CVE: CVE-2025-39883
Published: 2025-09-23
Description: In the Linux kernel, the following vulnerability has been resolved:

mm/memory-failure: fix VM_BUG_ON_PAGE(PagePoisoned(page)) when unpoison memory

When I did memory failure tests, below panic occurs:

page dumped because: VM_BUG_ON_PAGE(PagePoisoned(page))
kernel BUG at include/linux/page-flags.h:616!
Oops: invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
CPU: 3 PID: 720 Comm: bash Not tainted 6.10.0-rc1-00195-g[PII_REDACTED]8 #40
RIP: 0010:unpoison_memory+0x2f3/0x590
RSP: 0018:ffffa57fc8787d60 EFLAGS: 00000246
RAX: [PII_REDACTED] RBX: [PII_REDACTED] RCX: ffff9be25fcdc9c8
RDX: [PII_REDACTED] RSI: [PII_REDACTED] RDI: ffff9be25fcdc9c0
RBP: [PII_REDACTED] R08: ffffffffb4956f88 R09:[PII_REDACTED]009ffb
R10: [PII_REDACTED] R11: ffffffffb4926fa0 R12: ffffe6b00c000000
R13: ffff9bdb453dfd00 R14: [PII_REDACTED] R15: fffffffffffffffe
FS:  00007f08f04e4740(0000) GS:ffff9be25fcc0000(0000) knlGS:[PII_REDACTED]
CS:  0010 DS: 0000 ES: 0000 CR0: [PII_REDACTED]
CR2:[PII_REDACTED]a30410 CR3: 000000010d4e2000 CR4:[PII_REDACTED]0006f0
Call Trace:
 <TASK>
 unpoison_memory+0x2f3/0x590
 simple_attr_write_xsigned.constprop.0.isra.0+0xb3/0x110
 debugfs_attr_write+0x42/0x60
 full_proxy_write+0x5b/0x80
 vfs_write+0xd5/0x540
 ksys_write+0x64/0xe0
 do_syscall_64+0xb9/0x1d0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f08f0314887
RSP: 002b:00007ffece710078 EFLAGS: 00000246 ORIG_RAX: [PII_REDACTED]
RAX: ffffffffffffffda RBX: [PII_REDACTED] RCX: 00007f08f0314887
RDX: [PII_REDACTED] RSI:[PII_REDACTED]a30410 RDI: [PII_REDACTED]
RBP:[PII_REDACTED]a30410 R08:[PII_REDACTED]00fefe R09: 000000007fffffff
R10: [PII_REDACTED] R11: [PII_REDACTED] R12: [PII_REDACTED]
R13: 00007f08f041b780 R14: 00007f08f0417600 R15: 00007f08f0416a00
 </TASK>
Modules linked in: hwpoison_inject
---[ end trace [PII_REDACTED] ]---
RIP: 0010:unpoison_memory+0x2f3/0x590
RSP: 0018:ffffa57fc8787d60 EFLAGS: 00000246
RAX: [PII_REDACTED] RBX: [PII_REDACTED] RCX: ffff9be25fcdc9c8
RDX: [PII_REDACTED] RSI: [PII_REDACTED] RDI: ffff9be25fcdc9c0
RBP: [PII_REDACTED] R08: ffffffffb4956f88 R09:[PII_REDACTED]009ffb
R10: [PII_REDACTED] R11: ffffffffb4926fa0 R12: ffffe6b00c000000
R13: ffff9bdb453dfd00 R14: [PII_REDACTED] R15: fffffffffffffffe
FS:  00007f08f04e4740(0000) GS:ffff9be25fcc0000(0000) knlGS:[PII_REDACTED]
CS:  0010 DS: 0000 ES: 0000 CR0: [PII_REDACTED]
CR2:[PII_REDACTED]a30410 CR3: 000000010d4e2000 CR4:[PII_REDACTED]0006f0
Kernel panic - not syncing: Fatal exception
Kernel Offset: 0x31c00000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
---[ end Kernel panic - not syncing: Fatal exception ]---

The root cause is that unpoison_memory() tries to check the PG_HWPoison
flags of an uninitialized page.  So VM_BUG_ON_PAGE(PagePoisoned(page)) is
triggered.  This can be reproduced by below steps:

1.Offline memory block:

 echo offline > /sys/devices/system/memory/memory12/state

2.Get offlined memory pfn:

 page-types -b n -rlN

3.Write pfn to unpoison-pfn

 echo <pfn> > /sys/kernel/debug/hwpoison/unpoison-pfn

This scenario can be identified by pfn_to_online_page() returning NULL. 
And ZONE_DEVICE pages are never expected, so we can simply fail if
pfn_to_online_page() == NULL to fix the bug.
CVSS Score: 7.1 (HIGH)
CWE: CWE-125
References: https://git.kernel.org/stable/c/3d278e89c2ea62b1aaa4b0d8a9766a35b3a3164a; https://git.kernel.org/stable/c/63a327a2375a8ce7a47dec5aaa4d8a9ae0a00b96; https://git.kernel.org/stable/c/7618fd443aa4cfa553a64cacf[PII_REDACTED]ee7b0