vulnerability
Amazon Linux 2023: CVE-2025-38338: Important priority package update for kernel6.12
| Severity | CVSS | Published | Added | Modified |
|---|---|---|---|---|
| 5 | (AV:L/AC:L/Au:S/C:N/I:N/A:C) | Jul 10, 2025 | Sep 9, 2025 | Dec 4, 2025 |
Severity
5
CVSS
(AV:L/AC:L/Au:S/C:N/I:N/A:C)
Published
Jul 10, 2025
Added
Sep 9, 2025
Modified
Dec 4, 2025
Description
In the Linux kernel, the following vulnerability has been resolved:
fs/nfs/read: fix double-unlock bug in nfs_return_empty_folio()
Sometimes, when a file was read while it was being truncated by
another NFS client, the kernel could deadlock because folio_unlock()
was called twice, and the second call would XOR back the `PG_locked`
flag.
Most of the time (depending on the timing of the truncation), nobody
notices the problem because folio_unlock() gets called three times,
which flips `PG_locked` back off:
1. vfs_read, nfs_read_folio, ... nfs_read_add_folio,
nfs_return_empty_folio
2. vfs_read, nfs_read_folio, ... netfs_read_collection,
netfs_unlock_abandoned_read_pages
3. vfs_read, ... nfs_do_read_folio, nfs_read_add_folio,
nfs_return_empty_folio
The problem is that nfs_read_add_folio() is not supposed to unlock the
folio if fscache is enabled, and a nfs_netfs_folio_unlock() check is
missing in nfs_return_empty_folio().
Rarely this leads to a warning in netfs_read_collection():
------------[ cut here ]------------
R=0000031c: folio 10 is not locked
WARNING: CPU: 0 PID: 29 at fs/netfs/read_collect.c:133 netfs_read_collection+0x7c0/0xf00
[...]
Workqueue: events_unbound netfs_read_collection_worker
RIP: 0010:netfs_read_collection+0x7c0/0xf00
[...]
Call Trace:
<TASK>
netfs_read_collection_worker+0x67/0x80
process_one_work+0x12e/0x2c0
worker_thread+0x295/0x3a0
Most of the time, however, processes just get stuck forever in
folio_wait_bit_common(), waiting for `PG_locked` to disappear, which
never happens because nobody is really holding the folio lock.
fs/nfs/read: fix double-unlock bug in nfs_return_empty_folio()
Sometimes, when a file was read while it was being truncated by
another NFS client, the kernel could deadlock because folio_unlock()
was called twice, and the second call would XOR back the `PG_locked`
flag.
Most of the time (depending on the timing of the truncation), nobody
notices the problem because folio_unlock() gets called three times,
which flips `PG_locked` back off:
1. vfs_read, nfs_read_folio, ... nfs_read_add_folio,
nfs_return_empty_folio
2. vfs_read, nfs_read_folio, ... netfs_read_collection,
netfs_unlock_abandoned_read_pages
3. vfs_read, ... nfs_do_read_folio, nfs_read_add_folio,
nfs_return_empty_folio
The problem is that nfs_read_add_folio() is not supposed to unlock the
folio if fscache is enabled, and a nfs_netfs_folio_unlock() check is
missing in nfs_return_empty_folio().
Rarely this leads to a warning in netfs_read_collection():
------------[ cut here ]------------
R=0000031c: folio 10 is not locked
WARNING: CPU: 0 PID: 29 at fs/netfs/read_collect.c:133 netfs_read_collection+0x7c0/0xf00
[...]
Workqueue: events_unbound netfs_read_collection_worker
RIP: 0010:netfs_read_collection+0x7c0/0xf00
[...]
Call Trace:
<TASK>
netfs_read_collection_worker+0x67/0x80
process_one_work+0x12e/0x2c0
worker_thread+0x295/0x3a0
Most of the time, however, processes just get stuck forever in
folio_wait_bit_common(), waiting for `PG_locked` to disappear, which
never happens because nobody is really holding the folio lock.
Solutions
amazon-linux-2023-upgrade-bpftoolamazon-linux-2023-upgrade-bpftool-debuginfoamazon-linux-2023-upgrade-kernel6-12amazon-linux-2023-upgrade-kernel6-12-debuginfoamazon-linux-2023-upgrade-kernel6-12-debuginfo-common-aarch64amazon-linux-2023-upgrade-kernel6-12-debuginfo-common-x86-64amazon-linux-2023-upgrade-kernel6-12-modules-extraamazon-linux-2023-upgrade-kernel-develamazon-linux-2023-upgrade-kernel-headersamazon-linux-2023-upgrade-kernel-libbpfamazon-linux-2023-upgrade-kernel-libbpf-debuginfoamazon-linux-2023-upgrade-kernel-libbpf-develamazon-linux-2023-upgrade-kernel-libbpf-staticamazon-linux-2023-upgrade-kernel-livepatch-6-12-35-55-103amazon-linux-2023-upgrade-kernel-modules-extra-commonamazon-linux-2023-upgrade-kernel-toolsamazon-linux-2023-upgrade-kernel-tools-debuginfoamazon-linux-2023-upgrade-kernel-tools-develamazon-linux-2023-upgrade-perf6-12amazon-linux-2023-upgrade-perf6-12-debuginfoamazon-linux-2023-upgrade-python3-perf6-12amazon-linux-2023-upgrade-python3-perf6-12-debuginfo
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