On 20.12.24 03:35, Miaohe Lin wrote:
On 2024/12/19 20:18, David Hildenbrand wrote:
On 19.12.24 12:52, Miaohe Lin wrote:
When I did memory failure tests recently, 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
Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
---
v2: Use pfn_to_online_page per David. Thanks.
---
mm/memory-failure.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index a7b8ccd29b6f..02be0596ce67 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -2556,10 +2556,18 @@ 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_online_page(pfn);
+ if (!p) {
+ struct dev_pagemap *pgmap;
- p = pfn_to_page(pfn);
+ if (!pfn_valid(pfn))
+ return -ENXIO;
+ pgmap = get_dev_pagemap(pfn, NULL);
+ if (!pgmap)
+ return -ENXIO;
+ put_dev_pagemap(pgmap);
+ p = pfn_to_page(pfn);
+ }
Hm, I wonder if we can do anything reasonable with ZONE_DEVICE pages here?
All I can see in unpoison_memory() is folio_test_clear_hwpoison() for ZONE_DEVICE pages.
IIRC, it can only be triggered via debugfs in special kernel configs. So
chances are this was never ever actually run against a ZONE_DEVICE page.
CCing Dan, maybe he knows if this interface used to do something reasonable with ZONE_DEVICE pages.
Also, I'm not sure about using the page after doing the put_dev_pagemap(). Likely we would have to do that at the before exiting from this function.
IMHO, the page can be used after doing put_dev_pagemap(). The page should still be
available while it has HWPoison set.
1) Why do you think it can be used afterwards? :)
2) At that point in time you don't even know yet if the page is
HWPoisoned! That check is performed later
3) From GUP code, I recall that we must keep the pagemap referenced
until we grabbed a page/folio reference.
Or are you worrying about memory offline? That
might not be the scope of this problem. But I might be miss something.
I suspect unpoison_memory() doesn't do with ZONE_DEVICE pages what it
should be doing. Maybe I'm wrong, it would be great to get feedback from
Dan.
--
Cheers,
David / dhildenb
