Upstream information
Description
In the Linux kernel, the following vulnerability has been resolved:net/smc: fix NULL dereference and UAF in smc_tcp_syn_recv_sock()
Syzkaller reported a panic in smc_tcp_syn_recv_sock() [1].
smc_tcp_syn_recv_sock() is called in the TCP receive path
(softirq) via icsk_af_ops->syn_recv_sock on the clcsock (TCP
listening socket). It reads sk_user_data to get the smc_sock
pointer. However, when the SMC listen socket is being closed
concurrently, smc_close_active() sets clcsock->sk_user_data
to NULL under sk_callback_lock, and then the smc_sock itself
can be freed via sock_put() in smc_release().
This leads to two issues:
1) NULL pointer dereference: sk_user_data is NULL when
accessed.
2) Use-after-free: sk_user_data is read as non-NULL, but the
smc_sock is freed before its fields (e.g., queued_smc_hs,
ori_af_ops) are accessed.
The race window looks like this (the syzkaller crash [1]
triggers via the SYN cookie path: tcp_get_cookie_sock() ->
smc_tcp_syn_recv_sock(), but the normal tcp_check_req() path
has the same race):
CPU A (softirq) CPU B (process ctx)
tcp_v4_rcv()
TCP_NEW_SYN_RECV:
sk = req->rsk_listener
sock_hold(sk)
/* No lock on listener */
smc_close_active():
write_lock_bh(cb_lock)
sk_user_data = NULL
write_unlock_bh(cb_lock)
...
smc_clcsock_release()
sock_put(smc->sk) x2
-> smc_sock freed!
tcp_check_req()
smc_tcp_syn_recv_sock():
smc = user_data(sk)
-> NULL or dangling
smc->queued_smc_hs
-> crash!
Note that the clcsock and smc_sock are two independent objects
with separate refcounts. TCP stack holds a reference on the
clcsock, which keeps it alive, but this does NOT prevent the
smc_sock from being freed.
Fix this by using RCU and refcount_inc_not_zero() to safely
access smc_sock. Since smc_tcp_syn_recv_sock() is called in
the TCP three-way handshake path, taking read_lock_bh on
sk_callback_lock is too heavy and would not survive a SYN
flood attack. Using rcu_read_lock() is much more lightweight.
- Set SOCK_RCU_FREE on the SMC listen socket so that
smc_sock freeing is deferred until after the RCU grace
period. This guarantees the memory is still valid when
accessed inside rcu_read_lock().
- Use rcu_read_lock() to protect reading sk_user_data.
- Use refcount_inc_not_zero(&smc->sk.sk_refcnt) to pin the
smc_sock. If the refcount has already reached zero (close
path completed), it returns false and we bail out safely.
Note: smc_hs_congested() has a similar lockless read of
sk_user_data without rcu_read_lock(), but it only checks for
NULL and accesses the global smc_hs_wq, never dereferencing
any smc_sock field, so it is not affected.
Reproducer was verified with mdelay injection and smc_run,
the issue no longer occurs with this patch applied.
[1] https://syzkaller.appspot.com/bug?extid=827ae2bfb3a3529333e9
SUSE information
Overall state of this security issue: Pending
This issue is currently rated as having important severity.
| CVSS detail | SUSE |
|---|---|
| Base Score | 7 |
| Vector | CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H |
| Attack Vector | Local |
| Attack Complexity | High |
| Privileges Required | Low |
| User Interaction | None |
| Scope | Unchanged |
| Confidentiality Impact | High |
| Integrity Impact | High |
| Availability Impact | High |
| CVSSv3 Version | 3.1 |
| CVSS detail | SUSE |
|---|---|
| Base Score | 7.3 |
| Vector | CVSS:4.0/AV:L/AC:H/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N |
| Attack Vector | Local |
| Attack Complexity | High |
| Attack Requirements | None |
| Privileges Required | Low |
| User Interaction | None |
| Vulnerable System Confidentiality Impact | High |
| Vulnerable System Integrity Impact | High |
| Vulnerable System Availability Impact | High |
| Subsequent System Confidentiality Impact | None |
| Subsequent System Integrity Impact | None |
| Subsequent System Availability Impact | None |
| CVSSv4 Version | 4.0 |
Note from the SUSE Security Team on the kernel-default package
SUSE will no longer fix all CVEs in the Linux Kernel anymore, but declare some bug classes as won't fix. Please refer to TID 21496 for more details. SUSE Bugzilla entries: 1261584 [NEW], 1262214 [NEW] No SUSE Security Announcements cross referenced.Status of this issue by product and package
Please note that this evaluation state might be work in progress, incomplete or outdated. Also information for service packs in the LTSS phase is only included for issues meeting the LTSS criteria. If in doubt, feel free to contact us for clarification. The updates are grouped by state of their lifecycle. SUSE product lifecycles are documented on the lifecycle page.
