[PATCH 2/2] HID: intel-thc-hid: intel-thc: Fix incorrect pointer arithmetic in I2C regs save

[Aaron Ma <aaron.ma@canonical.com>]

Improper use of secondary pointer (&dev->i2c_subip_regs) caused
kernel crash and out-of-bounds error:

 BUG: KASAN: slab-out-of-bounds in _regmap_bulk_read+0x449/0x510
 Write of size 4 at addr ffff888136005dc0 by task kworker/u33:5/5107

 CPU: 3 UID: 0 PID: 5107 Comm: kworker/u33:5 Not tainted 6.16.0+ #3 PREEMPT(voluntary)
 Workqueue: async async_run_entry_fn
 Call Trace:
  <TASK>
  dump_stack_lvl+0x76/0xa0
  print_report+0xd1/0x660
  ? __pfx__raw_spin_lock_irqsave+0x10/0x10
  ? kasan_complete_mode_report_info+0x26/0x200
  kasan_report+0xe1/0x120
  ? _regmap_bulk_read+0x449/0x510
  ? _regmap_bulk_read+0x449/0x510
  __asan_report_store4_noabort+0x17/0x30
  _regmap_bulk_read+0x449/0x510
  ? __pfx__regmap_bulk_read+0x10/0x10
  regmap_bulk_read+0x270/0x3d0
  pio_complete+0x1ee/0x2c0 [intel_thc]
  ? __pfx_pio_complete+0x10/0x10 [intel_thc]
  ? __pfx_pio_wait+0x10/0x10 [intel_thc]
  ? regmap_update_bits_base+0x13b/0x1f0
  thc_i2c_subip_pio_read+0x117/0x270 [intel_thc]
  thc_i2c_subip_regs_save+0xc2/0x140 [intel_thc]
  ? __pfx_thc_i2c_subip_regs_save+0x10/0x10 [intel_thc]
[...]
 The buggy address belongs to the object at ffff888136005d00
  which belongs to the cache kmalloc-rnd-12-192 of size 192
 The buggy address is located 0 bytes to the right of
  allocated 192-byte region [ffff888136005d00, ffff888136005dc0)

Replaced with direct array indexing (&dev->i2c_subip_regs[i]) to ensure
safe memory access.

Fixes: 4228966def884 ("HID: intel-thc-hid: intel-thc: Add THC I2C config interfaces")
Signed-off-by: Aaron Ma <aaron.ma@canonical.com>
---
 drivers/hid/intel-thc-hid/intel-thc/intel-thc-dev.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/intel-thc-hid/intel-thc/intel-thc-dev.c b/drivers/hid/intel-thc-hid/intel-thc/intel-thc-dev.c
index c105df7f6c873..4698722e0d0a6 100644
--- a/drivers/hid/intel-thc-hid/intel-thc/intel-thc-dev.c
+++ b/drivers/hid/intel-thc-hid/intel-thc/intel-thc-dev.c
@@ -1539,7 +1539,7 @@ int thc_i2c_subip_regs_save(struct thc_device *dev)
 
 	for (int i = 0; i < ARRAY_SIZE(i2c_subip_regs); i++) {
 		ret = thc_i2c_subip_pio_read(dev, i2c_subip_regs[i],
-					     &read_size, (u32 *)&dev->i2c_subip_regs + i);
+					     &read_size, &dev->i2c_subip_regs[i]);
 		if (ret < 0)
 			return ret;
 	}
@@ -1562,7 +1562,7 @@ int thc_i2c_subip_regs_restore(struct thc_device *dev)
 
 	for (int i = 0; i < ARRAY_SIZE(i2c_subip_regs); i++) {
 		ret = thc_i2c_subip_pio_write(dev, i2c_subip_regs[i],
-					      write_size, (u32 *)&dev->i2c_subip_regs + i);
+					      write_size, &dev->i2c_subip_regs[i]);
 		if (ret < 0)
 			return ret;
 	}
-- 
2.43.0