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CVE Record

CVE-2022-49979: net: fix refcount bug in sk_psock_get (2)

In the Linux kernel, the following vulnerability has been resolved: net: fix refcount bug in sk_psock_get (2) Syzkaller reports refcount bug as follows: ------------[ cut here ]------------ refcount_t: saturated; leaking memory. WARNING: CPU: 1 PID: 3605 at lib/refcount.c:19 refcount_warn_saturate+0xf4/0x1e0 lib/refcount.c:19 Modules linked in: CPU: 1 PID: 3605 Comm: syz-executor208 Not tainted 5.18.0-syzkaller-03023-g7e062cda7d90 #0 <TASK> __refcount_add_not_zero include/linux/refcount.h:163 [inline] __refcount_inc_not_zero include/linux/refcount.h:227 [inline] refcount_inc_not_zero include/linux/refcount.h:245 [inline] sk_psock_get+0x3bc/0x410 include/linux/skmsg.h:439 tls_data_ready+0x6d/0x1b0 net/tls/tls_sw.c:2091 tcp_data_ready+0x106/0x520 net/ipv4/tcp_input.c:4983 tcp_data_queue+0x25f2/0x4c90 net/ipv4/tcp_input.c:5057 tcp_rcv_state_process+0x1774/0x4e80 net/ipv4/tcp_input.c:6659 tcp_v4_do_rcv+0x339/0x980 net/ipv4/tcp_ipv4.c:1682 sk_backlog_rcv include/net/sock.h:1061 [inline] __release_sock+0x134/0x3b0 net/core/sock.c:2849 release_sock+0x54/0x1b0 net/core/sock.c:3404 inet_shutdown+0x1e0/0x430 net/ipv4/af_inet.c:909 __sys_shutdown_sock net/socket.c:2331 [inline] __sys_shutdown_sock net/socket.c:2325 [inline] __sys_shutdown+0xf1/0x1b0 net/socket.c:2343 __do_sys_shutdown net/socket.c:2351 [inline] __se_sys_shutdown net/socket.c:2349 [inline] __x64_sys_shutdown+0x50/0x70 net/socket.c:2349 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x46/0xb0 </TASK> During SMC fallback process in connect syscall, kernel will replaces TCP with SMC. In order to forward wakeup smc socket waitqueue after fallback, kernel will sets clcsk->sk_user_data to origin smc socket in smc_fback_replace_callbacks(). Later, in shutdown syscall, kernel will calls sk_psock_get(), which treats the clcsk->sk_user_data as psock type, triggering the refcnt warning. So, the root cause is that smc and psock, both will use sk_user_data field. So they will mismatch this field easily. This patch solves it by using another bit(defined as SK_USER_DATA_PSOCK) in PTRMASK, to mark whether sk_user_data points to a psock object or not. This patch depends on a PTRMASK introduced in commit f1ff5ce2cd5e ("net, sk_msg: Clear sk_user_data pointer on clone if tagged"). For there will possibly be more flags in the sk_user_data field, this patch also refactor sk_user_data flags code to be more generic to improve its maintainability.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A Linux networking flaw can misinterpret internal socket data during SMC fallback and shutdown, corrupting reference-count handling and potentially leaking memory. The supplied CVSS score is 7.8 (high), but the public description demonstrates a kernel warning rather than confirmed code execution or real-world compromise.

Executive priority

Treat this as a high-priority kernel maintenance issue, especially on shared or locally accessible Linux hosts. It does not warrant an exploitation emergency based solely on the supplied evidence. Confirm exposure promptly, deploy supported kernel fixes through normal accelerated patching, and require reboot verification.

Technical view

SMC fallback and psock both use sk_user_data. During socket replacement, an SMC pointer can be treated as a psock by sk_psock_get(), causing reference-count saturation and memory leakage. The fix tags psock pointers with SK_USER_DATA_PSOCK and generalizes flag handling. It depends on an earlier PTRMASK change.

Likely exposure

Exposure applies to Linux kernels identified as affected in the CVE data, including listed 5.17, 5.15.65, 5.19.7, and 6.0 entries. The supplied version boundaries mix releases and commit identifiers, so distribution-specific applicability requires confirmation against vendor advisories and kernel build provenance.

Exploitation context

The CVSS vector describes local, low-complexity exploitation requiring low privileges and no user interaction. The issue was reported by Syzkaller. It is not listed as KEV in the supplied bundle, and no cited evidence establishes active exploitation, a public weaponized exploit, or a demonstrated path beyond the reported refcount failure.

Researcher notes

The trigger involves SMC fallback replacing TCP callbacks, leaving sk_user_data pointing to an SMC socket before shutdown reaches sk_psock_get(). The fix adds explicit pointer tagging to prevent type mismatch. Although CVSS assigns high confidentiality, integrity, and availability impacts, the supplied technical evidence directly documents refcount saturation and memory leakage only.

Mitigation direction

  • Identify running kernel versions and distribution patch levels on Linux systems.
  • Apply the vendor-supported kernel update containing the referenced stable fix.
  • Prioritize multi-user systems where untrusted users can execute local processes.
  • If updates are unavailable, consult distribution guidance for supported mitigations; none are specified in the supplied sources.

Validation and detection

  • Compare installed kernel builds with distribution advisories and the CVE's fixed commits.
  • Confirm updated kernels include the SK_USER_DATA_PSOCK tagging change and its PTRMASK dependency.
  • Reboot into the updated kernel and verify the active version, not merely the installed package.
  • Monitor kernel logs for refcount saturation warnings involving sk_psock_get or tls_data_ready.
Prepared
Confidence
medium
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-2022-49979 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-2022-49979Attack 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
LinuxLinux0ef6049f664941bc0f75828b3a61877635048b27, 341adeec9adad0874f29a0a1af35638207352a39, 341adeec9adad0874f29a0a1af35638207352a39, 504078fbe9dd570d685361b57784a6050bc40aaa, 5.15.22, 5.16.8unaffected
LinuxLinux5.17, 0, 5.15.65, 5.19.7, 6.0affected
Weakness

CWE details

No CWE listed

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