6.6-stable review patch. If anyone has any objections, please let me know.
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From: Cristian Marussi cristian.marussi@arm.com
[ Upstream commit 9ca67840c0ddf3f39407339624cef824a4f27599 ]
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().
Reported-by: Alice Ryhl aliceryhl@google.com Closes: https://lore.kernel.org/linux-arm-kernel/Z8nK3uFkspy61yjP@arm.com/T/#mc1f73a... CC: Sudeep Holla sudeep.holla@arm.com CC: Catalin Marinas catalin.marinas@arm.com Fixes: d4f9dddd21f3 ("firmware: arm_scmi: Add dynamic scmi devices creation") Signed-off-by: Cristian Marussi cristian.marussi@arm.com Tested-by: Alice Ryhl aliceryhl@google.com Message-Id: 20250306185447.2039336-1-cristian.marussi@arm.com Signed-off-by: Sudeep Holla sudeep.holla@arm.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/firmware/arm_scmi/bus.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/drivers/firmware/arm_scmi/bus.c b/drivers/firmware/arm_scmi/bus.c index dcf774d3edfe4..51eeaf14367da 100644 --- a/drivers/firmware/arm_scmi/bus.c +++ b/drivers/firmware/arm_scmi/bus.c @@ -240,6 +240,9 @@ static struct scmi_device *scmi_child_dev_find(struct device *parent, if (!dev) return NULL;
+ /* Drop the refcnt bumped implicitly by device_find_child */ + put_device(dev); + return to_scmi_dev(dev); }