GHSA-84V6-6VMQ-3V62
Vulnerability from github – Published: 2025-09-11 18:35 – Updated: 2026-05-12 15:31In the Linux kernel, the following vulnerability has been resolved:
mm/debug_vm_pgtable: clear page table entries at destroy_args()
The mm/debug_vm_pagetable test allocates manually page table entries for the tests it runs, using also its manually allocated mm_struct. That in itself is ok, but when it exits, at destroy_args() it fails to clear those entries with the *_clear functions.
The problem is that leaves stale entries. If another process allocates an mm_struct with a pgd at the same address, it may end up running into the stale entry. This is happening in practice on a debug kernel with CONFIG_DEBUG_VM_PGTABLE=y, for example this is the output with some extra debugging I added (it prints a warning trace if pgtables_bytes goes negative, in addition to the warning at check_mm() function):
[ 2.539353] debug_vm_pgtable: [get_random_vaddr ]: random_vaddr is 0x7ea247140000 [ 2.539366] kmem_cache info [ 2.539374] kmem_cachep 0x000000002ce82385 - freelist 0x0000000000000000 - offset 0x508 [ 2.539447] debug_vm_pgtable: [init_args ]: args->mm is 0x000000002267cc9e (...) [ 2.552800] WARNING: CPU: 5 PID: 116 at include/linux/mm.h:2841 free_pud_range+0x8bc/0x8d0 [ 2.552816] Modules linked in: [ 2.552843] CPU: 5 UID: 0 PID: 116 Comm: modprobe Not tainted 6.12.0-105.debug_vm2.el10.ppc64le+debug #1 VOLUNTARY [ 2.552859] Hardware name: IBM,9009-41A POWER9 (architected) 0x4e0202 0xf000005 of:IBM,FW910.00 (VL910_062) hv:phyp pSeries [ 2.552872] NIP: c0000000007eef3c LR: c0000000007eef30 CTR: c0000000003d8c90 [ 2.552885] REGS: c0000000622e73b0 TRAP: 0700 Not tainted (6.12.0-105.debug_vm2.el10.ppc64le+debug) [ 2.552899] MSR: 800000000282b033 CR: 24002822 XER: 0000000a [ 2.552954] CFAR: c0000000008f03f0 IRQMASK: 0 [ 2.552954] GPR00: c0000000007eef30 c0000000622e7650 c000000002b1ac00 0000000000000001 [ 2.552954] GPR04: 0000000000000008 0000000000000000 c0000000007eef30 ffffffffffffffff [ 2.552954] GPR08: 00000000ffff00f5 0000000000000001 0000000000000048 0000000000004000 [ 2.552954] GPR12: 00000003fa440000 c000000017ffa300 c0000000051d9f80 ffffffffffffffdb [ 2.552954] GPR16: 0000000000000000 0000000000000008 000000000000000a 60000000000000e0 [ 2.552954] GPR20: 4080000000000000 c0000000113af038 00007fffcf130000 0000700000000000 [ 2.552954] GPR24: c000000062a6a000 0000000000000001 8000000062a68000 0000000000000001 [ 2.552954] GPR28: 000000000000000a c000000062ebc600 0000000000002000 c000000062ebc760 [ 2.553170] NIP [c0000000007eef3c] free_pud_range+0x8bc/0x8d0 [ 2.553185] LR [c0000000007eef30] free_pud_range+0x8b0/0x8d0 [ 2.553199] Call Trace: [ 2.553207] [c0000000622e7650] [c0000000007eef30] free_pud_range+0x8b0/0x8d0 (unreliable) [ 2.553229] [c0000000622e7750] [c0000000007f40b4] free_pgd_range+0x284/0x3b0 [ 2.553248] [c0000000622e7800] [c0000000007f4630] free_pgtables+0x450/0x570 [ 2.553274] [c0000000622e78e0] [c0000000008161c0] exit_mmap+0x250/0x650 [ 2.553292] [c0000000622e7a30] [c0000000001b95b8] __mmput+0x98/0x290 [ 2.558344] [c0000000622e7a80] [c0000000001d1018] exit_mm+0x118/0x1b0 [ 2.558361] [c0000000622e7ac0] [c0000000001d141c] do_exit+0x2ec/0x870 [ 2.558376] [c0000000622e7b60] [c0000000001d1ca8] do_group_exit+0x88/0x150 [ 2.558391] [c0000000622e7bb0] [c0000000001d1db8] sys_exit_group+0x48/0x50 [ 2.558407] [c0000000622e7be0] [c00000000003d810] system_call_exception+0x1e0/0x4c0 [ 2.558423] [c0000000622e7e50] [c00000000000d05c] system_call_vectored_common+0x15c/0x2ec (...) [ 2.558892] ---[ end trace 0000000000000000 ]--- [ 2.559022] BUG: Bad rss-counter state mm:000000002267cc9e type:MM_ANONPAGES val:1 [ 2.559037] BUG: non-zero pgtables_bytes on freeing mm: -6144
Here the modprobe process ended up with an allocated mm_struct from the mm_struct slab that was used before by the debug_vm_pgtable test. That is not a problem, since the mm_stru ---truncated---
{
"affected": [],
"aliases": [
"CVE-2025-39776"
],
"database_specific": {
"cwe_ids": [
