From: "David Hildenbrand (Arm)" <david@kernel.org>
To: "Mike Rapoport (Microsoft)" <rppt@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Alexander Potapenko <glider@google.com>,
Marco Elver <elver@google.com>,
"Rafael J. Wysocki" <rafael@kernel.org>
Cc: Dmitry Vyukov <dvyukov@google.com>, Len Brown <lenb@kernel.org>,
Pavel Machek <pavel@kernel.org>,
kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, linux-pm@vger.kernel.org
Subject: Re: [PATCH 5/5] hibernation: make hibernation unavailable when debug_pagealloc is on
Date: Wed, 23 Sep 2026 12:24:41 +0200 [thread overview]
Message-ID: <5f950806-3e76-4a16-9511-a23719125f4b@kernel.org> (raw)
In-Reply-To: <20260917-hibernation-v1-5-7f7dfae3dbe0@kernel.org>
On 9/17/26 08:07, Mike Rapoport (Microsoft) wrote:
> Back in 2008 when commit 8a235efad548a ("Hibernation: Handle
> DEBUG_PAGEALLOC on x86") enabled coexistence of hibernation and
> DEBUG_PAGEALLOC, the world was simpler, the combination was only supported
> on x86 and a non-present page in the direct map meant that the page was
> free and debug_pagealloc removed its mapping.
>
> Nowadays there are more architectures with inconsistent views of how the
> direct map should be managed, there are more debug mechanisms in MM that
> can either drop a page from the direct map (e.g. KFENCE) or require that a
> page must be mapped immediately after resume (e.g. init_on_free).
>
> The latter constraint is particularly nasty, because enabling
> debug_pagealloc and PAGE_POISON at the same time simply breaks resume:
>
> BUG: unable to handle page fault for address: ffff888000100000
> #PF: supervisor write access in kernel mode
> #PF: error_code(0x0002) - not-present page
> PGD 4f0c067 P4D 4f0c067 PUD 4f0d067 PMD 4f0e067 PTE 800fffffffeff020
> Oops: Oops: 0002 [#1] SMP DEBUG_PAGEALLOC NOPTI
> CPU: 0 UID: 0 PID: 477 Comm: bash Not tainted 7.3.0-rc3-00090-g4a613f1d9124 #1 PREEMPT(full)
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.17.0-debian-1.17.0-1 04/01/2014
> RIP: 0010:__kernel_poison_pages+0x45/0x70
> Code: 89 fa 48 c1 e6 06 48 01 fe 48 89 d1 48 2b 0d 9a ed 87 01 48 83 c2 40 48 c1 f9 06 48 c1 e1 0c 48 03 0d 97 ed 87 01 48 8d 79 08 <48> 89 01 48 83 e7 f8 48 89 81 f8 0f 00 00 48 29 f9 81 c1 00 10 00
> RSP: 0018:ffffc900017dfd78 EFLAGS: 00010086
> RAX: aaaaaaaaaaaaaaaa RBX: 0000000000000000 RCX: ffff888000100000
> RDX: ffffea0000004040 RSI: ffffea0000004040 RDI: ffff888000100008
> RBP: 0000000000000000 R08: ffff888130fcada0 R09: 00000000723e0de4
> R10: 0000000096ad9215 R11: 00000000db907bcf R12: 0000000000000005
> R13: 0000000000000005 R14: 0000000000000000 R15: 0000000000000000
> FS: 00007f8f2243e780(0000) GS:ffff8882e8e13000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffff888000100000 CR3: 0000000140679000 CR4: 0000000000750ef0
> PKRU: 55555554
> Call Trace:
> <TASK>
> clear_or_poison_free_pages+0xd1/0xe0
> hibernation_snapshot+0x548/0x5a0
> hibernate.cold+0xcb/0x321
> state_store+0xc3/0xd0
> kernfs_fop_write_iter+0x163/0x240
> vfs_write+0x21f/0x550
> ksys_write+0x70/0xf0
> do_syscall_64+0xb1/0x590
> ? __irq_exit_rcu+0x40/0x110
> entry_SYSCALL_64_after_hwframe+0x76/0x7e
> RIP: 0033:0x7f8f224d0687
> Code: 48 89 fa 4c 89 df e8 58 b3 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
> RSP: 002b:00007ffe7bbe0910 EFLAGS: 00000202 ORIG_RAX: 0000000000000001
> RAX: ffffffffffffffda RBX: 00007f8f2243e780 RCX: 00007f8f224d0687
> RDX: 0000000000000005 RSI: 000055e3e53135d0 RDI: 0000000000000001
> RBP: 000055e3e53135d0 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000005
> R13: 00007f8f226295c0 R14: 00007f8f22626e80 R15: 0000000000000000
> </TASK>
> Modules linked in:
> CR2: ffff888000100000
>
> It's possible to build a complex infrastructure involving a new page flag
> and/or page_type to allow robust hibernation and restore with
> debug_pagealloc enabled.
>
> This infrastructure requires a proper detection whether it is safe to
> temporarily remap a page to include it in the hibernation snapshot because
> relying on kernel_page_present() is too permissive and may include pages
> that were deliberately removed from the direct map for security reasons.
>
> This complexity does not seem justified to deal with an esoteric use case
> of hibernating a system that runs with debug_pagealloc enabled.
>
> Make hibernation unavailable when debug_pagealloc is enabled and simplify
> hibernate_{map,unmap}_page() that don't need to deal with debug_pagealloc
> anymore.
>
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
--
Cheers,
David
next prev parent reply other threads:[~2026-09-23 10:24 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-17 6:07 [PATCH 0/5] hibernation: make safe_copy_page more robust and remove debug_pagealloc support Mike Rapoport (Microsoft)
2026-09-17 6:07 ` [PATCH 1/5] hibernation: make swsusp_page helpers static Mike Rapoport (Microsoft)
2026-09-23 10:08 ` David Hildenbrand (Arm)
2026-09-17 6:07 ` [PATCH 2/5] hibernation: ensure secretmem pages don't reach a snapshot Mike Rapoport (Microsoft)
2026-09-23 10:10 ` David Hildenbrand (Arm)
2026-09-23 15:38 ` Mike Rapoport
2026-09-17 6:07 ` [PATCH 3/5] hibernate: handle potential errors in hibernate_{map,unmap}_page() Mike Rapoport (Microsoft)
2026-09-23 10:13 ` David Hildenbrand (Arm)
2026-09-23 15:42 ` Mike Rapoport
2026-09-17 6:07 ` [PATCH 4/5] hibernation, KFENCE: explicitly map/unmap KFENCE pages Mike Rapoport (Microsoft)
2026-09-23 10:31 ` David Hildenbrand (Arm)
2026-09-23 15:49 ` Mike Rapoport
2026-09-17 6:07 ` [PATCH 5/5] hibernation: make hibernation unavailable when debug_pagealloc is on Mike Rapoport (Microsoft)
2026-09-23 10:24 ` David Hildenbrand (Arm) [this message]
2026-09-23 9:26 ` [PATCH 0/5] hibernation: make safe_copy_page more robust and remove debug_pagealloc support Mike Rapoport
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