The H6 main pin controller has four banks of interrupt-triggering pins.
The driver as originally submitted only specified three, but had pin
descriptions referencing a fourth bank. This results in a out-of-bounds
access into .irq_array of struct sunxi_pinctrl. This however did not
result in a crash until v4.20, with commit a66d9724 ("devres: Align
data[] to ARCH_KMALLOC_MINALIGN"), which changed the alignment of memory
region returned by devm_kcalloc(). The increase likely moved the
out-of-bounds access into the next, unmapped page.

With KASAN on, the bug is quite clear:

    BUG: KASAN: slab-out-of-bounds in sunxi_pinctrl_init_with_variant+0x49c/0x12b8
    Write of size 4 at addr ffff80002c680280 by task swapper/0/1

    CPU: 2 PID: 1 Comm: swapper/0 Not tainted 5.0.0-rc1-00016-gc480a5e6a077 #3
    Hardware name: OrangePi Lite2 (DT)
    Call trace:
     dump_backtrace+0x0/0x220
     show_stack+0x14/0x20
     dump_stack+0xac/0xd4
     print_address_description+0x60/0x25c
     kasan_report+0x14c/0x1ac
     __asan_store4+0x80/0xa0
     sunxi_pinctrl_init_with_variant+0x49c/0x12b8
     h6_pinctrl_probe+0x18/0x20
     platform_drv_probe+0x6c/0xc8
     really_probe+0x244/0x4b0
     driver_probe_device.part.4+0x11c/0x164
     __driver_attach+0x120/0x190
     bus_for_each_dev+0xe8/0x158
     driver_attach+0x30/0x40
     bus_add_driver+0x308/0x318
     driver_register+0xbc/0x1d0
     __platform_driver_register+0x7c/0x88
     h6_pinctrl_driver_init+0x18/0x20
     do_one_initcall+0xd4/0x208
     kernel_init_freeable+0x230/0x2c8
     kernel_init+0x10/0x108
     ret_from_fork+0x10/0x1c

    Allocated by task 1:
     kasan_kmalloc.part.0+0x4c/0x100
     kasan_kmalloc+0xc4/0xe8
     kasan_slab_alloc+0x14/0x20
     __kmalloc_track_caller+0x130/0x238
     devm_kmalloc+0x34/0xd0
     sunxi_pinctrl_init_with_variant+0x1d8/0x12b8
     h6_pinctrl_probe+0x18/0x20
     platform_drv_probe+0x6c/0xc8
     really_probe+0x244/0x4b0
     driver_probe_device.part.4+0x11c/0x164
     __driver_attach+0x120/0x190
     bus_for_each_dev+0xe8/0x158
     driver_attach+0x30/0x40
     bus_add_driver+0x308/0x318
     driver_register+0xbc/0x1d0
     __platform_driver_register+0x7c/0x88
     h6_pinctrl_driver_init+0x18/0x20
     do_one_initcall+0xd4/0x208
     kernel_init_freeable+0x230/0x2c8
     kernel_init+0x10/0x108
     ret_from_fork+0x10/0x1c

    Freed by task 0:
    (stack is not available)

    The buggy address belongs to the object at ffff80002c680080
     which belongs to the cache kmalloc-512 of size 512
    The buggy address is located 0 bytes to the right of
     512-byte region [ffff80002c680080, ffff80002c680280)
    The buggy address belongs to the page:
    page:ffff7e0000b1a000 count:1 mapcount:0 mapping:ffff80002e00c780 index:0xffff80002c683c80 compound_mapcount: 0
    flags: 0x10200(slab|head)
    raw: 0000000000010200 ffff80002e003a10 ffff80002e003a10 ffff80002e00c780
    raw: ffff80002c683c80 0000000000100001 00000001ffffffff 0000000000000000
    page dumped because: kasan: bad access detected

    Memory state around the buggy address:
     ffff80002c680180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
     ffff80002c680200: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
    >ffff80002c680280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
		       ^
     ffff80002c680300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
     ffff80002c680380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc

Correct the number of IRQ banks so there are no more mismatches.

Fixes: c8a83090 ("pinctrl: sunxi: add support for the Allwinner H6 main pin controller")
Cc: <stable@vger.kernel.org>
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Tested-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>