linux-kernel - Re: [PATCH v3] driver core: Fix device link device name collision

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Message-ID: <9ec99f2f0e1e75e11f2d7d013dc78203@walle.cc>
Date:   Fri, 08 Jan 2021 09:16:39 +0100
From:   Michael Walle <michael@...le.cc>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>, stable@...r.kernel.org,
        kernel-team@...roid.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] driver core: Fix device link device name collision

Am 2021-01-08 02:24, schrieb Saravana Kannan:
> The device link device's name was of the form:
> <supplier-dev-name>--<consumer-dev-name>
> 
> This can cause name collision as reported here [1] as device names are
> not globally unique. Since device names have to be unique within the
> bus/class, add the bus/class name as a prefix to the device names used 
> to
> construct the device link device name.
> 
> So the devuce link device's name will be of the form:
> <supplier-bus-name>:<supplier-dev-name>--<consumer-bus-name>:<consumer-dev-name>
> 
> [1] - 
> https://lore.kernel.org/lkml/20201229033440.32142-1-michael@walle.cc/
> 
> Cc: stable@...r.kernel.org
> Fixes: 287905e68dd2 ("driver core: Expose device link details in 
> sysfs")
> Reported-by: Michael Walle <michael@...le.cc>
> Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> ---
[..]

The changes are missing for the error path and 
devlink_remove_symlinks(),
right?

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 4140a69dfe18..385e16d92874 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -485,7 +485,7 @@ static int devlink_add_symlinks(struct device *dev,
  	goto out;

  err_sup_dev:
-	snprintf(buf, len, "consumer:%s", dev_name(con));
+	snprintf(buf, len, "consumer:%s:%s", dev_bus_name(con), 
dev_name(con));
  	sysfs_remove_link(&sup->kobj, buf);
  err_con_dev:
  	sysfs_remove_link(&link->link_dev.kobj, "consumer");
@@ -508,7 +508,9 @@ static void devlink_remove_symlinks(struct device 
*dev,
  	sysfs_remove_link(&link->link_dev.kobj, "consumer");
  	sysfs_remove_link(&link->link_dev.kobj, "supplier");

-	len = max(strlen(dev_name(sup)), strlen(dev_name(con)));
+	len = max(strlen(dev_bus_name(sup)) + strlen(dev_name(sup)),
+		  strlen(dev_bus_name(con)) + strlen(dev_name(con)));
+	len += strlen(":");
  	len += strlen("supplier:") + 1;
  	buf = kzalloc(len, GFP_KERNEL);
  	if (!buf) {
@@ -516,9 +518,9 @@ static void devlink_remove_symlinks(struct device 
*dev,
  		return;
  	}

-	snprintf(buf, len, "supplier:%s", dev_name(sup));
+	snprintf(buf, len, "supplier:%s:%s", dev_bus_name(sup), 
dev_name(sup));
  	sysfs_remove_link(&con->kobj, buf);
-	snprintf(buf, len, "consumer:%s", dev_name(con));
+	snprintf(buf, len, "consumer:%s:%s", dev_bus_name(sup), 
dev_name(con));
  	sysfs_remove_link(&sup->kobj, buf);
  	kfree(buf);
  }

With these changes:

Tested-by: Michael Walle <michael@...le.cc>

This at least make the warning go away.
BUT, there is somesthing strange or at least I don't get it:

# find /sys/bus/pci/devices/0000:00:00.0/ -name "consumer\:*"
# find /sys/bus/pci/devices/0000:00:00.1/ -name "consumer\:*"
/sys/bus/pci/devices/0000:00:00.1/consumer:mdio_bus:0000:00:00.1:04
/sys/bus/pci/devices/0000:00:00.1/consumer:mdio_bus:0000:00:00.1

enetc0 (0000:00:00.0) has no consumers while enetc1 (0000:00:00.1)
has ones. Although both have PHYs connected. Here are the
corresonding device tree entries:

enetc0:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/boot/dts/freescale/fsl-ls1028a-kontron-sl28.dts?h=v5.11-rc2#n81

enetc1:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/boot/dts/freescale/fsl-ls1028a-kontron-sl28-var4.dts?h=v5.11-rc2#n21

Why is there a link between enetc1 and its PHY (and MDIO bus)
but not for enetc0?

btw, here are all links:

# ls /sys/class/devlink/
pci:0000:00:00.1--mdio_bus:0000:00:00.1
platform:5000000.iommu--pci:0000:00:00.0
platform:5000000.iommu--pci:0000:00:00.1
platform:5000000.iommu--pci:0000:00:00.2
platform:5000000.iommu--pci:0000:00:00.3
platform:5000000.iommu--pci:0000:00:00.5
platform:5000000.iommu--pci:0000:00:00.6
platform:5000000.iommu--pci:0001:00:00.0
platform:5000000.iommu--pci:0002:00:00.0
platform:5000000.iommu--platform:2140000.mmc
platform:5000000.iommu--platform:2150000.mmc
platform:5000000.iommu--platform:22c0000.dma-controller
platform:5000000.iommu--platform:3100000.usb
platform:5000000.iommu--platform:3110000.usb
platform:5000000.iommu--platform:3200000.sata
platform:5000000.iommu--platform:8000000.crypto
platform:5000000.iommu--platform:8380000.dma-controller
platform:5000000.iommu--platform:f080000.display
platform:f1f0000.clock-controller--platform:f080000.display
regulator:regulator.0--i2c:0-0050
regulator:regulator.0--i2c:1-0057
regulator:regulator.0--i2c:2-0050
regulator:regulator.0--platform:3200000.sata

-- 
-michael