published May 20, 2025
In the Linux kernel, the following vulnerability has been resolved:
firmware: arm_scmi: Balance device refcount when destroying devices
Using device_find_child() to lookup the proper SCMI device to destroy
causes an unbalance in device refcount, since device_find_child() calls an
implicit get_device(): this, in turns, inhibits the call of the provided
release methods upon devices destruction.
As a consequence, one of the structures that is not freed properly upon
destruction is the internal struct device_private dev->p populated by the
drivers subsystem core.
KMemleak detects this situation since loading/unloding some SCMI driver
causes related devices to be created/destroyed without calling any
device_release method.
unreferenced object 0xffff00000f583800 (size 512):
comm "insmod", pid 227, jiffies 4294912190
hex dump (first 32 bytes):
00 00 00 00 ad 4e ad de ff ff ff ff 00 00 00 00 .....N..........
ff ff ff ff ff ff ff ff 60 36 1d 8a 00 80 ff ff ........`6......
backtrace (crc 114e2eed):
kmemleak_alloc+0xbc/0xd8
__kmalloc_cache_noprof+0x2dc/0x398
device_add+0x954/0x12d0
device_register+0x28/0x40
__scmi_device_create.part.0+0x1bc/0x380
scmi_device_create+0x2d0/0x390
scmi_create_protocol_devices+0x74/0xf8
scmi_device_request_notifier+0x1f8/0x2a8
notifier_call_chain+0x110/0x3b0
blocking_notifier_call_chain+0x70/0xb0
scmi_driver_register+0x350/0x7f0
0xffff80000a3b3038
do_one_initcall+0x12c/0x730
do_init_module+0x1dc/0x640
load_module+0x4b20/0x5b70
init_module_from_file+0xec/0x158
$ ./scripts/faddr2line ./vmlinux device_add+0x954/0x12d0
device_add+0x954/0x12d0:
kmalloc_noprof at include/linux/slab.h:901
(inlined by) kzalloc_noprof at include/linux/slab.h:1037
(inlined by) device_private_init at drivers/base/core.c:3510
(inlined by) device_add at drivers/base/core.c:3561
Balance device refcount by issuing a put_device() on devices found via
device_find_child().