Commits
Krzysztof Kozlowski committed a0ee2ac039c
pinctrl: samsung: Suppress unbinding to prevent theoretical attacks
Although unbinding a pinctrl driver requires root privileges but it
still might be used theoretically in certain attacks (by triggering NULL
pointer exception or memory corruption).
Samsung pincontrol drivers are essential for system operation so their
removal is not expected. They do not implement remove() driver callback
and they are not buildable as modules.
Suppression of the unbinding will prevent triggering NULL pointer
exception like this (Odroid XU3):
$ echo 13400000.pinctrl > /sys/bus/platform/drivers/samsung-pinctrl/unbind
$ cat /sys/kernel/debug/gpio
Unable to handle kernel NULL pointer dereference at virtual address 00000c44
pgd = ec41c000
[00000c44] *pgd=6d448835, *pte=00000000, *ppte=00000000
Internal error: Oops: 17 [#1] PREEMPT SMP ARM
(samsung_gpio_get) from [<c034f9a0>] (gpiolib_seq_show+0x1b0/0x26c)
(gpiolib_seq_show) from [<c01fb8c0>] (seq_read+0x304/0x4b8)
(seq_read) from [<c02dbc78>] (full_proxy_read+0x4c/0x64)
(full_proxy_read) from [<c01d9fb0>] (__vfs_read+0x2c/0x110)
(__vfs_read) from [<c01db400>] (vfs_read+0x8c/0x110)
(vfs_read) from [<c01db4c4>] (SyS_read+0x40/0x8c)
(SyS_read) from [<c01078c0>] (ret_fast_syscall+0x0/0x3c)
Suggested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>