| Product(s) | Source package | State |
|---|---|---|
| Products under general support and receiving all security fixes. | ||
| SUSE Linux Enterprise Desktop 15 SP7 | kernel-default | Affected |
| SUSE Linux Enterprise Desktop 15 SP7 | kernel-source | In progress |
| SUSE Linux Enterprise High Availability Extension 15 SP7 | kernel-default | Affected |
| SUSE Linux Enterprise High Availability Extension 15 SP7 | kernel-source | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP7 | kernel-default | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP7 | kernel-source | In progress |
| SUSE Linux Enterprise High Performance Computing 15 SP7 | kernel-source-azure | Affected |
| SUSE Linux Enterprise Live Patching 15 SP7 | kernel-default | Affected |
| SUSE Linux Enterprise Live Patching 15 SP7 | kernel-source | Affected |
| SUSE Linux Enterprise Micro 5.2 | kernel-default | Not affected |
| SUSE Linux Enterprise Micro 5.2 | kernel-rt | Not affected |
| SUSE Linux Enterprise Micro 5.2 | kernel-source | Not affected |
| SUSE Linux Enterprise Micro 5.2 | kernel-source-rt | Not affected |
| SUSE Linux Enterprise Micro 5.3 | kernel-default | Not affected |
| SUSE Linux Enterprise Micro 5.3 | kernel-rt | Not affected |
| SUSE Linux Enterprise Micro 5.3 | kernel-source | Not affected |
| SUSE Linux Enterprise Micro 5.3 | kernel-source-rt | Not affected |
| SUSE Linux Enterprise Micro 5.4 | kernel-default | Not affected |
| SUSE Linux Enterprise Micro 5.4 | kernel-rt | Not affected |
| SUSE Linux Enterprise Micro 5.4 | kernel-source | Not affected |
| SUSE Linux Enterprise Micro 5.4 | kernel-source-rt | Not affected |
| SUSE Linux Enterprise Micro 5.5 | kernel-default | Affected |
| SUSE Linux Enterprise Micro 5.5 | kernel-source | Affected |
| SUSE Linux Enterprise Micro 5.5 | kernel-source-rt | Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP7 | kernel-default | Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP7 | kernel-source | In progress |
| SUSE Linux Enterprise Module for Development Tools 15 SP7 | kernel-default | Affected |
| SUSE Linux Enterprise Module for Development Tools 15 SP7 | kernel-source | In progress |
| SUSE Linux Enterprise Module for Legacy 15 SP7 | kernel-default | Affected |
| SUSE Linux Enterprise Module for Legacy 15 SP7 | kernel-source | Affected |
| SUSE Linux Enterprise Module for Public Cloud 15 SP7 | kernel-default | Affected |
| SUSE Linux Enterprise Module for Public Cloud 15 SP7 | kernel-source | Affected |
| SUSE Linux Enterprise Module for Public Cloud 15 SP7 | kernel-source-azure | Affected |
| SUSE Linux Enterprise Real Time 15 SP7 | kernel-source-rt | In progress |
| SUSE Linux Enterprise Server 15 SP7 | kernel-default | Affected |
| SUSE Linux Enterprise Server 15 SP7 | kernel-source | In progress |
| SUSE Linux Enterprise Server 15 SP7 | kernel-source-azure | Affected |
| SUSE Linux Enterprise Server 16.0 | kernel-source | Affected |
| SUSE Linux Enterprise Server 16.1 | kernel-source | Not affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP7 | kernel-default | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP7 | kernel-source | In progress |
| SUSE Linux Enterprise Server for SAP Applications 15 SP7 | kernel-source-azure | Affected |
| SUSE Linux Enterprise Server for SAP applications 16.0 | kernel-source | Affected |
| SUSE Linux Enterprise Server for SAP applications 16.1 | kernel-source | Not affected |
| SUSE Linux Enterprise Workstation Extension 15 SP7 | kernel-default | Affected |
| SUSE Linux Enterprise Workstation Extension 15 SP7 | kernel-source | Affected |
| SUSE Linux Micro 6.0 | kernel-default | Affected |
| SUSE Linux Micro 6.0 | kernel-source | Affected |
