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gpio: virtuser: skip free_irq when no IRQ is installed

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Disabling interrupt monitoring uses atomic_xchg() to clear the stored IRQ.
When monitoring is already disabled, atomic_xchg() returns 0. It must not
be passed to free_irq().

The bug is reproducible on an x86_64 QEMU guest with
CONFIG_GPIO_VIRTUSER=y and CONFIG_GPIO_SIM=y. Configure a live
gpio-virtuser device through configfs. Its input lookup must refer to a
live gpio-sim bank, such as key gpio-sim-test with offset 0. The
consumer's dev_name attribute is shown as <dev> below; then run:

    echo 0 > /sys/kernel/debug/gpio-virtuser/<dev>/gpiod:input:0/interrupts

On an unpatched kernel, this reaches gpio_virtuser_interrupts_set() with
ld->irq still at its initial value 0, and free_irq() reports:

    Trying to free already-free IRQ 0

The same reproducer completes without the warning on the patched kernel.

Fixes: 91581c4b3f ("gpio: virtuser: new virtual testing driver for the GPIO API")
Assisted-by: LLM
Signed-off-by: Runyu Xiao <runyu.xiao@seu.edu.cn>
Reviewed-by: Linus Walleij <linusw@kernel.org>
Link: https://patch.msgid.link/20260914051537.15320-1-runyu.xiao@seu.edu.cn
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
This commit is contained in:
Runyu Xiao 2026-09-14 13:15:37 +08:00 • committed by Bartosz Golaszewski
commit 50fd0ada8d
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