CVE-2025-21860

Published Mar 12, 2025

Last updated a year ago

Overview

Description
In the Linux kernel, the following vulnerability has been resolved: mm/zswap: fix inconsistency when zswap_store_page() fails Commit b7c0ccdfbafd ("mm: zswap: support large folios in zswap_store()") skips charging any zswap entries when it failed to zswap the entire folio. However, when some base pages are zswapped but it failed to zswap the entire folio, the zswap operation is rolled back. When freeing zswap entries for those pages, zswap_entry_free() uncharges the zswap entries that were not previously charged, causing zswap charging to become inconsistent. This inconsistency triggers two warnings with following steps: # On a machine with 64GiB of RAM and 36GiB of zswap $ stress-ng --bigheap 2 # wait until the OOM-killer kills stress-ng $ sudo reboot The two warnings are: in mm/memcontrol.c:163, function obj_cgroup_release(): WARN_ON_ONCE(nr_bytes & (PAGE_SIZE - 1)); in mm/page_counter.c:60, function page_counter_cancel(): if (WARN_ONCE(new < 0, "page_counter underflow: %ld nr_pages=%lu\n", new, nr_pages)) zswap_stored_pages also becomes inconsistent in the same way. As suggested by Kanchana, increment zswap_stored_pages and charge zswap entries within zswap_store_page() when it succeeds. This way, zswap_entry_free() will decrement the counter and uncharge the entries when it failed to zswap the entire folio. While this could potentially be optimized by batching objcg charging and incrementing the counter, let's focus on fixing the bug this time and leave the optimization for later after some evaluation. After resolving the inconsistency, the warnings disappear. [42.hyeyoo@gmail.com: refactor zswap_store_page()]
Source
416baaa9-dc9f-4396-8d5f-8c081fb06d67
NVD status
Modified
Products
linux_kernel

Risk scores

CVSS 3.1

Type
Primary
Base score
3.3
Impact score
1.4
Exploitability score
1.8
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
Severity
LOW

Weaknesses

nvd@nist.gov
NVD-CWE-noinfo

Social media

Hype score
Not currently trending

Configurations

  1. In the Linux kernel, the following vulnerability has been resolved: coresight: tmc-etr: Fix race condition between sysfs and perf mode When trying to run perf and sysfs mode simultaneously, the WARN_ON() in tmc_etr_enable_hw() is triggered sometimes: WARNING: CPU: 42 PID: 3911571 at drivers/hwtracing/coresight/coresight-tmc-etr.c:1060 tmc_etr_enable_hw+0xc0/0xd8 [coresight_tmc] [..snip..] Call trace: tmc_etr_enable_hw+0xc0/0xd8 [coresight_tmc] (P) tmc_enable_etr_sink+0x11c/0x250 [coresight_tmc] (L) tmc_enable_etr_sink+0x11c/0x250 [coresight_tmc] coresight_enable_path+0x1c8/0x218 [coresight] coresight_enable_sysfs+0xa4/0x228 [coresight] enable_source_store+0x58/0xa8 [coresight] dev_attr_store+0x20/0x40 sysfs_kf_write+0x4c/0x68 kernfs_fop_write_iter+0x120/0x1b8 vfs_write+0x2c8/0x388 ksys_write+0x74/0x108 __arm64_sys_write+0x24/0x38 el0_svc_common.constprop.0+0x64/0x148 do_el0_svc+0x24/0x38 el0_svc+0x3c/0x130 el0t_64_sync_handler+0xc8/0xd0 el0t_64_sync+0x1ac/0x1b0 ---[ end trace 0000000000000000 ]--- Since the enablement of sysfs mode is separeted into two critical regions, one for sysfs buffer allocation and another for hardware enablement, it's possible to race with the perf mode. Fix this by double check whether the perf mode's been used before enabling the hardware in sysfs mode. mode: [sysfs mode] [perf mode] tmc_etr_get_sysfs_buffer() spin_lock(&drvdata->spinlock) [sysfs buffer allocation] spin_unlock(&drvdata->spinlock) spin_lock(&drvdata->spinlock) tmc_etr_enable_hw() drvdata->etr_buf = etr_perf->etr_buf spin_unlock(&drvdata->spinlock) spin_lock(&drvdata->spinlock) tmc_etr_enable_hw() WARN_ON(drvdata->etr_buf) // WARN sicne etr_buf initialized at the perf side spin_unlock(&drvdata->spinlock) With this fix, we retain the check for CS_MODE_PERF in get_etr_sysfs_buf. This ensures we verify whether the perf mode's already running before we actually allocate the buffer. Then we can save the time of allocating/freeing the sysfs buffer if race with the perf mode.CVE-2026-46272