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CVE-2026-74617
dibs: initialise dibs->lock in dibs_dev_alloc()
Published 2026-08-22 (2 months ago) by the Linux kernel CNA. Subsystem drivers/dibs. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-74617 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 | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| Debian 14forky | fixed | 7.1.9-1 | Update the kernel and reboot. Fixed in 7.1.9-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.9-1 | Update the kernel and reboot. Fixed in 7.1.9-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
dibs->lock is initialised by dibs_dev_add(), but a dibs device can already take interrupts before that call: ism_probe() runs ism_dev_init(), and hence request_irq(), before it calls dibs_dev_add(). No client can have registered a dmb at that point, so no dmb interrupt can occur, but a GID event interrupt can, and ism_handle_irq() takes dibs->lock unconditionally on entry, before it inspects anything else. Initialise the lock in dibs_dev_alloc() instead, so that it is valid as soon as a driver can publish the device to its interrupt handler.
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/dibs/dibs_main.c
include/linux/dibs.h
- What this is
- DIBS (DIRECT INTERNAL BUFFER SHARING)MAINTAINERS section matched on drivers/dibs/ · netdev@vger.kernel.org · Supported
Check it on the machine
grep -w CONFIG_DIBS /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 does not build this code in 2 releases. The build rule could not be established for 2 releases, so nothing is claimed about those.
- bookworm, trixie?
- forky, sidn
- ?
- not established - no Makefile entry for the affected file
- n
- not enabled on any flavour - this release does not build the code
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
- Build switch
- CONFIG_DIBS
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
- 2026-08-22 (2 months ago)source
- CVSS
- 9.8 critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.65%, higher than 50.1% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- drivers/dibs
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.18 | 6.18.45 | fe79571f4043 |
| 6.18 | 7.1.9 | 2926031acba1 |
| 6.18 | 7.2 | c27e36054537 |
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:NAttack vector, network
- On IBM Z SMC-D systems, a remote networked peer on the shared ISM fabric can emit GID/IEQ fabric events that raise ISM MSI interrupts during ism_probe, reaching ism_handle_irq() without any local syscall or ioctl on the victim.
- AC:LAttack complexity, low
- The attacker controls timing by repeatedly sending ISM GID/IEQ fabric events (or coordinating with victim reboot/module reprobe) to hit the probe window between request_irq() and dibs_dev_add(), rather than depending on uncontrollable memory layout.
- PR:NPrivileges required, none
- Exploitation is driven by ISM hardware interrupts from fabric events and does not require local credentials, capabilities, or namespaces on the victim; a remote/co-tenant ISM fabric peer can trigger the IRQ path during device bring-up.
- UI:NUser interaction, none
- The race occurs automatically during kernel boot or ISM driver probe when fabric GID events arrive; no victim user action such as mounting a filesystem or opening a device node is required.
- S:UScope, unchanged
- The flaw corrupts kernel driver state via an uninitialized spinlock in IRQ context but does not cross a VM, IOMMU, or sandbox security boundary; impact remains within kernel privilege.
- C:HConfidentiality impact, high
- Calling spin_lock() on an uninitialized dibs->lock is undefined behavior that can corrupt lock metadata and adjacent dibs_dev fields, creating a memory-safety primitive that can be leveraged for arbitrary kernel memory disclosure.
- I:HIntegrity impact, high
- Broken spinlock initialization can permit unsafe concurrent access to dibs_dev state and enable arbitrary kernel memory writes or control-flow hijacking, not merely a clean denial of service.
- A:HAvailability impact, high
- Taking an uninitialized spinlock in ism_handle_irq() can trigger kernel BUG/oops/panic or wedge ISM interrupt handling, causing a high-severity system crash or hang on affected IBM Z hosts.