In the Linux kernel, the following vulnerability has been resolved:
mm: fix crashes from deferred split racing folio migration
Even on 6.10-rc6, I've been seeing elusive "Bad page state"s (often on
flags when freeing, yet the flags shown are not bad: PG_locked had been
set and cleared??), and VM_BUG_ON_PAGE(page_ref_count(page) == 0)s from
deferred_split_scan()'s folio_put(), and a variety of other BUG and WARN
symptoms implying double free by deferred split and large folio migration.
6.7 commit 9bcef5973e31 ("mm: memcg: fix split queue list crash when large
folio migration") was right to fix the memcg-dependent locking broken in
85ce2c517ade ("memcontrol: only transfer the memcg data for migration"),
but missed a subtlety of deferred_split_scan(): it moves folios to its own
local list to work on them without split_queue_lock, during which time
folio->_deferred_list is not empty, but even the "right" lock does nothing
to secure the folio and the list it is on.
Fortunately, deferred_split_scan() is careful to use folio_try_get(): so
folio_migrate_mapping() can avoid the race by folio_undo_large_rmappable()
while the old folio's reference count is temporarily frozen to 0 - adding
such a freeze in the !mapping case too (originally, folio lock and
unmapping and no swap cache left an anon folio unreachable, so no freezing
was needed there: but the deferred split queue offers a way to reach it).
Metrics
Affected Vendors & Products
References
History
Wed, 11 Sep 2024 13:30:00 +0000
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Mon, 12 Aug 2024 10:30:00 +0000
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Thu, 08 Aug 2024 21:30:00 +0000
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Thu, 08 Aug 2024 15:15:00 +0000
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Linux
Linux linux Kernel |
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Weaknesses | CWE-415 | |
CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
Vendors & Products |
Linux
Linux linux Kernel |
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Metrics |
cvssV3_1
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Wed, 07 Aug 2024 15:30:00 +0000
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Description | In the Linux kernel, the following vulnerability has been resolved: mm: fix crashes from deferred split racing folio migration Even on 6.10-rc6, I've been seeing elusive "Bad page state"s (often on flags when freeing, yet the flags shown are not bad: PG_locked had been set and cleared??), and VM_BUG_ON_PAGE(page_ref_count(page) == 0)s from deferred_split_scan()'s folio_put(), and a variety of other BUG and WARN symptoms implying double free by deferred split and large folio migration. 6.7 commit 9bcef5973e31 ("mm: memcg: fix split queue list crash when large folio migration") was right to fix the memcg-dependent locking broken in 85ce2c517ade ("memcontrol: only transfer the memcg data for migration"), but missed a subtlety of deferred_split_scan(): it moves folios to its own local list to work on them without split_queue_lock, during which time folio->_deferred_list is not empty, but even the "right" lock does nothing to secure the folio and the list it is on. Fortunately, deferred_split_scan() is careful to use folio_try_get(): so folio_migrate_mapping() can avoid the race by folio_undo_large_rmappable() while the old folio's reference count is temporarily frozen to 0 - adding such a freeze in the !mapping case too (originally, folio lock and unmapping and no swap cache left an anon folio unreachable, so no freezing was needed there: but the deferred split queue offers a way to reach it). | |
Title | mm: fix crashes from deferred split racing folio migration | |
References |
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MITRE
Status: PUBLISHED
Assigner: Linux
Published: 2024-08-07T15:14:24.467Z
Updated: 2024-12-19T09:14:32.963Z
Reserved: 2024-07-30T07:40:12.252Z
Link: CVE-2024-42234
Vulnrichment
Updated: 2024-09-11T12:42:24.305Z
NVD
Status : Analyzed
Published: 2024-08-07T16:15:46.390
Modified: 2024-08-08T14:55:29.913
Link: CVE-2024-42234
Redhat