regulator: da9121: Fix uninit-value in da9121_assign_chip_model()

In the Linux kernel, the following vulnerability has been resolved:

regulator: da9121: Fix uninit-value in da9121_assign_chip_model()

KASAN report slab-out-of-bounds in __regmap_init as follows:

BUG: KASAN: slab-out-of-bounds in __regmap_init drivers/base/regmap/regmap.c:841

Read of size 1 at addr ffff88803678cdf1 by task xrun/9137

CPU: 0 PID: 9137 Comm: xrun Tainted: G W 5.18.0-rc2

Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014

Call Trace:

<TASK>

dump_stack_lvl+0xe8/0x15a lib/dump_stack.c:88

print_report.cold+0xcd/0x69b mm/kasan/report.c:313

kasan_report+0x8e/0xc0 mm/kasan/report.c:491

__regmap_init+0x4540/0x4ba0 drivers/base/regmap/regmap.c:841

__devm_regmap_init+0x7a/0x100 drivers/base/regmap/regmap.c:1266

__devm_regmap_init_i2c+0x65/0x80 drivers/base/regmap/regmap-i2c.c:394

da9121_i2c_probe+0x386/0x6d1 drivers/regulator/da9121-regulator.c:1039

i2c_device_probe+0x959/0xac0 drivers/i2c/i2c-core-base.c:563

This happend when da9121 device is probe by da9121_i2c_id, but with

invalid dts. Thus, chip->subvariant_id is set to -EINVAL, and later

da9121_assign_chip_model() will access 'regmap' without init it.

Fix it by return -EINVAL from da9121_assign_chip_model() if

'chip->subvariant_id' is invalid.