CVE-2025-68209

What the bug is

Currently, CQs without a completion function are assigned the mlx5_add_cq_to_tasklet function by default. This is problematic since only user CQs created through the mlx5_ib driver are intended to use this function. Additionally, all CQs that will use doorbells instead of polling for completions must call mlx5_cq_arm. However, the default CQ creation flow leaves a valid value in the CQ's arm_db field, allowing FW to send interrupts to polling-only CQs in certain corner cases. These two factors would allow a polling-only kernel CQ to be triggered by an EQ interrupt and call a completion function intended only for user CQs, causing a null pointer exception. Some areas in the driver have prevented this issue with one-off fixes but did not address the root cause. This patch fixes the described issue by adding defaults to the create CQ flow. It adds a default dummy completion function to protect against null pointer exceptions, and it sets an invalid command sequence number by default in kernel CQs to prevent the FW from sending an interrupt to the CQ until it is armed. User CQs are responsible for their own initialization values. Callers of mlx5_core_create_cq are responsible for changing the completion function and arming the CQ per their needs.

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/infiniband/hw/mlx5/cq.c
drivers/net/ethernet/mellanox/mlx5/core/cq.c
drivers/net/ethernet/mellanox/mlx5/core/en_main.c
drivers/net/ethernet/mellanox/mlx5/core/fpga/conn.c
drivers/net/ethernet/mellanox/mlx5/core/steering/hws/send.c
drivers/net/ethernet/mellanox/mlx5/core/steering/sws/dr_send.c
drivers/vdpa/mlx5/net/mlx5_vnet.c
include/linux/mlx5/cq.h

What this is

MELLANOX MLX5 IB driverMAINTAINERS section matched on drivers/infiniband/hw/mlx5/ · linux-rdma@vger.kernel.org · Supported

Kernel module

mlx5_ib

Check it on the machine

grep -wE 'CONFIG_INFINIBAND|CONFIG_MLX5_INFINIBAND' /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 mlx5_ib

Prints 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 builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.

• bookwormm
• trixieMnot built on armel/rpi
• forky, sidm

m

a loadable module on every flavour - check lsmod, can be blacklisted

M

a module where it is built at all; some flavours do not build it

Build switches

CONFIG_INFINIBAND, CONFIG_MLX5_INFINIBAND

Reads as

all on means the file is compiled; any one off means it is not.

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

2025-12-16 (10 months ago)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

0.18%, higher than 7.5% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

not yet assignedsource

Subsystem

drivers/infiniband

Upstream fixes

The versions the CNA records as introducing and fixing this, and the commit for each. source

Introduced	Fixed in	Commit
6.0	6.17.9	08469f5393a1
6.0	6.18	e5eba42f0134