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Date: Thu, 16 Oct 2008 16:17:18 -0700 From: Andrew Morton <akpm@...ux-foundation.org> To: David Brownell <david-b@...bell.net> Cc: avorontsov@...mvista.com, linux-kernel@...r.kernel.org, stable@...nel.org Subject: Re: [patch] gpiolib: fix oops in gpio_get_value_cansleep() On Thu, 16 Oct 2008 08:45:22 -0700 David Brownell <david-b@...bell.net> wrote: > From: David Brownell <dbrownell@...rs.sourceforge.net> > > We can get the following oops from gpio_get_value_cansleep() > when a GPIO controller doesn't provide a get() callback: We can, but do we? ;) iow: is this needed in any -stable release? > 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@...mvista.com> > Signed-off-by: David Brownell <dbrownell@...rs.sourceforge.net> > --- > drivers/gpio/gpiolib.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > --- a/drivers/gpio/gpiolib.c > +++ b/drivers/gpio/gpiolib.c > @@ -1056,7 +1056,7 @@ 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); > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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