 EFLAGS: 00000293 ORIG_RAX: 000000000000011d\n[  195.039655] RAX: ffffffffffffffda RBX: 0000558ef4b7f370 RCX: 00007fc7b590651f\n---truncated---\n\n## Affected\n\n- `linux_kernel >= 5.19, < 6.1.8`\n- `linux_kernel = 6.2`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `linux_kernel 6.1.8`\n\n## Vendor advisories\n\n- **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)","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":230005,"id":"CVE-2022-49760","ts":1793124768414,"field":"cvss","old":"4.1","new":"7.8"},{"seq":230004,"id":"CVE-2022-49760","ts":1793124768414,"field":"severity","old":"medium","new":"high"},{"seq":223765,"id":"CVE-2022-49760","ts":1792238395380,"field":"cvss","old":"7.8","new":"4.1"},{"seq":223764,"id":"CVE-2022-49760","ts":1792238395380,"field":"severity","old":"high","new":"medium"}]}