| SUSE Linux Micro 6.0 | kernel-source-rt | Affected |
| SUSE Linux Micro 6.1 | kernel-default | Affected |
| SUSE Linux Micro 6.1 | kernel-source | Affected |
| SUSE Linux Micro 6.1 | kernel-source-rt | Affected |
| SUSE Linux Micro 6.2 | kernel-default | Affected |
| SUSE Linux Micro 6.2 | kernel-source | Affected |
| SUSE Real Time Module 15 SP7 | kernel-source-rt | In progress |
| openSUSE Leap 15.6 | kernel-default | Affected |
| openSUSE Leap 15.6 | kernel-source | Affected |
| openSUSE Leap 15.6 | kernel-source-azure | Unsupported |
| openSUSE Leap 15.6 | kernel-source-rt | Unsupported |
| Products under Long Term Service Pack support and receiving important and critical security fixes. | ||
| SUSE Linux Enterprise High Performance Computing 15 SP4 | kernel-source | Not affected |
| SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS | kernel-default | Not affected |
| SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS | kernel-source | Not affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5 | kernel-source | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS | kernel-default | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS | kernel-source | Affected |
| SUSE Linux Enterprise Live Patching 12 SP5 | kernel-default | Not affected |
| SUSE Linux Enterprise Live Patching 12 SP5 | kernel-source | Not affected |
| SUSE Linux Enterprise Live Patching 15 SP4 | kernel-default | Not affected |
| SUSE Linux Enterprise Live Patching 15 SP4 | kernel-source | Not affected |
| SUSE Linux Enterprise Live Patching 15 SP5 | kernel-default | Affected |
| SUSE Linux Enterprise Live Patching 15 SP5 | kernel-source | Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP4 | kernel-source | Not affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP5 | kernel-source | Affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP6 | kernel-source | Affected |
| SUSE Linux Enterprise Module for Development Tools 15 SP4 | kernel-source | Not affected |
| SUSE Linux Enterprise Module for Development Tools 15 SP5 | kernel-source | Affected |
| SUSE Linux Enterprise Module for Development Tools 15 SP6 | kernel-source | Affected |
| SUSE Linux Enterprise Server 11 SP4 LTSS EXTREME CORE | kernel-default | Not affected |
| SUSE Linux Enterprise Server 11 SP4 LTSS EXTREME CORE | kernel-source | Not affected |
| SUSE Linux Enterprise Server 12 SP5 | kernel-source | Not affected |
| SUSE Linux Enterprise Server 12 SP5-LTSS | kernel-default | Not affected |
| SUSE Linux Enterprise Server 12 SP5-LTSS | kernel-source | Not affected |
| SUSE Linux Enterprise Server 12 SP5-LTSS Extended Security | kernel-default | Not affected |
| SUSE Linux Enterprise Server 12 SP5-LTSS Extended Security | kernel-source | Not affected |
| SUSE Linux Enterprise Server 15 SP4 | kernel-source | Not affected |
| SUSE Linux Enterprise Server 15 SP4-LTSS | kernel-default | Not affected |
| SUSE Linux Enterprise Server 15 SP4-LTSS | kernel-source | Not affected |
| SUSE Linux Enterprise Server 15 SP5 | kernel-source | Affected |
| SUSE Linux Enterprise Server 15 SP5-LTSS | kernel-default | Affected |
| SUSE Linux Enterprise Server 15 SP5-LTSS | kernel-source | Affected |
| SUSE Linux Enterprise Server 15 SP6 | kernel-source | Affected |
| SUSE Linux Enterprise Server 15 SP6 | kernel-source-azure | Unsupported |
| SUSE Linux Enterprise Server 15 SP6-LTSS | kernel-default | Affected |
| SUSE Linux Enterprise Server 15 SP6-LTSS | kernel-source | Affected |
| SUSE Linux Enterprise Server LTSS Extended Security 12 SP5 | kernel-source | Not affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP6 | kernel-default | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP6 | kernel-source | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP6 | kernel-source-azure | Unsupported |
