Messages in this thread Patch in this message | | | Date | Fri, 7 Nov 2008 15:25:59 -0800 | From | Greg KH <> | Subject | [patch 01/16] gpiolib: fix oops in gpio_get_value_cansleep() |
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2.6.25-stable review patch. If anyone has any objections, please let us know.
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From: David Brownell <dbrownell@users.sourceforge.net>
commit 978ccaa8ea5d8c7bf6b676209f2fc126eae6355b upstream
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: Anton Vorontsov <avorontsov@ru.mvista.com> Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- drivers/gpio/gpiolib.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -426,7 +426,7 @@ int gpio_get_value_cansleep(unsigned gpi might_sleep_if(extra_checks); chip = gpio_to_chip(gpio); - return chip->get(chip, gpio - chip->base); + return chip->get ? chip->get(chip, gpio - chip->base) : 0; } EXPORT_SYMBOL_GPL(gpio_get_value_cansleep); --
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