CVE-2026-97945— x86/mm: Fix user-space data loss with MADV_FREE and THP
Quick assessment
Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
在 Linux 内核中，已修复以下漏洞： x86/mm：修复 MADV_FREE 与 THP（大页面）导致的用户空间数据丢失问题 一些使用 Polars（一个数据分析库）的用户因该漏洞在生产环境中丢失了数据。该问题的触发条件似乎是恰好同时具备大页面、MADV_FREE 标志以及较重的页面回收压力。 函数在修改页面目录条目（PMD）时，会使用 掩码对旧值进行屏蔽，从而静默地丢弃了硬件脏位（dirty bit）。随后调用的 本应在写保护时将 转换为 ，但由于脏位已被提前剥离，没有数据可供转换。 相比之下， 在掩码中保留
Possible ATT&CK Techniques 1 AI
T1564.004 · NTFS File AttributesAffected Version Matrix 12
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| Linux | Linux | bb3aadf7d446aaf22c725b274e2c194ac5cb2111< b5dec6dfb593d81fec15ba43c4fe5d58f10a49a2 |
affected |
bb3aadf7d446aaf22c725b274e2c194ac5cb2111< e4d569fe2f436a9b58c048fefabf56eab68c1b7e |
affected | ||
bb3aadf7d446aaf22c725b274e2c194ac5cb2111< 55ddbc2ca6d5db64d44c3fb8f8705b4d39eb30b7 |
affected | ||
bb3aadf7d446aaf22c725b274e2c194ac5cb2111< a5ad97cbcfcec31430268441c10eedde73200177 |
affected | ||
bb3aadf7d446aaf22c725b274e2c194ac5cb2111< f7491d7c81db0e7c304a7bd757a76d2fbeaff80e |
affected | ||
6.6 |
affected | ||
< 6.6 |
unaffected | ||
6.6.158≤ 6.6.* |
unaffected | ||
| … +4 more rows | |||
Get alerts for future matching vulnerabilities
Log in to subscribe
I. Basic Information for CVE-2026-97945
Vulnerability Information
Have questions about the vulnerability? See if Shenlong's analysis helps!
View Shenlong Deep Dive ↗
Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.
Vulnerability Title
x86/mm: Fix user-space data loss with MADV_FREE and THP
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved:
x86/mm: Fix user-space data loss with MADV_FREE and THP
Some of users of Polars (a data analytics library) have lost production
data from this bug. They seem to have just the right combination of
huge pages, MADV_FREE and heavy reclaim pressure.
pmd_modify() masks the old value with (_HPAGE_CHG_MASK & ~_PAGE_DIRTY),
silently discarding the hardware dirty bit. The subsequent
pmd_mksaveddirty() call is supposed to transfer _PAGE_DIRTY into
_PAGE_SAVED_DIRTY when write-protecting, but the dirty bit was already
stripped from the value, so there is nothing left to transfer.
Contrast with pte_modify(), which keeps _PAGE_DIRTY_BITS in its mask,
and pud_modify(), which keeps _HPAGE_CHG_MASK untouched: pmd_modify()
is the odd one out. Any pmd_modify() on a writable, dirty PMD loses
the dirty state.
One visible consequence is data loss with MADV_FREE on PMD-mapped THP:
memset(buf, 0x5A, size); // PMD-mapped THP, PMD dirty
madvise(buf, size, MADV_FREE); // PMD cleaned but left writable,
// folio marked lazyfree
memset(buf, 0x5A, size); // hardware sets _PAGE_DIRTY again
mprotect(buf, size, PROT_READ); // pmd_modify() drops the dirty bit
mprotect(buf, size, PROT_READ|PROT_WRITE);
// ... memory pressure ...
Reclaim (e.g. under memcg pressure) then finds the lazyfree folio with
no dirty bit set anywhere and frees it in
__discard_anon_folio_pmd_locked(), even though the data was rewritten
after MADV_FREE; subsequent reads fault in fresh zero pages. NUMA
hinting alone can trigger the same loss, as do_huge_pmd_numa_page()
restores the PMD through pmd_modify() as well.
PMD-mapped file THPs are affected too: mprotect()/NUMA hinting dropping
the dirty bit means rewritten data is never written back.
