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CVE-2026-80979
net/smc: unregister the connection before draining the rx tasklet
Published 2026-09-11 (37 days ago) by the Linux kernel CNA. Subsystem net/smc. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-80979 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
smc_conn_free() calls smc_ism_unset_conn() only while the link group is still on its device list, and never sets conn->killed. smc_lgr_terminate_sched() unlinks the group immediately and defers killing its connections to a work item, so a connection freed in that window keeps its smcd->conn[] slot with both gates in smcd_handle_irq() open, and the device can re-arm the receive tasklet after tasklet_kill() has returned. On the DMB-nocopy path the ghost send buffer is freed right after that drain, so the re-armed tasklet dereferences it. Unregister unconditionally and drain before the detach at both teardown sites, mirroring rmb_desc, which smc_buf_unuse() releases after the drain. Clear conn->sndbuf_desc before freeing it as well, so a reader that samples the pointer cannot get one that is already freed.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
net/smc/smc_core.c
- What this is
- SHARED MEMORY COMMUNICATIONS (SMC) SOCKETSMAINTAINERS section matched on net/smc/ · linux-rdma@vger.kernel.org · Supported
- Kernel module
- smc
Check it on the machine
grep -w CONFIG_SMC /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w smcPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian does not build this code in 2 releases. It does build it in 3 releases, so the answer depends on which release the machine runs.
- bookworm, trixiem
- forky, sidn
- bookworm · linux-6.12m
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- n
- not enabled on any flavour - this release does not build the code
- Build switch
- CONFIG_SMC
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-09-11 (37 days ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.13%, higher than 2.2% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- net/smc
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.6.66 | 6.6.157 | b6b6ac713ee8 |
| 6.10 | 6.12.109 | b4d540ac95cd |
| 6.10 | 6.18.50 | 5bd8b764a610 |
| 6.10 | 7.2.4 | b74d313567df |
| 6.10 | 7.3 | 36cdf5d48ca1 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The UAF is on the SMC-D DMB-nocopy teardown path, which only loopback-ISM implements; that device accepts a peer only when the GID matches this host, so a local AF_SMC/IPPROTO_SMC pair reaches smc_conn_free()/smcd_handle_irq(), and a remote TCP/CLC peer cannot attach to that fabric.
- AC:LAttack complexity, low
- The attacker owns both sockets and can send on one endpoint to arm smcd_handle_irq() while close() on the other runs smc_conn_free()/smc_conn_kill, which kfree sndbuf_desc before tasklet_kill; they control both sides of the race, so complexity is Low.
- PR:LPrivileges required, low
- socket(AF_SMC) and IPPROTO_SMC listen/connect on ephemeral ports need no capabilities, and loopback-ISM is usable from a user network namespace, so only an unprivileged local account is required.
- UI:NUser interaction, none
- The attacker performs connect, send, and close on their own SMC sockets; no separate victim action such as mounting a filesystem or opening a file is required.
- S:UScope, unchanged
- The freed object is a kernel kmalloc smc_buf_desc processed by a tasklet in the same kernel; this is privilege escalation within one security authority, not a VM, IOMMU, or sandbox escape.
- C:HConfidentiality impact, high
- smcd_cdc_rx_tsklet/smc_cdc_msg_recv_action dereference the freed ghost sndbuf_desc (including ->len); a slab use-after-free of a kmalloc object that the attacker can spray yields an arbitrary kernel read.
- I:HIntegrity impact, high
- The same tasklet continues into cursor updates and smc_tx_pending() which write through the recycled descriptor, so heap spraying the use-after-free provides an arbitrary kernel write and control-flow hijack primitive.
- A:HAvailability impact, high
- Tasklet use of the freed smc_buf_desc oopses or panics the kernel even without a full exploit, causing a full system availability loss that the attacker can repeat.