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SubjectPossible race in xilinx-xadc.ko
Date
Hello.

While searching for races in the Linux kernel I've come across
"drivers/iio/adc/xilinx-xadc.ko" module. Here is a question that I came
up with while analyzing results. Lines are given using the info from
Linux v4.12.

Consider the following case:

Thread 1: Thread 2:
xadc_probe
iio_triggered_buffer_setup
xadc_trigger_handler
->xadc_read_adc_reg
->_xadc_read_adc_reg
->xadc_zynq_read_adc_reg
->xadc_zynq_setup ->xadc_zynq_update_intmsk
xadc->zynq_intmask = ~0 xadc->zynq_intmask &= ~mask
(xilinx-xadc-core.c: line 340) (xilinx-xadc-core.c: line 152)
xadc_write_reg(xadc->zynq_intmask) xadc_write_reg(xadc->zynq_intmask)

Judging by the comments to iio_triggered_buffer_setup() the best
practice is to call it after the indio_dev structure had been fully
initialized. In the suggested case xadc_trigger_handler() interferes in
the initialization process. Both xadc_zynq_setup() and
xadc_zynq_update_intmsk() will write the same xadc->zynq_intmask though
it should probably be different. Is this race feasible from your point
of view?

Thank you for your time.

-- Anton Volkov
Linux Verification Center, ISPRAS
web: http://linuxtesting.org
e-mail: avolkov@ispras.ru

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