CVE-2025-39775
- Source
- https://nvd.nist.gov/vuln/detail/CVE-2025-39775
- Import Source
- https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2025-39775.json
- JSON Data
- https://api.test.osv.dev/v1/vulns/CVE-2025-39775
- Downstream
- Published
- 2025-09-11T16:56:28.230Z
- Modified
- 2025-12-02T18:47:58.070144Z
- Summary
- mm/mremap: fix WARN with uffd that has remap events disabled
- Details
-
In the Linux kernel, the following vulnerability has been resolved:
mm/mremap: fix WARN with uffd that has remap events disabled
Registering userfaultd on a VMA that spans at least one PMD and then mremap()'ing that VMA can trigger a WARN when recovering from a failed page table move due to a page table allocation error.
The code ends up doing the right thing (recurse, avoiding moving actual page tables), but triggering that WARN is unpleasant:
WARNING: CPU: 2 PID: 6133 at mm/mremap.c:357 movenormalpmd mm/mremap.c:357 [inline] WARNING: CPU: 2 PID: 6133 at mm/mremap.c:357 movepgtentry mm/mremap.c:595 [inline] WARNING: CPU: 2 PID: 6133 at mm/mremap.c:357 movepagetables+0x3832/0x44a0 mm/mremap.c:852 Modules linked in: CPU: 2 UID: 0 PID: 6133 Comm: syz.0.19 Not tainted 6.17.0-rc1-syzkaller-00004-g53e760d89498 #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 RIP: 0010:movenormalpmd mm/mremap.c:357 [inline] RIP: 0010:movepgtentry mm/mremap.c:595 [inline] RIP: 0010:movepagetables+0x3832/0x44a0 mm/mremap.c:852 Code: ... RSP: 0018:ffffc900037a76d8 EFLAGS: 00010293 RAX: 0000000000000000 RBX: 0000000032930007 RCX: ffffffff820c6645 RDX: ffff88802e56a440 RSI: ffffffff820c7201 RDI: 0000000000000007 RBP: ffff888037728fc0 R08: 0000000000000007 R09: 0000000000000000 R10: 0000000032930007 R11: 0000000000000000 R12: 0000000000000000 R13: ffffc900037a79a8 R14: 0000000000000001 R15: dffffc0000000000 FS: 000055556316a500(0000) GS:ffff8880d68bc000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000001b30863fff CR3: 0000000050171000 CR4: 0000000000352ef0 Call Trace: <TASK> copyvmaanddata+0x468/0x790 mm/mremap.c:1215 movevma+0x548/0x1780 mm/mremap.c:1282 mremapto+0x1b7/0x450 mm/mremap.c:1406 domremap+0xfad/0x1f80 mm/mremap.c:1921 _dosysmremap+0x119/0x170 mm/mremap.c:1977 dosyscallx64 arch/x86/entry/syscall64.c:63 [inline] dosyscall64+0xcd/0x4c0 arch/x86/entry/syscall64.c:94 entrySYSCALL64afterhwframe+0x77/0x7f RIP: 0033:0x7f00d0b8ebe9 Code: ... RSP: 002b:00007ffe5ea5ee98 EFLAGS: 00000246 ORIGRAX: 0000000000000019 RAX: ffffffffffffffda RBX: 00007f00d0db5fa0 RCX: 00007f00d0b8ebe9 RDX: 0000000000400000 RSI: 0000000000c00000 RDI: 0000200000000000 RBP: 00007ffe5ea5eef0 R08: 0000200000c00000 R09: 0000000000000000 R10: 0000000000000003 R11: 0000000000000246 R12: 0000000000000002 R13: 00007f00d0db5fa0 R14: 00007f00d0db5fa0 R15: 0000000000000005 </TASK>
The underlying issue is that we recurse during the original page table move, but not during the recovery move.
Fix it by checking for both VMAs and performing the check before the pmd_none() sanity check.
Add a new helper where we perform+document that check for the PMD and PUD level.
Thanks to Harry for bisecting.
- Database specific
{ "cna_assigner": "Linux", "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/39xxx/CVE-2025-39775.json" }- References
-
- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
- https://git.kernel.org/stable/c/772e5b4a5e8360743645b9a466842d16092c4f94
- https://git.kernel.org/stable/c/d70ca21f7bff162a5afae1ddd6f4107adf05ae23
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/39xxx/CVE-2025-39775.json
- https://nvd.nist.gov/vuln/detail/CVE-2025-39775
Affected packages
Git / git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Affected ranges
- Type
- GIT
- Repo
- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
- Events
-
Introduced0cef0bb836e3cfe00f08f9606c72abd72fe78ca3Fixedd70ca21f7bff162a5afae1ddd6f4107adf05ae23Fixed772e5b4a5e8360743645b9a466842d16092c4f94
- Type
- GIT
- Repo
- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
- Events
-
Introduced0 Unknown introduced commit / All previous commits are affectedLast affected310ac886d68de661c3a334198d8604b722d7fdf8