CVE-2026-64328

What the bug is

In ffs_dmabuf_transfer(), a ffs_dma_fence object is kmalloc'd, with the underlying dma_fence later initialized by dma_fence_init(), which sets its kref counter to 1. Then, dma_resv_add_fence() gets a second reference, and a pointer to the ffs_dma_fence is passed as the usb_request's "context" field. The dma-resv mechanism will manage the second reference, but the first reference is never properly released; the ffs_dmabuf_cleanup() function decreases the reference count, but only to balance with the reference grab in ffs_dmabuf_signal_done(). The code will then slowly leak memory as more ffs_dma_fence objects are created without being ever freed. Address this issue by transferring ownership of the fence to the DMA reservation object, by calling dma_fence_put() right after dma_resv_add_fence(). The ffs_dma_fence then gets properly discarded after being signalled.

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/usb/gadget/function/f_fs.c

What this is

USB SUBSYSTEMMAINTAINERS section matched on drivers/usb/ · linux-usb@vger.kernel.org · Supported

Kernel module

usb_f_fs

Check it on the machine

grep -wE 'CONFIG_OF|CONFIG_PCI|CONFIG_USB|CONFIG_USB_F_FS|CONFIG_USB_GADGET|CONFIG_USB_PHY|CONFIG_USB_SUPPORT' /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 usb_f_fs

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.

• bookwormMnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt/amd64, arm64/cloud-arm64, i386/686, i386/686-pae, i386/rt/686-pae, ppc64el/powerpc64le
• trixieMnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt/amd64, arm64/cloud-arm64, armel/rpi, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, s390x/s390x
• forky, sidMnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt-amd64, arm64/cloud-arm64, loong64/loong64, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, s390x/s390x
• bookworm · linux-6.12Mnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt/amd64, arm64/cloud-arm64, ppc64el/powerpc64le, ppc64el/powerpc64le-64k

M

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

Build switches

CONFIG_OF, CONFIG_PCI, CONFIG_USB, CONFIG_USB_F_FS, CONFIG_USB_GADGET, CONFIG_USB_PHY, CONFIG_USB_SUPPORT

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

2026-07-25 (3 months ago)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

0.16%, higher than 4.6% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

unimportantsource

Subsystem

drivers/usb

Upstream fixes

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

Introduced	Fixed in	Commit
6.9	6.12.96	b7475b2dce5e
6.9	6.18.39	e086c16962a1
6.9	7.1.4	0cae3d610942
6.9	7.2	baa6b6068a3f

Debian advisories