Re: [PATCH] dmaengine: qcom: hidma: avoid world-writable channel sysfs files

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found no new issues
in this patch, but noticed 1 related pre-existing issue it does not
introduce:
- [Critical] dmaengine: qcom: hidma_mgmt: kobject leak and UAF in
  hidma_mgmt_init_sys() [1]
--

commit 44ad6eea44504d623e4ff527b7da4680661c450d
Author: Hungyu Lin <dennylin0707@gmail.com>

dmaengine: qcom: hidma: avoid world-writable channel sysfs files

This commit restricts the per-channel priority and weight sysfs attributes
in hidma_mgmt_init_sys() from world-writable (S_IRUGO | S_IWUGO) to 0644.

> diff --git a/drivers/dma/qcom/hidma_mgmt_sys.c b/drivers/dma/qcom/hidma_mgmt_sys.c
> index 9672ef9ee8fc0..53b991752e805 100644
> --- a/drivers/dma/qcom/hidma_mgmt_sys.c
> +++ b/drivers/dma/qcom/hidma_mgmt_sys.c
> @@ -265,13 +265,13 @@ int hidma_mgmt_init_sys(struct hidma_mgmt_dev *mdev)
>  	/* populate parameters that are per channel */
>  	for (i = 0; i < mdev->dma_channels; i++) {
>  		rc = create_sysfs_entry_channel(mdev, "priority",
> -						(S_IRUGO | S_IWUGO), i,
> +						0644, i,
>  						mdev->chroots[i]);
>  		if (rc)
>  			return rc;
>  
>  		rc = create_sysfs_entry_channel(mdev, "weight",
> -						(S_IRUGO | S_IWUGO), i,
> +						0644, i,
>  						mdev->chroots[i]);
>  		if (rc)
>  			return rc;

[Severity: Critical]
This problem wasn't introduced by this patch, but does hidma_mgmt_init_sys()
leak kobjects and leave dangling sysfs attributes on failure or driver
unbind [1]?

If any step in hidma_mgmt_init_sys() fails, it returns without calling
kobject_put() on chanops or mdev->chroots[i] or removing previously created
sysfs files, and hidma_mgmt_driver has no .remove callback to clean them up
on unbind either.  Because the attribute structs, names, and mdev itself are
allocated with devm_kmalloc(), devres frees them on probe failure or device
unbind while the sysfs files remain exposed, causing a use-after-free when
userspace reads or writes those attributes.

[1] https://sashiko.dev/#/bug/linux-68f0e3d9-2e4a-4922-9d34-c92a40fad2aa

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261107221500.96825-1-dennylin0707@gmail.com?part=1