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CVE Record

CVE-2025-40012: net/smc: fix warning in smc_rx_splice() when calling get_page()

In the Linux kernel, the following vulnerability has been resolved: net/smc: fix warning in smc_rx_splice() when calling get_page() smc_lo_register_dmb() allocates DMB buffers with kzalloc(), which are later passed to get_page() in smc_rx_splice(). Since kmalloc memory is not page-backed, this triggers WARN_ON_ONCE() in get_page() and prevents holding a refcount on the buffer. This can lead to use-after-free if the memory is released before splice_to_pipe() completes. Use folio_alloc() instead, ensuring DMBs are page-backed and safe for get_page(). WARNING: CPU: 18 PID: 12152 at ./include/linux/mm.h:1330 smc_rx_splice+0xaf8/0xe20 [smc] CPU: 18 UID: 0 PID: 12152 Comm: smcapp Kdump: loaded Not tainted 6.17.0-rc3-11705-g9cf4672ecfee #10 NONE Hardware name: IBM 3931 A01 704 (z/VM 7.4.0) Krnl PSW : 0704e00180000000 000793161032696c (smc_rx_splice+0xafc/0xe20 [smc]) R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:2 PM:0 RI:0 EA:3 Krnl GPRS: 0000000000000000 001cee80007d3001 00077400000000f8 0000000000000005 0000000000000001 001cee80007d3006 0007740000001000 001c000000000000 000000009b0c99e0 0000000000001000 001c0000000000f8 001c000000000000 000003ffcc6f7c88 0007740003e98000 0007931600000005 000792969b2ff7b8 Krnl Code: 0007931610326960: af000000 mc 0,0 0007931610326964: a7f4ff43 brc 15,00079316103267ea #0007931610326968: af000000 mc 0,0 >000793161032696c: a7f4ff3f brc 15,00079316103267ea 0007931610326970: e320f1000004 lg %r2,256(%r15) 0007931610326976: c0e53fd1b5f5 brasl %r14,000793168fd5d560 000793161032697c: a7f4fbb5 brc 15,00079316103260e6 0007931610326980: b904002b lgr %r2,%r11 Call Trace: smc_rx_splice+0xafc/0xe20 [smc] smc_rx_splice+0x756/0xe20 [smc]) smc_rx_recvmsg+0xa74/0xe00 [smc] smc_splice_read+0x1ce/0x3b0 [smc] sock_splice_read+0xa2/0xf0 do_splice_read+0x198/0x240 splice_file_to_pipe+0x7e/0x110 do_splice+0x59e/0xde0 __do_splice+0x11a/0x2d0 __s390x_sys_splice+0x140/0x1f0 __do_syscall+0x122/0x280 system_call+0x6e/0x90 Last Breaking-Event-Address: smc_rx_splice+0x960/0xe20 [smc] ---[ end trace 0000000000000000 ]---

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A flaw in the Linux kernel’s SMC networking code can leave received data referencing freed memory. A local, low-privileged user able to exercise the affected splice path could potentially crash the system or compromise confidentiality and integrity. The supplied CVSS score is 7.8 (high).

Executive priority

Treat as a high-priority kernel update for systems using SMC or permitting untrusted local users. It is less urgent where SMC is unavailable and local access is tightly controlled. There is no supplied evidence of active exploitation, but the potential impact spans system confidentiality, integrity, and availability.

Technical view

smc_lo_register_dmb() allocated DMB buffers with kzalloc(), but smc_rx_splice() passed them to get_page(). Because this memory was not page-backed, reference counting failed, creating a possible use-after-free before splice_to_pipe() completed. The published fix uses folio_alloc() so the buffers are page-backed.

Likely exposure

Exposure requires an affected Linux kernel and access to the SMC receive-and-splice path. The bundle lists Linux 6.10, 6.12.50, 6.16.10, and 6.17 as affected, but its version data is incomplete or ambiguous. Confirm distribution-specific applicability and SMC usage.

Exploitation context

The CVSS vector describes local access, low privileges, low complexity, no user interaction, and potential high confidentiality, integrity, and availability impact. The bundle marks this CVE as absent from KEV and provides no evidence of active exploitation or a public exploit.

Researcher notes

The root issue is an invalid lifetime assumption: kmalloc-backed DMB memory cannot safely receive a page reference through get_page(). The fix changes allocation to folio_alloc(). The bundle supplies three stable commits but does not map each commit to an exact release range, so downstream backport verification is necessary.

Mitigation direction

  • Install a vendor-supported kernel containing the referenced upstream or stable fixes.
  • Consult the Linux distribution’s advisory to map fixed package versions accurately.
  • Prioritize systems where SMC is enabled, available, or actively used.
  • If immediate updating is impossible, seek vendor-approved guidance for limiting SMC exposure.

Validation and detection

  • Record the running kernel and distribution package versions on potentially exposed systems.
  • Compare package versions against distribution advisories and the referenced stable commits.
  • Determine whether SMC support is configured, loaded, and used by local workloads.
  • After updating, verify the running kernel includes the applicable fix.
  • Monitor kernel logs for warnings referencing smc_rx_splice or get_page.
Prepared
Confidence
high
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2025-40012 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
3Timeline events
0ADP providers
4Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9Linux

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2025-40012Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxf7a22071dbf316c982fb44308874bd7ad9ac2091, f7a22071dbf316c982fb44308874bd7ad9ac2091, f7a22071dbf316c982fb44308874bd7ad9ac2091unaffected
LinuxLinux6.10, 0, 6.12.50, 6.16.10, 6.17affected
Weakness

CWE details

No CWE listed

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