| SUSE Manager Proxy 4.3 | kernel-source | Not affected |
| SUSE Manager Proxy LTS 4.3 | kernel-source | Not affected |
| SUSE Manager Retail Branch Server 4.3 | kernel-source | Not affected |
| SUSE Manager Retail Branch Server LTS 4.3 | kernel-source | Not affected |
| SUSE Manager Server 4.3 | kernel-source | Not affected |
| SUSE Manager Server LTS 4.3 | kernel-source | Not affected |
| Products past their end of life and not receiving proactive updates anymore. | ||
| SUSE CaaS Platform 4.0 | kernel-source | Not affected |
| SUSE Enterprise Storage 6 | kernel-source | Not affected |
| SUSE Enterprise Storage 7 | kernel-source | Not affected |
| SUSE Enterprise Storage 7.1 | kernel-source | Not affected |
| SUSE Linux Enterprise Desktop 11 SP4 | kernel-source | Not affected |
| SUSE Linux Enterprise Desktop 12 SP4 | kernel-source | Not affected |
| SUSE Linux Enterprise Desktop 15 SP1 | kernel-source | Not affected |
| SUSE Linux Enterprise Desktop 15 SP2 | kernel-source | Not affected |
| SUSE Linux Enterprise Desktop 15 SP3 | kernel-source | Not affected |
| SUSE Linux Enterprise Desktop 15 SP4 | kernel-source | Not affected |
| SUSE Linux Enterprise Desktop 15 SP5 | kernel-source | Affected |
| SUSE Linux Enterprise Desktop 15 SP6 | kernel-source | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP1 | kernel-source | Not affected |
| SUSE Linux Enterprise High Performance Computing 15 SP1-ESPOS | kernel-source | Not affected |
| SUSE Linux Enterprise High Performance Computing 15 SP1-LTSS | kernel-source | Not affected |
| SUSE Linux Enterprise High Performance Computing 15 SP2 | kernel-source | Not affected |
| SUSE Linux Enterprise High Performance Computing 15 SP2-ESPOS | kernel-source | Not affected |
| SUSE Linux Enterprise High Performance Computing 15 SP2-LTSS | kernel-source | Not affected |
| SUSE Linux Enterprise High Performance Computing 15 SP3 | kernel-source | Not affected |
| SUSE Linux Enterprise High Performance Computing 15 SP3-ESPOS | kernel-source | Not affected |
| SUSE Linux Enterprise High Performance Computing 15 SP3-LTSS | kernel-source | Not affected |
| SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS | kernel-source | Not affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS | kernel-source | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP6 | kernel-source | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP6 | kernel-source-azure | Unsupported |
| SUSE Linux Enterprise Micro 5.0 | kernel-default | Not affected |
| SUSE Linux Enterprise Micro 5.1 | kernel-default | Not affected |
| SUSE Linux Enterprise Micro 5.1 | kernel-rt | Not affected |
| SUSE Linux Enterprise Micro 5.1 | kernel-source-rt | Not affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP1 | kernel-source | Not affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP2 | kernel-source | Not affected |
| SUSE Linux Enterprise Module for Basesystem 15 SP3 | kernel-source | Not affected |
| SUSE Linux Enterprise Module for Development Tools 15 SP1 | kernel-source | Not affected |
| SUSE Linux Enterprise Module for Development Tools 15 SP2 | kernel-source | Not affected |
| SUSE Linux Enterprise Module for Development Tools 15 SP3 | kernel-source | Not affected |
| SUSE Linux Enterprise Module for Public Cloud 15 SP6 | kernel-source-azure | Unsupported |
| SUSE Linux Enterprise Real Time 15 SP2 | kernel-source | Not affected |
| SUSE Linux Enterprise Real Time 15 SP3 | kernel-source | Not affected |
| SUSE Linux Enterprise Real Time 15 SP3 | kernel-source-rt | Not affected |
