Re: [PATCH 1/4] gpio: Assign gpio_irq_chip::parents to non-stack pointer

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

On Mon, Oct 8, 2018 at 6:32 PM Stephen Boyd <swboyd@xxxxxxxxxxxx> wrote:

> gpiochip_set_cascaded_irqchip() is passed 'parent_irq' as an argument
> and then the address of that argument is assigned to the gpio chips
> gpio_irq_chip 'parents' pointer shortly thereafter. This can't ever
> work, because we've just assigned some stack address to a pointer that
> we plan to dereference later in gpiochip_irq_map(). I ran into this
> issue with the KASAN report below when gpiochip_irq_map() tried to setup
> the parent irq with a total junk pointer for the 'parents' array.
>
> BUG: KASAN: stack-out-of-bounds in gpiochip_irq_map+0x228/0x248
> Read of size 4 at addr ffffffc0dde472e0 by task swapper/0/1
>
> CPU: 7 PID: 1 Comm: swapper/0 Not tainted 4.14.72 #34
> Call trace:
> [<ffffff9008093638>] dump_backtrace+0x0/0x718
> [<ffffff9008093da4>] show_stack+0x20/0x2c
> [<ffffff90096b9224>] __dump_stack+0x20/0x28
> [<ffffff90096b91c8>] dump_stack+0x80/0xbc
> [<ffffff900845a350>] print_address_description+0x70/0x238
> [<ffffff900845a8e4>] kasan_report+0x1cc/0x260
> [<ffffff900845aa14>] __asan_report_load4_noabort+0x2c/0x38
> [<ffffff900897e098>] gpiochip_irq_map+0x228/0x248
> [<ffffff900820cc08>] irq_domain_associate+0x114/0x2ec
> [<ffffff900820d13c>] irq_create_mapping+0x120/0x234
> [<ffffff900820da78>] irq_create_fwspec_mapping+0x4c8/0x88c
> [<ffffff900820e2d8>] irq_create_of_mapping+0x180/0x210
> [<ffffff900917114c>] of_irq_get+0x138/0x198
> [<ffffff9008dc70ac>] spi_drv_probe+0x94/0x178
> [<ffffff9008ca5168>] driver_probe_device+0x51c/0x824
> [<ffffff9008ca6538>] __device_attach_driver+0x148/0x20c
> [<ffffff9008ca14cc>] bus_for_each_drv+0x120/0x188
> [<ffffff9008ca570c>] __device_attach+0x19c/0x2dc
> [<ffffff9008ca586c>] device_initial_probe+0x20/0x2c
> [<ffffff9008ca18bc>] bus_probe_device+0x80/0x154
> [<ffffff9008c9b9b4>] device_add+0x9b8/0xbdc
> [<ffffff9008dc7640>] spi_add_device+0x1b8/0x380
> [<ffffff9008dcbaf0>] spi_register_controller+0x111c/0x1378
> [<ffffff9008dd6b10>] spi_geni_probe+0x4dc/0x6f8
> [<ffffff9008cab058>] platform_drv_probe+0xdc/0x130
> [<ffffff9008ca5168>] driver_probe_device+0x51c/0x824
> [<ffffff9008ca59cc>] __driver_attach+0x100/0x194
> [<ffffff9008ca0ea8>] bus_for_each_dev+0x104/0x16c
> [<ffffff9008ca58c0>] driver_attach+0x48/0x54
> [<ffffff9008ca1edc>] bus_add_driver+0x274/0x498
> [<ffffff9008ca8448>] driver_register+0x1ac/0x230
> [<ffffff9008caaf6c>] __platform_driver_register+0xcc/0xdc
> [<ffffff9009c4b33c>] spi_geni_driver_init+0x1c/0x24
> [<ffffff9008084cb8>] do_one_initcall+0x240/0x3dc
> [<ffffff9009c017d0>] kernel_init_freeable+0x378/0x468
> [<ffffff90096e8240>] kernel_init+0x14/0x110
> [<ffffff9008086fcc>] ret_from_fork+0x10/0x18
>
> The buggy address belongs to the page:
> page:ffffffbf037791c0 count:0 mapcount:0 mapping:          (null) index:0x0
> flags: 0x4000000000000000()
> raw: 4000000000000000 0000000000000000 0000000000000000 00000000ffffffff
> raw: ffffffbf037791e0 ffffffbf037791e0 0000000000000000 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>  ffffffc0dde47180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>  ffffffc0dde47200: f1 f1 f1 f1 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f2 f2
> >ffffffc0dde47280: f2 f2 00 00 00 00 00 00 00 00 00 00 f3 f3 f3 f3
>                                                        ^
>  ffffffc0dde47300: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>  ffffffc0dde47380: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>
> Let's leave around one unsigned int in the gpio_irq_chip struct for the
> single parent irq case and repoint the 'parents' array at it. This way
> code is left mostly intact to setup parents and we waste an extra few
> bytes per structure of which there should be only a handful in a system.
>
> Cc: Evan Green <evgreen@xxxxxxxxxxxx>
> Cc: Thierry Reding <treding@xxxxxxxxxx>
> Cc: Grygorii Strashko <grygorii.strashko@xxxxxx>
> Fixes: e0d897289813 ("gpio: Implement tighter IRQ chip integration")
> Signed-off-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>

OMG critical fix. I fixed up the thing the kbuild robot was complaining
about with some vanilla kerneldoc and applied for fixes since it's kind
of urgent.

Please check the result.

Yours,
Linus Walleij