firmware: arm_scmi: Fix slab-use-after-free in scmi_bus_notifier()

The scmi_dev->name is released prematurely in __scmi_device_destroy(),
which causes slab-use-after-free when accessing scmi_dev->name in
scmi_bus_notifier(). So move the release of scmi_dev->name to
scmi_device_release() to avoid slab-use-after-free.

  |  BUG: KASAN: slab-use-after-free in strncmp+0xe4/0xec
  |  Read of size 1 at addr ffffff80a482bcc0 by task swapper/0/1
  |
  |  CPU: 1 PID: 1 Comm: swapper/0 Not tainted 6.6.38-debug #1
  |  Hardware name: Qualcomm Technologies, Inc. SA8775P Ride (DT)
  |  Call trace:
  |   dump_backtrace+0x94/0x114
  |   show_stack+0x18/0x24
  |   dump_stack_lvl+0x48/0x60
  |   print_report+0xf4/0x5b0
  |   kasan_report+0xa4/0xec
  |   __asan_report_load1_noabort+0x20/0x2c
  |   strncmp+0xe4/0xec
  |   scmi_bus_notifier+0x5c/0x54c
  |   notifier_call_chain+0xb4/0x31c
  |   blocking_notifier_call_chain+0x68/0x9c
  |   bus_notify+0x54/0x78
  |   device_del+0x1bc/0x840
  |   device_unregister+0x20/0xb4
  |   __scmi_device_destroy+0xac/0x280
  |   scmi_device_destroy+0x94/0xd0
  |   scmi_chan_setup+0x524/0x750
  |   scmi_probe+0x7fc/0x1508
  |   platform_probe+0xc4/0x19c
  |   really_probe+0x32c/0x99c
  |   __driver_probe_device+0x15c/0x3c4
  |   driver_probe_device+0x5c/0x170
  |   __driver_attach+0x1c8/0x440
  |   bus_for_each_dev+0xf4/0x178
  |   driver_attach+0x3c/0x58
  |   bus_add_driver+0x234/0x4d4
  |   driver_register+0xf4/0x3c0
  |   __platform_driver_register+0x60/0x88
  |   scmi_driver_init+0xb0/0x104
  |   do_one_initcall+0xb4/0x664
  |   kernel_init_freeable+0x3c8/0x894
  |   kernel_init+0x24/0x1e8
  |   ret_from_fork+0x10/0x20
  |
  |  Allocated by task 1:
  |   kasan_save_stack+0x2c/0x54
  |   kasan_set_track+0x2c/0x40
  |   kasan_save_alloc_info+0x24/0x34
  |   __kasan_kmalloc+0xa0/0xb8
  |   __kmalloc_node_track_caller+0x6c/0x104
  |   kstrdup+0x48/0x84
  |   kstrdup_const+0x34/0x40
  |   __scmi_device_create.part.0+0x8c/0x408
  |   scmi_device_create+0x104/0x370
  |   scmi_chan_setup+0x2a0/0x750
  |   scmi_probe+0x7fc/0x1508
  |   platform_probe+0xc4/0x19c
  |   really_probe+0x32c/0x99c
  |   __driver_probe_device+0x15c/0x3c4
  |   driver_probe_device+0x5c/0x170
  |   __driver_attach+0x1c8/0x440
  |   bus_for_each_dev+0xf4/0x178
  |   driver_attach+0x3c/0x58
  |   bus_add_driver+0x234/0x4d4
  |   driver_register+0xf4/0x3c0
  |   __platform_driver_register+0x60/0x88
  |   scmi_driver_init+0xb0/0x104
  |   do_one_initcall+0xb4/0x664
  |   kernel_init_freeable+0x3c8/0x894
  |   kernel_init+0x24/0x1e8
  |   ret_from_fork+0x10/0x20
  |
  |  Freed by task 1:
  |   kasan_save_stack+0x2c/0x54
  |   kasan_set_track+0x2c/0x40
  |   kasan_save_free_info+0x38/0x5c
  |   __kasan_slab_free+0xe8/0x164
  |   __kmem_cache_free+0x11c/0x230
  |   kfree+0x70/0x130
  |   kfree_const+0x20/0x40
  |   __scmi_device_destroy+0x70/0x280
  |   scmi_device_destroy+0x94/0xd0
  |   scmi_chan_setup+0x524/0x750
  |   scmi_probe+0x7fc/0x1508
  |   platform_probe+0xc4/0x19c
  |   really_probe+0x32c/0x99c
  |   __driver_probe_device+0x15c/0x3c4
  |   driver_probe_device+0x5c/0x170
  |   __driver_attach+0x1c8/0x440
  |   bus_for_each_dev+0xf4/0x178
  |   driver_attach+0x3c/0x58
  |   bus_add_driver+0x234/0x4d4
  |   driver_register+0xf4/0x3c0
  |   __platform_driver_register+0x60/0x88
  |   scmi_driver_init+0xb0/0x104
  |   do_one_initcall+0xb4/0x664
  |   kernel_init_freeable+0x3c8/0x894
  |   kernel_init+0x24/0x1e8
  |   ret_from_fork+0x10/0x20

Fixes: ee7a9c9 ("firmware: arm_scmi: Add support for multiple device per protocol")
Signed-off-by: Xinqi Zhang <[email protected]>
Reviewed-by: Cristian Marussi <[email protected]>
Reviewed-by: Bjorn Andersson <[email protected]>
Message-Id: <20241016-fix-arm-scmi-slab-use-after-free-v2-1-1783685ef90d@quicinc.com>
Signed-off-by: Sudeep Holla <[email protected]>

drivers/firmware/arm_scmi/bus.c

@@ -325,7 +325,10 @@ EXPORT_SYMBOL_GPL(scmi_driver_unregister);
 
 static void scmi_device_release(struct device *dev)
 {
-	kfree(to_scmi_dev(dev));
+	struct scmi_device *scmi_dev = to_scmi_dev(dev);
+
+	kfree_const(scmi_dev->name);
+	kfree(scmi_dev);
 }
 
 static void __scmi_device_destroy(struct scmi_device *scmi_dev)
@@ -338,7 +341,6 @@ static void __scmi_device_destroy(struct scmi_device *scmi_dev)
 	if (scmi_dev->protocol_id == SCMI_PROTOCOL_SYSTEM)
 		atomic_set(&scmi_syspower_registered, 0);
 
-	kfree_const(scmi_dev->name);
 	ida_free(&scmi_bus_id, scmi_dev->id);
 	device_unregister(&scmi_dev->dev);
 }
@@ -410,7 +412,6 @@ __scmi_device_create(struct device_node *np, struct device *parent,
 
 	return scmi_dev;
 put_dev:
-	kfree_const(scmi_dev->name);
 	put_device(&scmi_dev->dev);
 	ida_free(&scmi_bus_id, id);
 	return NULL;