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

JIRA: https://issues.redhat.com/browse/RHEL-119165
CVE: CVE-2025-39883

commit d613f53
Author: Miaohe Lin <[email protected]>
Date:   Thu Aug 28 10:46:18 2025 +0800

    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-g148743902568 #40
    RIP: 0010:unpoison_memory+0x2f3/0x590
    RSP: 0018:ffffa57fc8787d60 EFLAGS: 00000246
    RAX: 0000000000000037 RBX: 0000000000000009 RCX: ffff9be25fcdc9c8
    RDX: 0000000000000000 RSI: 0000000000000027 RDI: ffff9be25fcdc9c0
    RBP: 0000000000300000 R08: ffffffffb4956f88 R09: 0000000000009ffb
    R10: 0000000000000284 R11: ffffffffb4926fa0 R12: ffffe6b00c000000
    R13: ffff9bdb453dfd00 R14: 0000000000000000 R15: fffffffffffffffe
    FS:  00007f08f04e4740(0000) GS:ffff9be25fcc0000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 0000564787a30410 CR3: 000000010d4e2000 CR4: 00000000000006f0
    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: 0000000000000001
    RAX: ffffffffffffffda RBX: 0000000000000009 RCX: 00007f08f0314887
    RDX: 0000000000000009 RSI: 0000564787a30410 RDI: 0000000000000001
    RBP: 0000564787a30410 R08: 000000000000fefe R09: 000000007fffffff
    R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000009
    R13: 00007f08f041b780 R14: 00007f08f0417600 R15: 00007f08f0416a00
     </TASK>
    Modules linked in: hwpoison_inject
    ---[ end trace 0000000000000000 ]---
    RIP: 0010:unpoison_memory+0x2f3/0x590
    RSP: 0018:ffffa57fc8787d60 EFLAGS: 00000246
    RAX: 0000000000000037 RBX: 0000000000000009 RCX: ffff9be25fcdc9c8
    RDX: 0000000000000000 RSI: 0000000000000027 RDI: ffff9be25fcdc9c0
    RBP: 0000000000300000 R08: ffffffffb4956f88 R09: 0000000000009ffb
    R10: 0000000000000284 R11: ffffffffb4926fa0 R12: ffffe6b00c000000
    R13: ffff9bdb453dfd00 R14: 0000000000000000 R15: fffffffffffffffe
    FS:  00007f08f04e4740(0000) GS:ffff9be25fcc0000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 0000564787a30410 CR3: 000000010d4e2000 CR4: 00000000000006f0
    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.

    Link: https://lkml.kernel.org/r/[email protected]
    Fixes: f1dd2cd ("mm, memory_hotplug: do not associate hotadded memory to zones until online")
    Signed-off-by: Miaohe Lin <[email protected]>
    Suggested-by: David Hildenbrand <[email protected]>
    Acked-by: David Hildenbrand <[email protected]>
    Cc: Naoya Horiguchi <[email protected]>
    Cc: <[email protected]>
    Signed-off-by: Andrew Morton <[email protected]>

Signed-off-by: CKI Backport Bot <[email protected]>

Author: CKI Backport Bot

mm/memory-failure.c

@@ -2555,10 +2555,9 @@ int unpoison_memory(unsigned long pfn)
 	static DEFINE_RATELIMIT_STATE(unpoison_rs, DEFAULT_RATELIMIT_INTERVAL,
 					DEFAULT_RATELIMIT_BURST);
 
-	if (!pfn_valid(pfn))
-		return -ENXIO;
-
-	p = pfn_to_page(pfn);
+	p = pfn_to_online_page(pfn);
+	if (!p)
+		return -EIO;
 	folio = page_folio(p);
 
 	mutex_lock(&mf_mutex);