• Lars-Peter Clausen's avatar
    iio: adis_lib: Initialize trigger before requesting interrupt · 6315213f
    Lars-Peter Clausen authored
    commit f027e0b3 upstream.
    
    The adis_probe_trigger() creates a new IIO trigger and requests an
    interrupt associated with the trigger. The interrupt uses the generic
    iio_trigger_generic_data_rdy_poll() function as its interrupt handler.
    
    Currently the driver initializes some fields of the trigger structure after
    the interrupt has been requested. But an interrupt can fire as soon as it
    has been requested. This opens up a race condition.
    
    iio_trigger_generic_data_rdy_poll() will access the trigger data structure
    and dereference the ops field. If the ops field is not yet initialized this
    will result in a NULL pointer deref.
    
    It is not expected that the device generates an interrupt at this point, so
    typically this issue did not surface unless e.g. due to a hardware
    misconfiguration (wrong interrupt number, wrong polarity, etc.).
    
    But some newer devices from the ADIS family start to generate periodic
    interrupts in their power-on reset configuration and unfortunately the
    interrupt can not be masked in the device.  This makes the race condition
    much more visible and the following crash has been observed occasionally
    when booting a system using the ADIS16460.
    
    	Unable to handle kernel NULL pointer dereference at virtual address 00000008
    	pgd = c0004000
    	[00000008] *pgd=00000000
    	Internal error: Oops: 5 [#1] PREEMPT SMP ARM
    	Modules linked in:
    	CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.9.0-04126-gf9739f0-dirty #257
    	Hardware name: Xilinx Zynq Platform
    	task: ef04f640 task.stack: ef050000
    	PC is at iio_trigger_notify_done+0x30/0x68
    	LR is at iio_trigger_generic_data_rdy_poll+0x18/0x20
    	pc : [<c042d868>]    lr : [<c042d924>]    psr: 60000193
    	sp : ef051bb8  ip : 00000000  fp : ef106400
    	r10: c081d80a  r9 : ef3bfa00  r8 : 00000087
    	r7 : ef051bec  r6 : 00000000  r5 : ef3bfa00  r4 : ee92ab00
    	r3 : 00000000  r2 : 00000000  r1 : 00000000  r0 : ee97e400
    	Flags: nZCv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment none
    	Control: 18c5387d  Table: 0000404a  DAC: 00000051
    	Process swapper/0 (pid: 1, stack limit = 0xef050210)
    	[<c042d868>] (iio_trigger_notify_done) from [<c0065b10>] (__handle_irq_event_percpu+0x88/0x118)
    	[<c0065b10>] (__handle_irq_event_percpu) from [<c0065bbc>] (handle_irq_event_percpu+0x1c/0x58)
    	[<c0065bbc>] (handle_irq_event_percpu) from [<c0065c30>] (handle_irq_event+0x38/0x5c)
    	[<c0065c30>] (handle_irq_event) from [<c0068e28>] (handle_level_irq+0xa4/0x130)
    	[<c0068e28>] (handle_level_irq) from [<c0064e74>] (generic_handle_irq+0x24/0x34)
    	[<c0064e74>] (generic_handle_irq) from [<c021ab7c>] (zynq_gpio_irqhandler+0xb8/0x13c)
    	[<c021ab7c>] (zynq_gpio_irqhandler) from [<c0064e74>] (generic_handle_irq+0x24/0x34)
    	[<c0064e74>] (generic_handle_irq) from [<c0065370>] (__handle_domain_irq+0x5c/0xb4)
    	[<c0065370>] (__handle_domain_irq) from [<c000940c>] (gic_handle_irq+0x48/0x8c)
    	[<c000940c>] (gic_handle_irq) from [<c0013e8c>] (__irq_svc+0x6c/0xa8)
    
    To fix this make sure that the trigger is fully initialized before
    requesting the interrupt.
    
    Fixes: ccd2b52f ("staging:iio: Add common ADIS library")
    Reported-by: default avatarRobin Getz <Robin.Getz@analog.com>
    Signed-off-by: default avatarLars-Peter Clausen <lars@metafoo.de>
    Cc: <Stable@vger.kernel.org>
    Signed-off-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    6315213f
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