[PATCH] clk: fix slab-use-after-free when clk_core_populate_parent_map failed

[Yun Zhou]

If clk_core_populate_parent_map() fails, core->parents will be immediately
released within clk_core_populate_parent_map(). Therefore it is can't be
released in __clk_release() again.

This fixes the following KASAN reported issue:

==================================================================
BUG: KASAN: slab-use-after-free in __clk_release+0x80/0x160
Read of size 8 at addr ffffff8043fd0980 by task kworker/u6:0/27

CPU: 1 PID: 27 Comm: kworker/u6:0 Tainted: G        W          6.6.69-yocto-standard+ #7
Hardware name: Raspberry Pi 4 Model B (DT)
Workqueue: events_unbound deferred_probe_work_func
Call trace:
 dump_backtrace+0x98/0xf8
 show_stack+0x20/0x38
 dump_stack_lvl+0x48/0x60
 print_report+0xf8/0x5d8
 kasan_report+0xb4/0x100
 __asan_load8+0x9c/0xc0
 __clk_release+0x80/0x160
 __clk_register+0x6dc/0xfb8
 devm_clk_hw_register+0x70/0x108
 bcm2835_register_clock+0x284/0x358
 bcm2835_clk_probe+0x2c4/0x438
 platform_probe+0x98/0x110
 really_probe+0x1e4/0x3e8
 __driver_probe_device+0xc0/0x1a0
 driver_probe_device+0x110/0x1e8
 __device_attach_driver+0xf0/0x1a8
 bus_for_each_drv+0xf8/0x178
 __device_attach+0x120/0x240
 device_initial_probe+0x1c/0x30
 bus_probe_device+0xdc/0xe8
 deferred_probe_work_func+0xe8/0x130
 process_one_work+0x2a4/0x698
 worker_thread+0x53c/0x708
 kthread+0x1b4/0x1c8
 ret_from_fork+0x10/0x20

Allocated by task 27:
 kasan_save_stack+0x3c/0x68
 kasan_set_track+0x2c/0x40
 kasan_save_alloc_info+0x24/0x38
 __kasan_kmalloc+0xd4/0xd8
 __kmalloc+0x74/0x238
 __clk_register+0x718/0xfb8
 devm_clk_hw_register+0x70/0x108
 bcm2835_register_clock+0x284/0x358
 bcm2835_clk_probe+0x2c4/0x438
 platform_probe+0x98/0x110
 really_probe+0x1e4/0x3e8
 __driver_probe_device+0xc0/0x1a0
 driver_probe_device+0x110/0x1e8
 __device_attach_driver+0xf0/0x1a8
 bus_for_each_drv+0xf8/0x178
 __device_attach+0x120/0x240
 device_initial_probe+0x1c/0x30
 bus_probe_device+0xdc/0xe8
 deferred_probe_work_func+0xe8/0x130
 process_one_work+0x2a4/0x698
 worker_thread+0x53c/0x708
 kthread+0x1b4/0x1c8
 ret_from_fork+0x10/0x20

Freed by task 27:
 kasan_save_stack+0x3c/0x68
 kasan_set_track+0x2c/0x40
 kasan_save_free_info+0x38/0x60
 __kasan_slab_free+0x100/0x170
 slab_free_freelist_hook+0xcc/0x218
 __kmem_cache_free+0x158/0x210
 kfree+0x88/0x140
 __clk_register+0x9d0/0xfb8
 devm_clk_hw_register+0x70/0x108
 bcm2835_register_clock+0x284/0x358
 bcm2835_clk_probe+0x2c4/0x438
 platform_probe+0x98/0x110
 really_probe+0x1e4/0x3e8
 __driver_probe_device+0xc0/0x1a0
 driver_probe_device+0x110/0x1e8
 __device_attach_driver+0xf0/0x1a8
 bus_for_each_drv+0xf8/0x178
 __device_attach+0x120/0x240
 device_initial_probe+0x1c/0x30
 bus_probe_device+0xdc/0xe8
 deferred_probe_work_func+0xe8/0x130
 process_one_work+0x2a4/0x698
 worker_thread+0x53c/0x708
 kthread+0x1b4/0x1c8
 ret_from_fork+0x10/0x20

The buggy address belongs to the object at ffffff8043fd0800
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 384 bytes inside of
 freed 512-byte region [ffffff8043fd0800, ffffff8043fd0a00)

The buggy address belongs to the physical page:
page:fffffffe010ff400 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffffff8043fd0e00 pfn:0x43fd0
head:fffffffe010ff400 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x4000000000000840(slab|head|zone=1)
page_type: 0xffffffff()
raw: 4000000000000840 ffffff8040002f40 ffffff8040000a50 ffffff8040000a50
raw: ffffff8043fd0e00 0000000000150002 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffffff8043fd0880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffffff8043fd0900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffffff8043fd0980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffffff8043fd0a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffffff8043fd0a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Fixes: 9d05ae531c2c ("clk: Initialize struct clk_core kref earlier")
Signed-off-by: Yun Zhou <yun.zhou@xxxxxxxxxxxxx>
---
 drivers/clk/clk.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 0565c87656cf..3f89ed51d4a4 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -4242,7 +4242,6 @@ static int clk_core_populate_parent_map(struct clk_core *core,
 	 * having a cache of names/clk_hw pointers to clk_core pointers.
 	 */
 	parents = kcalloc(num_parents, sizeof(*parents), GFP_KERNEL);
-	core->parents = parents;
 	if (!parents)
 		return -ENOMEM;
 
@@ -4283,6 +4282,8 @@ static int clk_core_populate_parent_map(struct clk_core *core,
 		}
 	}
 
+	core->parents = parents;
+
 	return 0;
 }
 
@@ -4290,7 +4291,7 @@ static void clk_core_free_parent_map(struct clk_core *core)
 {
 	int i = core->num_parents;
 
-	if (!core->num_parents)
+	if (!core->parents)
 		return;
 
 	while (--i >= 0) {
-- 
2.27.0