Re: [PATCH net-next v2 2/2] net: wwan: qcom_bam_dmux: Assign restricted DMA pool to remote processor

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] wwan: qcom_bam_dmux: probe error path reclaims DMA pool before disabling IRQ
--

commit 4ad4e0793e663284df130f5d11d5a4f0bb1754cc
Author: Vishnu Santhosh <vishnu.santhosh@oss.qualcomm.com>

net: wwan: qcom_bam_dmux: Assign restricted DMA pool to remote processor

This commit introduces restricted DMA pool support to the BAM-DMUX WWAN
network driver for Qualcomm SoCs. It assigns the pool to local and remote
execution environments during probe and reclaims it on driver removal
or probe failure.

> diff --git a/drivers/net/wwan/qcom_bam_dmux.c b/drivers/net/wwan/qcom_bam_dmux.c
> index cc6ace8d64371..c81e668d4e961 100644
> --- a/drivers/net/wwan/qcom_bam_dmux.c
> +++ b/drivers/net/wwan/qcom_bam_dmux.c

[ ... ]

> @@ -845,6 +938,7 @@ static int bam_dmux_probe(struct platform_device *pdev)
>  err_disable_pm:
>  	pm_runtime_disable(dev);
>  	pm_runtime_dont_use_autosuspend(dev);
> +	bam_dmux_reclaim_dma_pool(dmux);
>  	return ret;
>  }

[Severity: High]
Could reclaiming the DMA pool here lead to an XPU violation and resource
leak if an interrupt fires concurrently?

If probe fails late (for example, if irq_get_irqchip_state() returns an
error), the code jumps to the err_disable_pm label. At this point, the
pc_irq has already been requested via devm_request_threaded_irq() and
is active. 

If the remote processor triggers this interrupt, the threaded handler
(bam_dmux_pc_irq) could be executing bam_dmux_power_on() while we are
calling bam_dmux_reclaim_dma_pool().

This concurrent execution would cause the DMA pool to be reclaimed
while the BAM DMA controller is actively using it, resulting in a system
crash. Furthermore, when devres eventually frees the IRQ, any DMA
channels or mappings allocated by the racing handler would leak because
bam_dmux_power_off() is not called in this error path.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260920-qcom-bam-dmux-vmid-ext-v2-0-ef5ca2178378@oss.qualcomm.com?part=2