CVE-2026-64131 mm/memory: fix spurious warning when unmapping device-private/exclusive pages
In the Linux kernel, the following vulnerability has been resolved:

mm/memory: fix spurious warning when unmapping device-private/exclusive pages

Device private and exclusive entries are only supported for anonymous
folios.  This condition is tested in __migrate_device_pages() and
make_device_exclusive() using folio_test_anon().  However the unmap path
tests this assumption using vma_is_anonymous().

This is wrong because whilst anonymous VMAs can only contain folios where
folio_test_anon() is true the opposite relation does not hold.  A folio
for which folio_test_anon() is true does not imply vma_is_anonymous() is
true.  Such a condition can occur if for example a folio is part of a
private filebacked mapping.

In this case vma_is_anonymous() is false as the mapping is filebacked, but
folio_test_anon() may be true, thus permitting devices to migrate the
folio to device private memory.  This can lead to the following spurious
warnings during process teardown:

[  772.737706] ------------[ cut here ]------------
[  772.739201] WARNING: mm/memory.c:1754 at unmap_page_range.cold+0x26/0x18a, CPU#17: hmm-tests/2041
[  772.742050] Modules linked in: test_hmm nvidia_uvm(O) nvidia(O)
[  772.743959] CPU: 17 UID: 0 PID: 2041 Comm: hmm-tests Tainted: G        W  O        7.0.0+ #387 PREEMPT(full)
[  772.747104] Tainted: [W]=WARN, [O]=OOT_MODULE
[  772.748509] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.17.0-0-gb52ca86e094d-prebuilt.qemu.org 04/01/2014
[  772.752117] RIP: 0010:unmap_page_range.cold+0x26/0x18a
[  772.753780] Code: 7e fe ff ff 48 89 4c 24 78 4c 89 44 24 38 e8 f2 ff b1 00 48 8b 4c 24 78 4c 8b 44 24 38 48 8b 44 24 18 48 83 78 48 00 74 04 90 <0f> 0b 90 48 89 ca b8 ff ff 37 00 48 c1 ea 03 48 c1 e0 2a 80 3c 02
[  772.759602] RSP: 0018:ffff888112607550 EFLAGS: 00010286
[  772.761310] RAX: ffff88811bbf4dc0 RBX: dffffc0000000000 RCX: ffffea03e9bfffd8
[  772.763583] RDX: 1ffff1102377e9c1 RSI: 0000000000000008 RDI: ffff88811bbf4e08
[  772.765914] RBP: 0000000000000006 R08: ffff8881059f7448 R09: ffffed10224c0e68
[  772.768184] R10: ffff888112607347 R11: 0000000000000001 R12: 0000000000000001
[  772.770461] R13: ffffea03e9bfffc0 R14: ffff888112607908 R15: ffffea03e9bfffc0
[  772.772782] FS:  00007f327caa2780(0000) GS:ffff888427b7d000(0000) knlGS:0000000000000000
[  772.775328] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  772.777187] CR2: 00007f327ca89000 CR3: 00000001994d5000 CR4: 00000000000006f0
[  772.779135] Call Trace:
[  772.779792]  <TASK>
[  772.780317]  ? dmirror_interval_invalidate+0x1a3/0x290 [test_hmm]
[  772.781873]  ? vm_normal_page_pud+0x2b0/0x2b0
[  772.782992]  ? __rwlock_init+0x150/0x150
[  772.784006]  ? lock_release+0x216/0x2b0
[  772.785008]  ? __mmu_notifier_invalidate_range_start+0x505/0x6e0
[  772.786522]  ? lock_release+0x216/0x2b0
[  772.787498]  ? unmap_single_vma+0xb6/0x210
[  772.788573]  unmap_vmas+0x27d/0x520
[  772.789506]  ? unmap_single_vma+0x210/0x210
[  772.790607]  ? mas_update_gap.part.0+0x620/0x620
[  772.791834]  unmap_region+0x19e/0x350
[  772.792769]  ? remove_vma+0x130/0x130
[  772.793684]  ? mas_alloc_nodes+0x1f2/0x300
[  772.794730]  vms_complete_munmap_vmas+0x8c1/0xe20
[  772.795926]  ? unmap_region+0x350/0x350
[  772.796917]  do_vmi_align_munmap+0x36a/0x4e0
[  772.798018]  ? lock_release+0x216/0x2b0
[  772.799024]  ? vma_shrink+0x620/0x620
[  772.799983]  do_vmi_munmap+0x150/0x2c0
[  772.800939]  __vm_munmap+0x161/0x2c0
[  772.801872]  ? expand_downwards+0xd60/0xd60
[  772.802948]  ? clockevents_program_event+0x1ef/0x540
[  772.804217]  ? lock_release+0x216/0x2b0
[  772.805158]  __x64_sys_munmap+0x59/0x80
[  772.805776]  do_syscall_64+0xfc/0x670
[  772.806336]  ? irqentry_exit+0xda/0x580
[  772.806976]  entry_SYSCALL_64_after_hwframe+0x4b/0x53
[  772.807772] RIP: 0033:0x7f327cbb2717
[  772.808323] Code: 73 01 c3 48 8b 0d f9 76 0d 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 0b 00 00 00 0f 05 <48> 3d 01 f0 ff
---truncated---
CVSS v3.1 score: 5.5