• Krzysztof Kozlowski's avatar
    pinctrl: samsung: Suppress unbinding to prevent theoretical attacks · a0ee2ac0
    Krzysztof Kozlowski authored
    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: default avatarMarek Szyprowski <m.szyprowski@samsung.com>
    Signed-off-by: default avatarKrzysztof Kozlowski <k.kozlowski@samsung.com>
    Reviewed-by: default avatarJavier Martinez Canillas <javier@osg.samsung.com>
    Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
    a0ee2ac0
pinctrl-exynos5440.c 27.3 KB