From 978ccaa8ea5d8c7bf6b676209f2fc126eae6355b Mon Sep 17 00:00:00 2001 From: David Brownell Date: Sat, 18 Oct 2008 20:27:49 -0700 Subject: [PATCH] gpiolib: fix oops in gpio_get_value_cansleep() 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 Signed-off-by: David Brownell Cc: [2.6.27.x, 2.6.26.x, 2.6.25.x] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/gpio/gpiolib.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index 70de72c443e..22edc4273ef 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -1105,7 +1105,7 @@ int gpio_get_value_cansleep(unsigned gpio) 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); -- 2.41.0