"CWE-416"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-09-11T17:15:43Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/debug_vm_pgtable: clear page table entries at destroy_args()\n\nThe mm/debug_vm_pagetable test allocates manually page table entries for\nthe tests it runs, using also its manually allocated mm_struct. That in\nitself is ok, but when it exits, at destroy_args() it fails to clear those\nentries with the *_clear functions.\n\nThe problem is that leaves stale entries. If another process allocates an\nmm_struct with a pgd at the same address, it may end up running into the\nstale entry. This is happening in practice on a debug kernel with\nCONFIG_DEBUG_VM_PGTABLE=y, for example this is the output with some extra\ndebugging I added (it prints a warning trace if pgtables_bytes goes\nnegative, in addition to the warning at check_mm() function):\n\n[ 2.539353] debug_vm_pgtable: [get_random_vaddr ]: random_vaddr is 0x7ea247140000\n[ 2.539366] kmem_cache info\n[ 2.539374] kmem_cachep 0x000000002ce82385 - freelist 0x0000000000000000 - offset 0x508\n[ 2.539447] debug_vm_pgtable: [init_args ]: args-\u003emm is 0x000000002267cc9e\n(...)\n[ 2.552800] WARNING: CPU: 5 PID: 116 at include/linux/mm.h:2841 free_pud_range+0x8bc/0x8d0\n[ 2.552816] Modules linked in:\n[ 2.552843] CPU: 5 UID: 0 PID: 116 Comm: modprobe Not tainted 6.12.0-105.debug_vm2.el10.ppc64le+debug #1 VOLUNTARY\n[ 2.552859] Hardware name: IBM,9009-41A POWER9 (architected) 0x4e0202 0xf000005 of:IBM,FW910.00 (VL910_062) hv:phyp pSeries\n[ 2.552872] NIP: c0000000007eef3c LR: c0000000007eef30 CTR: c0000000003d8c90\n[ 2.552885] REGS: c0000000622e73b0 TRAP: 0700 Not tainted (6.12.0-105.debug_vm2.el10.ppc64le+debug)\n[ 2.552899] MSR: 800000000282b033 \u003cSF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE\u003e CR: 24002822 XER: 0000000a\n[ 2.552954] CFAR: c0000000008f03f0 IRQMASK: 0\n[ 2.552954] GPR00: c0000000007eef30 c0000000622e7650 c000000002b1ac00 0000000000000001\n[ 2.552954] GPR04: 0000000000000008 0000000000000000 c0000000007eef30 ffffffffffffffff\n[ 2.552954] GPR08: 00000000ffff00f5 0000000000000001 0000000000000048 0000000000004000\n[ 2.552954] GPR12: 00000003fa440000 c000000017ffa300 c0000000051d9f80 ffffffffffffffdb\n[ 2.552954] GPR16: 0000000000000000 0000000000000008 000000000000000a 60000000000000e0\n[ 2.552954] GPR20: 4080000000000000 c0000000113af038 00007fffcf130000 0000700000000000\n[ 2.552954] GPR24: c000000062a6a000 0000000000000001 8000000062a68000 0000000000000001\n[ 2.552954] GPR28: 000000000000000a c000000062ebc600 0000000000002000 c000000062ebc760\n[ 2.553170] NIP [c0000000007eef3c] free_pud_range+0x8bc/0x8d0\n[ 2.553185] LR [c0000000007eef30] free_pud_range+0x8b0/0x8d0\n[ 2.553199] Call Trace:\n[ 2.553207] [c0000000622e7650] [c0000000007eef30] free_pud_range+0x8b0/0x8d0 (unreliable)\n[ 2.553229] [c0000000622e7750] [c0000000007f40b4] free_pgd_range+0x284/0x3b0\n[ 2.553248] [c0000000622e7800] [c0000000007f4630] free_pgtables+0x450/0x570\n[ 2.553274] [c0000000622e78e0] [c0000000008161c0] exit_mmap+0x250/0x650\n[ 2.553292] [c0000000622e7a30] [c0000000001b95b8] __mmput+0x98/0x290\n[ 2.558344] [c0000000622e7a80] [c0000000001d1018] exit_mm+0x118/0x1b0\n[ 2.558361] [c0000000622e7ac0] [c0000000001d141c] do_exit+0x2ec/0x870\n[ 2.558376] [c0000000622e7b60] [c0000000001d1ca8] do_group_exit+0x88/0x150\n[ 2.558391] [c0000000622e7bb0] [c0000000001d1db8] sys_exit_group+0x48/0x50\n[ 2.558407] [c0000000622e7be0] [c00000000003d810] system_call_exception+0x1e0/0x4c0\n[ 2.558423] [c0000000622e7e50] [c00000000000d05c] system_call_vectored_common+0x15c/0x2ec\n(...)\n[ 2.558892] ---[ end trace 0000000000000000 ]---\n[ 2.559022] BUG: Bad rss-counter state mm:000000002267cc9e type:MM_ANONPAGES val:1\n[ 2.559037] BUG: non-zero pgtables_bytes on freeing mm: -6144\n\nHere the modprobe process ended up with an allocated mm_struct from the\nmm_struct slab that was used before by the debug_vm_pgtable test. That is\nnot a problem, since the mm_stru\n---truncated---",
"id": "GHSA-84v6-6vmq-3v62",
"modified": "2026-05-12T15:31:07Z",
"published": "2025-09-11T18:35:52Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-39776"
},
{
"type": "WEB",
"url": "https://cert-portal.siemens.com/productcert/html/ssa-032379.html"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/47d2a149611b8a94d24add9868c442a4af278658"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/561171db3b3eb759ba3f284dba7a76f4476ade03"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/61a9f2e5c49f05e3ea2c16674540a075a1b4be6f"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/63962ff932ef359925b94be2a88df6b4fd4fed0a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7bf57a0709cd7c9088cea8de023d6f4fbf2518b0"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/dde30854bddfb5d69f30022b53c5955a41088b33"
},
{
"type": "WEB",
"url": "https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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