Fix it by keeping _PAGE_DIRTY in the preserved mask, exactly like
pte_modify() and pud_modify() do. The existing
pmd_mksaveddirty()/pmd_clear_saveddirty() pair then performs the
hardware-dirty <-> saved-dirty transition based on the write bit,
preserving the shadow-stack encoding rules.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Affected Products
II. Public POCs for CVE-2026-97945
| # | POC Description | Source Link | Shenlong Link |
|---|
AI-Generated POC
Premium
No public POC found.
Login to generate AI POCIII. Intelligence Information for CVE-2026-97945
请登录查看更多情报信息。
Patches & Fixes for CVE-2026-97945 (4)
Other References for CVE-2026-97945 (1)
Same Patch Batch · Linux · 2026-09-25 · 372 CVEs total
| CVE-2026-100075 | 9.8 CRITICAL | RDMA/srpt: Fix srpt_alloc_rw_ctxs() unwind counters |
| CVE-2026-97555 | 8.8 HIGH | smb: client: fix heap overflow in DACL owner/group rewrite |
| CVE-2026-97957 | 8.8 HIGH | net: hinic: fix mailbox segment buffer overflow |
| CVE-2026-97527 | 8.8 HIGH | scsi: qla2xxx: Serialize NVMe unsol ctx list with a per-fcport lock |
| CVE-2026-97528 | 8.8 HIGH | scsi: qla2xxx: Unlink NVMe unsol ctx before freeing on LS reject error |
| CVE-2026-98115 | 8.8 HIGH | ksmbd: safely drain sessions during logoff |
| CVE-2026-97525 | 8.2 HIGH | x86/mm/pat: Allocate split page tables as kernel page tables |
| CVE-2026-98069 | 8.1 HIGH | net/rds: acquire the fastpath locks in rds_conn_shutdown() |
| CVE-2026-97573 | 8.1 HIGH | bnxt_en: Handle buffer allocation failure in bnxt_rx_ring_reset() |
| CVE-2026-97570 | 8.1 HIGH | bnxt_en: Bound SW TPA IDs to prevent crashes |
| CVE-2026-98130 | 8.1 HIGH | sctp: fix a TOCTOU race in SCTP_CMD_TIMER_START |
| CVE-2026-98070 | 8.1 HIGH | net/rds: acquire RDS_IN_XMIT in rds_tcp_reset_callbacks() |
| CVE-2026-97941 | 7.8 HIGH | mm/slab: take n->list_lock in __slab_try_return_freelist() to avoid race |
| CVE-2026-97575 | 7.8 HIGH | media: v4l2-ctrls: validate AV1 tile counts |
| CVE-2026-97576 | 7.8 HIGH | media: v4l2-ctrls: validate HEVC tile counts |
| CVE-2026-98112 | 7.8 HIGH | ksmbd: fix listener task lifetime on netdev events |
| CVE-2026-98002 | 7.8 HIGH | iommu/amd: Fix ineffective error check in nested domain allocation |
| CVE-2026-97937 | 7.8 HIGH | ftrace: fork: Initialize function graph state before copy_exec_state() |
| CVE-2026-97580 | 7.8 HIGH | media: rkvdec: bound HEVC tile loops and PPS id to the array capacity |
| CVE-2026-97940 | 7.8 HIGH | ipv6: fix fib6 walker UAF on seq stop |
Showing top 20 of 372 CVEs. View all on vendor page → →
IV. Related Vulnerabilities
Same product: Linux
-
CVE-2026-98384
bpf: Fix out-of-bounds read of sk_protocol in bpf_sock_destr -
CVE-2026-98383
bpf: Disallow bpf_skb_pull_data() for LWT_SEG6LOCAL -
CVE-2026-98382
bpf: Reject dev-bound-only programs on other devices -
CVE-2026-98381
veth: manage XDP program pointers during channel resize -
CVE-2026-98380
net/sched: reject IDR error pointers when deleting actions
Same vendor: Linux
-
CVE-2026-98384
bpf: Fix out-of-bounds read of sk_protocol in bpf_sock_destr -
CVE-2026-98383
bpf: Disallow bpf_skb_pull_data() for LWT_SEG6LOCAL -
CVE-2026-98382
bpf: Reject dev-bound-only programs on other devices -
CVE-2026-98381
veth: manage XDP program pointers during channel resize -
CVE-2026-98380
net/sched: reject IDR error pointers when deleting actions
V. Comments for CVE-2026-97945
No comments yet