[PATCH] dmaengine: pl08x: Create debugfs stats file under device folder

[PATCH] dmaengine: pl08x: Create debugfs stats file under device folder

[Vladimir Zapolskiy]

If parent folder for a debug file is not set, then this file is created
right in top debugfs mountpoint directory, which is undesired. However
for every DMA controller device its dedicated folder below 'dmaengine'
is created by dma_async_device_register(), and this particular folder
is expected to store all device specific debug files.

The new name "stats" is selected as the most popular debugfs file name
found in other DMA controller device drivers, and the macro constant
for file mode is replaced by the octal value.

Signed-off-by: Vladimir Zapolskiy <vz@kernel.org>
---
 drivers/dma/amba-pl08x.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/amba-pl08x.c b/drivers/dma/amba-pl08x.c
index 5e88fd44812d..543c2eb8cfa8 100644
--- a/drivers/dma/amba-pl08x.c
+++ b/drivers/dma/amba-pl08x.c
@@ -2500,8 +2500,8 @@ DEFINE_SHOW_ATTRIBUTE(pl08x_debugfs);
 static void init_pl08x_debugfs(struct pl08x_driver_data *pl08x)
 {
 	/* Expose a simple debugfs interface to view all clocks */
-	debugfs_create_file(dev_name(&pl08x->adev->dev), S_IFREG | S_IRUGO,
-			    NULL, pl08x, &pl08x_debugfs_fops);
+	debugfs_create_file("stats", 0444, pl08x->memcpy.dbg_dev_root,
+			    pl08x, &pl08x_debugfs_fops);
 }
 
 #else
-- 
2.51.0

Re: [PATCH] dmaengine: pl08x: Create debugfs stats file under device folder

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] The `amba-pl08x` driver does not implement a `.remove` callback, breaking teardown symmetry on unbind and causing severe resource leaks and Use-After-Free vulnerabilities.
--

--- Patch [1]: [PATCH] dmaengine: pl08x: Create debugfs stats file under device folder ---
commit 178237cec2bb84665705001630a35ef76e87cfb1
Author: Vladimir Zapolskiy <vz@kernel.org>

dmaengine: pl08x: Create debugfs stats file under device folder

This commit changes the debugfs initialization for the pl08x driver. It
creates a stats file under the dedicated dmaengine device folder instead of
the top-level debugfs mountpoint.

> diff --git a/drivers/dma/amba-pl08x.c b/drivers/dma/amba-pl08x.c
> index 5e88fd44812de..543c2eb8cfa81 100644
> --- a/drivers/dma/amba-pl08x.c
> +++ b/drivers/dma/amba-pl08x.c
[ ... ]
> @@ -2500,8 +2500,8 @@ DEFINE_SHOW_ATTRIBUTE(pl08x_debugfs);
>  static void init_pl08x_debugfs(struct pl08x_driver_data *pl08x)
>  {
>  	/* Expose a simple debugfs interface to view all clocks */
> -	debugfs_create_file(dev_name(&pl08x->adev->dev), S_IFREG | S_IRUGO,
> -			    NULL, pl08x, &pl08x_debugfs_fops);
> +	debugfs_create_file("stats", 0444, pl08x->memcpy.dbg_dev_root,
> +			    pl08x, &pl08x_debugfs_fops);
>  }

While reviewing this patch, I noticed an issue in the amba_driver struct
further down in the file:

drivers/dma/amba-pl08x.c:pl08x_amba_driver
static struct amba_driver pl08x_amba_driver = {
	.drv.name	= DRIVER_NAME,
	.id_table	= pl08x_ids,
	.probe		= pl08x_probe,
};

[Severity: High]
This is a pre-existing issue, but does pl08x_amba_driver need a .remove
callback to handle unbinding safely?

If an administrator unbinds the driver via sysfs or unloads the module, the
AMBA bus detaches the device without invoking any driver-specific cleanup.

Because there is no .remove callback, wouldn't this leave non-devres
resources and global subsystem registrations like dma_async_device_register
active while the module is unloaded?

Could this lead to a use-after-free or kernel panic if the dmaengine core
accesses the leaked device from the global list, or if the hardware asserts
an interrupt after the module is unloaded?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260723211739.289699-1-vz@kernel.org?part=1