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Fri, 07 Mar 2025 01:34:17 -0800 (PST) Date: Fri, 7 Mar 2025 09:34:15 +0000 In-Reply-To: <20250306185447.2039336-1-cristian.marussi@arm.com> Mime-Version: 1.0 References: <20250306185447.2039336-1-cristian.marussi@arm.com> Message-ID: Subject: Re: [PATCH] firmware: arm_scmi: Balance device refcount when destroying devices From: Alice Ryhl To: Cristian Marussi Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, arm-scmi@vger.kernel.org, Sudeep Holla , Catalin Marinas Content-Type: text/plain; charset="utf-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250307_013420_306956_9D89188A X-CRM114-Status: GOOD ( 13.68 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Mar 06, 2025 at 06:54:47PM +0000, Cristian Marussi wrote: > 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 > Closes: https://lore.kernel.org/linux-arm-kernel/Z8nK3uFkspy61yjP@arm.com/T/#mc1f73a0ea5e41014fa145147b7b839fc988ada8f > CC: Sudeep Holla > CC: Catalin Marinas > Fixes: d4f9dddd21f3 ("firmware: arm_scmi: Add dynamic scmi devices creation") > Signed-off-by: Cristian Marussi I was not able to reproduce the memory leak after applying this patch. Tested-by: Alice Ryhl