{"id":"CVE-2025-39775","title":"mm/mremap: fix WARN with uffd that has remap events disabled","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm/mremap: fix WARN with uffd that has remap events disabled\n\nRegistering userfaultd on a VMA that spans at least one PMD and then\nmremap()'ing that VMA can trigger a W…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 310ac886d68de661c3a334198d8604b722d7fdf8 < 1c15b4cd3a97aea013bdb18d9a55ca0384fbb8d4","Linux >= 0cef0bb836e3cfe00f08f9606c72abd72fe78ca3 < d70ca21f7bff162a5afae1ddd6f4107adf05ae23","Linux >= 0cef0bb836e3cfe00f08f9606c72abd72fe78ca3 < 772e5b4a5e8360743645b9a466842d16092c4f94","Linux 8e2f6ba256dd1e590addc48e6e9577bf39c482f2","Linux >= 6.12.11 < 6.12.114","Linux >= 6.6.160 < 6.7","Linux 6.13"],"published":"2025-09-11","updated":"2026-10-21","sourceUpdated":"2026-10-21T12:37:20.574Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2025-39775","references":[{"url":"https://git.kernel.org/stable/c/1c15b4cd3a97aea013bdb18d9a55ca0384fbb8d4"},{"url":"https://git.kernel.org/stable/c/d70ca21f7bff162a5afae1ddd6f4107adf05ae23"},{"url":"https://git.kernel.org/stable/c/772e5b4a5e8360743645b9a466842d16092c4f94"}],"tags":["cve.org"],"epss":0.00187,"epssPercentile":0.0824,"ingestedAt":"2026-10-21T12:48:53.699Z","slug":"CVE-2025-39775","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nmm/mremap: fix WARN with uffd that has remap events disabled\n\nRegistering userfaultd on a VMA that spans at least one PMD and then\nmremap()'ing that VMA can trigger a WARN when recovering from a failed\npage table move due to a page table allocation error.\n\nThe code ends up doing the right thing (recurse, avoiding moving actual\npage tables), but triggering that WARN is unpleasant:\n\nWARNING: CPU: 2 PID: 6133 at mm/mremap.c:357 move_normal_pmd mm/mremap.c:357 [inline]\nWARNING: CPU: 2 PID: 6133 at mm/mremap.c:357 move_pgt_entry mm/mremap.c:595 [inline]\nWARNING: CPU: 2 PID: 6133 at mm/mremap.c:357 move_page_tables+0x3832/0x44a0 mm/mremap.c:852\nModules linked in:\nCPU: 2 UID: 0 PID: 6133 Comm: syz.0.19 Not tainted 6.17.0-rc1-syzkaller-00004-g53e760d89498 #0 PREEMPT(full)\nHardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014\nRIP: 0010:move_normal_pmd mm/mremap.c:357 [inline]\nRIP: 0010:move_pgt_entry mm/mremap.c:595 [inline]\nRIP: 0010:move_page_tables+0x3832/0x44a0 mm/mremap.c:852\nCode: ...\nRSP: 0018:ffffc900037a76d8 EFLAGS: 00010293\nRAX: 0000000000000000 RBX: 0000000032930007 RCX: ffffffff820c6645\nRDX: ffff88802e56a440 RSI: ffffffff820c7201 RDI: 0000000000000007\nRBP: ffff888037728fc0 R08: 0000000000000007 R09: 0000000000000000\nR10: 0000000032930007 R11: 0000000000000000 R12: 0000000000000000\nR13: ffffc900037a79a8 R14: 0000000000000001 R15: dffffc0000000000\nFS:  000055556316a500(0000) GS:ffff8880d68bc000(0000) knlGS:0000000000000000\nCS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\nCR2: 0000001b30863fff CR3: 0000000050171000 CR4: 0000000000352ef0\nCall Trace:\n <TASK>\n copy_vma_and_data+0x468/0x790 mm/mremap.c:1215\n move_vma+0x548/0x1780 mm/mremap.c:1282\n mremap_to+0x1b7/0x450 mm/mremap.c:1406\n do_mremap+0xfad/0x1f80 mm/mremap.c:1921\n __do_sys_mremap+0x119/0x170 mm/mremap.c:1977\n do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]\n do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94\n entry_SYSCALL_64_after_hwframe+0x77/0x7f\nRIP: 0033:0x7f00d0b8ebe9\nCode: ...\nRSP: 002b:00007ffe5ea5ee98 EFLAGS: 00000246 ORIG_RAX: 0000000000000019\nRAX: ffffffffffffffda RBX: 00007f00d0db5fa0 RCX: 00007f00d0b8ebe9\nRDX: 0000000000400000 RSI: 0000000000c00000 RDI: 0000200000000000\nRBP: 00007ffe5ea5eef0 R08: 0000200000c00000 R09: 0000000000000000\nR10: 0000000000000003 R11: 0000000000000246 R12: 0000000000000002\nR13: 00007f00d0db5fa0 R14: 00007f00d0db5fa0 R15: 0000000000000005\n </TASK>\n\nThe underlying issue is that we recurse during the original page table\nmove, but not during the recovery move.\n\nFix it by checking for both VMAs and performing the check before the\npmd_none() sanity check.\n\nAdd a new helper where we perform+document that check for the PMD and PUD\nlevel.\n\nThanks to Harry for bisecting.\n\n## Affected\n\n- `Linux >= 310ac886d68de661c3a334198d8604b722d7fdf8 < 1c15b4cd3a97aea013bdb18d9a55ca0384fbb8d4`\n- `Linux >= 0cef0bb836e3cfe00f08f9606c72abd72fe78ca3 < d70ca21f7bff162a5afae1ddd6f4107adf05ae23`\n- `Linux >= 0cef0bb836e3cfe00f08f9606c72abd72fe78ca3 < 772e5b4a5e8360743645b9a466842d16092c4f94`\n- `Linux 8e2f6ba256dd1e590addc48e6e9577bf39c482f2`\n- `Linux >= 6.12.11 < 6.12.114`\n- `Linux >= 6.6.160 < 6.7`\n- `Linux 6.13`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}