• David Brownell's avatar
    gpiolib: fix oops in gpio_get_value_cansleep() · 978ccaa8
    David Brownell authored
    We can get the following oops from gpio_get_value_cansleep() when a GPIO
    controller doesn't provide a get() callback:
    
     Unable to handle kernel paging request for instruction fetch
     Faulting instruction address: 0x00000000
     Oops: Kernel access of bad area, sig: 11 [#1]
     [...]
     NIP [00000000] 0x0
     LR [c0182fb0] gpio_get_value_cansleep+0x40/0x50
     Call Trace:
     [c7b79e80] [c0183f28] gpio_value_show+0x5c/0x94
     [c7b79ea0] [c01a584c] dev_attr_show+0x30/0x7c
     [c7b79eb0] [c00d6b48] fill_read_buffer+0x68/0xe0
     [c7b79ed0] [c00d6c54] sysfs_read_file+0x94/0xbc
     [c7b79ef0] [c008f24c] vfs_read+0xb4/0x16c
     [c7b79f10] [c008f580] sys_read+0x4c/0x90
     [c7b79f40] [c0013a14] ret_from_syscall+0x0/0x38
    
    It's OK to request the value of *any* GPIO; most GPIOs are bidirectional,
    so configuring them as outputs just enables an output driver and doesn't
    disable the input logic.
    
    So the problem is that gpio_get_value_cansleep() isn't making the same
    sanity check that gpio_get_value() does: making sure this GPIO isn't one
    of the atypical "no input logic" cases.
    Reported-by: default avatarAnton Vorontsov <avorontsov@ru.mvista.com>
    Signed-off-by: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
    Cc: <stable@kernel.org>		[2.6.27.x, 2.6.26.x, 2.6.25.x]
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    978ccaa8
gpiolib.c 30.9 KB