| SUSE Linux Enterprise Real Time 15 SP4 | kernel-source | Not affected |
| SUSE Linux Enterprise Real Time 15 SP4 | kernel-source-rt | Not affected |
| SUSE Linux Enterprise Real Time 15 SP5 | kernel-source-rt | Affected |
| SUSE Linux Enterprise Real Time 15 SP6 | kernel-source-rt | Unsupported |
| SUSE Linux Enterprise Server 11 SP4 | kernel-source | Not affected |
| SUSE Linux Enterprise Server 11 SP4-LTSS | kernel-source | Not affected |
| SUSE Linux Enterprise Server 12 SP4 | kernel-source | Not affected |
| SUSE Linux Enterprise Server 12 SP4-ESPOS | kernel-source | Not affected |
| SUSE Linux Enterprise Server 12 SP4-LTSS | kernel-default | Not affected |
| SUSE Linux Enterprise Server 12 SP4-LTSS | kernel-source | Not affected |
| SUSE Linux Enterprise Server 15 SP1 | kernel-source | Not affected |
| SUSE Linux Enterprise Server 15 SP1-BCL | kernel-source | Not affected |
| SUSE Linux Enterprise Server 15 SP1-LTSS | kernel-default | Not affected |
| SUSE Linux Enterprise Server 15 SP1-LTSS | kernel-source | Not affected |
| SUSE Linux Enterprise Server 15 SP2 | kernel-source | Not affected |
| SUSE Linux Enterprise Server 15 SP2-BCL | kernel-source | Not affected |
| SUSE Linux Enterprise Server 15 SP2-LTSS | kernel-default | Not affected |
| SUSE Linux Enterprise Server 15 SP2-LTSS | kernel-source | Not affected |
| SUSE Linux Enterprise Server 15 SP3 | kernel-source | Not affected |
| SUSE Linux Enterprise Server 15 SP3-BCL | kernel-source | Not affected |
| SUSE Linux Enterprise Server 15 SP3-LTSS | kernel-default | Not affected |
| SUSE Linux Enterprise Server 15 SP3-LTSS | kernel-source | Not affected |
| SUSE Linux Enterprise Server for SAP Applications 12 SP4 | kernel-source | Not affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP1 | kernel-source | Not affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP2 | kernel-source | Not affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP3 | kernel-source | Not affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP4 | kernel-default | Not affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP4 | kernel-source | Not affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP5 | kernel-default | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP5 | kernel-source | Affected |
| SUSE Manager Proxy 4.0 | kernel-source | Not affected |
| SUSE Manager Proxy 4.1 | kernel-source | Not affected |
| SUSE Manager Proxy 4.2 | kernel-source | Not affected |
| SUSE Manager Retail Branch Server 4.0 | kernel-source | Not affected |
| SUSE Manager Retail Branch Server 4.1 | kernel-source | Not affected |
| SUSE Manager Retail Branch Server 4.2 | kernel-source | Not affected |
| SUSE Manager Server 4.0 | kernel-source | Not affected |
| SUSE Manager Server 4.1 | kernel-source | Not affected |
| SUSE Manager Server 4.2 | kernel-source | Not affected |
| SUSE OpenStack Cloud 9 | kernel-source | Not affected |
| SUSE OpenStack Cloud Crowbar 9 | kernel-source | Not affected |
| SUSE Real Time Module 15 SP3 | kernel-source-rt | Not affected |
| SUSE Real Time Module 15 SP4 | kernel-source-rt | Not affected |
| SUSE Real Time Module 15 SP5 | kernel-source-rt | Affected |
| SUSE Real Time Module 15 SP6 | kernel-source-rt | Unsupported |
| openSUSE Leap 15.3 | kernel-source | Not affected |
| openSUSE Leap 15.3 | kernel-source-rt | Not affected |
| openSUSE Leap 15.4 | kernel-source | Not affected |
| openSUSE Leap 15.4 | kernel-source-rt | Not affected |
| openSUSE Leap 15.5 | kernel-source | Affected |
| openSUSE Leap 15.5 | kernel-source-rt | Affected |
SUSE Timeline for this CVE
CVE page created: Fri Apr 3 20:02:44 2026CVE page last modified: Mon Apr 20 17:31:57 2026