* Re: [PATCH v4 06/15] media: sunxi-cir: Ensure no more interrupts can occur before free
2026-07-27 13:18 ` [PATCH v4 06/15] media: sunxi-cir: Ensure no more interrupts can occur before free Sean Young
@ 2026-07-27 14:40 ` sashiko-bot
0 siblings, 0 replies; 2+ messages in thread
From: sashiko-bot @ 2026-07-27 14:40 UTC (permalink / raw)
To: Sean Young; +Cc: linux-sunxi, media-ci
Thank you for your contribution! Sashiko AI review found 3 potential issue(s) to consider:
Pre-existing issues:
- [High] The patch attempts to fix a use-after-free by delaying `rc_free_device()` until after `sunxi_ir_hw_exit()`. However, `sunxi_ir_hw_exit()` only disables the hardware clocks and asserts reset; it does not mask the devm-managed IRQ or wait for in-flight interrupt handlers to complete via `synchronize_irq()`. This leaves the driver vulnerable to two fatal issues: 1) If an IRQ handler is executing concurrently, disabling the APB clock while it accesses memory-mapped registers will cause a synchronous external abort (bus hang). 2) If the handler continues executing after `sunxi_ir_hw_exit()` returns, it will access `ir->rc` while it is being freed by `rc_free_device()`, resulting in a use-after-free.
- [High] The IRQ is requested via `devm_request_irq()` before the hardware clocks are initialized by `sunxi_ir_hw_init()`, risking a synchronous external abort (bus hang) on spurious or pending interrupts during probe.
- [High] The devm-managed IRQ handler can execute and access a freed RC device if `sunxi_ir_hw_init()` fails in `sunxi_ir_probe()`.
--
--- Patch [6]: [PATCH v4 06/15] media: sunxi-cir: Ensure no more interrupts can occur before free ---
commit 6e49e6c93b7dee54eb10aca37f27b9448afeb67a
Author: Sean Young <sean@mess.org>
media: sunxi-cir: Ensure no more interrupts can occur before free
Only call rc_free_device() once the hardware has been stopped.
Fixes: dccc0c3ddf8f ("media: rc: fix race between unregister and urb/irq callbacks")
Cc: stable@vger.kernel.org
> diff --git a/drivers/media/rc/sunxi-cir.c b/drivers/media/rc/sunxi-cir.c
> index 28e840a7e5b8c..af1ee08ffdbec 100644
> --- a/drivers/media/rc/sunxi-cir.c
> +++ b/drivers/media/rc/sunxi-cir.c
> @@ -374,8 +374,8 @@ static void sunxi_ir_remove(struct platform_device *pdev)
> struct sunxi_ir *ir = platform_get_drvdata(pdev);
>
> rc_unregister_device(ir->rc);
> - rc_free_device(ir->rc);
> sunxi_ir_hw_exit(&pdev->dev);
> + rc_free_device(ir->rc);
[Severity: High]
This is a pre-existing issue, but does sunxi_ir_hw_exit() adequately prevent
further interrupts from executing?
sunxi_ir_hw_exit() disables clocks and asserts reset, but it doesn't appear
to mask the devm-managed IRQ or wait for in-flight handlers to finish via
synchronize_irq().
If an interrupt fires concurrently or an IRQ handler is already running:
drivers/media/rc/sunxi-cir.c:sunxi_ir_irq() {
...
status = readl(ir->base + SUNXI_IR_RXSTA_REG);
...
}
Could disabling the APB clock while this handler is accessing memory-mapped
registers cause a synchronous external abort? Furthermore, if the handler
continues executing after sunxi_ir_hw_exit() returns, could it access the
freed ir->rc device pointer?
> }
Looking at the probe function in the same file:
drivers/media/rc/sunxi-cir.c:sunxi_ir_probe() {
...
ret = devm_request_irq(dev, ir->irq, sunxi_ir_irq, 0, SUNXI_IR_DEV, ir);
if (ret) {
dev_err(dev, "failed request irq\n");
goto exit_unregister_dev;
}
ret = sunxi_ir_hw_init(dev);
if (ret)
goto exit_unregister_dev;
...
exit_unregister_dev:
rc_unregister_device(ir->rc);
exit_free_dev:
rc_free_device(ir->rc);
}
[Severity: High]
This is a pre-existing issue, but is it safe to request the IRQ before the
hardware clocks are initialized?
If a pending interrupt from the bootloader or a spurious IRQ triggers
sunxi_ir_irq() before sunxi_ir_hw_init() enables the clock, could this lead
to a synchronous external abort when the handler reads ir->base?
[Severity: High]
This is another pre-existing issue, but does the error path for a failed
sunxi_ir_hw_init() leave the devm-managed IRQ active until the probe function
returns?
If an interrupt fires during this window, could the handler dereference
ir->rc after it has been freed by rc_free_device() at the exit_free_dev
label?
--
Sashiko AI review · https://sashiko.dev/#/patchset/cover.1785158244.git.sean@mess.org?part=6
^ permalink raw reply [flat|nested] 2+ messages in thread