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CVE-2024-50028
thermal: core: Reference count the zone in thermal_zone_get_by_id()
Published 2024-10-21 (24 months ago) by the Linux kernel CNA. Subsystem drivers/thermal. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2024-50028 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 | vulnerable | 6.1.190-1 | No fix published anywhere yet, neither in Debian nor upstream for the series bookworm tracks. Watch the Debian tracker page for this CVE. Advisories for bookworm have historically landed a median of 23 days after publication. |
| Debian 13trixie | fixed | 6.11.4-1 | Update the kernel and reboot. Fixed in 6.11.4-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 6.11.4-1 | Update the kernel and reboot. Fixed in 6.11.4-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 6.11.4-1 | Update the kernel and reboot. Fixed in 6.11.4-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
There are places in the thermal netlink code where nothing prevents the thermal zone object from going away while being accessed after it has been returned by thermal_zone_get_by_id(). To address this, make thermal_zone_get_by_id() get a reference on the thermal zone device object to be returned with the help of get_device(), under thermal_list_lock, and adjust all of its callers to this change with the help of the cleanup.h infrastructure.
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.
drivers/thermal/thermal_core.c
drivers/thermal/thermal_core.h
drivers/thermal/thermal_netlink.c
- What this is
- THERMALMAINTAINERS section matched on drivers/thermal/ · linux-pm@vger.kernel.org · Supported
Check it on the machine
grep -w CONFIG_THERMAL /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.
Show whether Debian builds this, per release
Debian builds this code. Every release below compiles the affected file into the kernels it ships.
- bookworm, trixie, forky, sidy
- y
- built into the kernel image on every flavour - only a patch removes it
- Build switch
- CONFIG_THERMAL
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
- 2024-10-21 (24 months 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
- 0.22%, higher than 11.3% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/thermal
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.9 | 6.11.4 | c95538b286ef |
| 5.9 | 6.12 | a42a5839f400 |
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 vulnerable handlers are reached through the thermal generic-netlink family via a local AF_NETLINK socket, not from any remote peer. Per kernel scoring guidance, netlink-reachable code is Local.
- AC:LAttack complexity, low
- The attacker fully controls and can continuously repeat the read side (unlimited TZ_GET_TEMP/TRIP/GOV requests from many threads), and the free side leaves a very wide window (list_del under thermal_list_lock, then cancel_delayed_work_sync, device_del and wait_for_completion before kfree), so a zone teardown from any routine event (driver/module removal, device hot-unplug, power-supply/charger removal, CPU hotplug or suspend/resume) is reliably won; the stale pointer can also be held across preemption.
- PR:LPrivileges required, low
- The thermal genl ops carry no GENL_ADMIN_PERM or GENL_UNS_ADMIN_PERM flag, so genl_family_rcv_msg() applies no capability check — any unprivileged local user can open NETLINK_GENERIC and issue these commands with an arbitrary zone id.
- UI:NUser interaction, none
- Exploitation is entirely driven by the attacker's own netlink requests plus a concurrent zone teardown; no victim action is needed at any point.
- S:UScope, unchanged
- The use-after-free corrupts kernel heap memory within the same kernel security authority, with no crossing of a VM, IOMMU, or sandbox boundary.
- C:HConfidentiality impact, high
- Contents of the freed thermal_zone_device are copied directly back to the attacker in the netlink reply — trip temperatures/types, the governor name via a stale tz->governor pointer dereference, and a trip loop bounded by num_trips read from freed memory, giving an effectively unbounded heap read primitive after reclaim.
- I:HIntegrity impact, high
- The handlers write into the freed object (mutex_lock on tz->lock) and, in the GET_TEMP path, make an indirect call through tz->ops.get_temp read out of freed slab memory, which after a heap spray yields attacker-controlled control-flow hijack and arbitrary kernel modification.
- A:HAvailability impact, high
- Even unweaponized, dereferencing and locking the freed thermal zone (and calling a stale ops pointer) causes memory corruption and kernel oops/panic, repeatable at will by an unprivileged process.