Re: [PATCH net 2/2] fsl/fman: Fix refcount handling of fman-related devices

From: Paolo Abeni
Date: Thu Oct 17 2024 - 06:01:39 EST


On 10/15/24 08:01, Aleksandr Mishin wrote:
In mac_probe() there are multiple calls to of_find_device_by_node(),
fman_bind() and fman_port_bind() which takes references to of_dev->dev.
Not all references taken by these calls are released later on error path
in mac_probe() and in mac_remove() which lead to reference leaks.

Add references release.

Fixes: 3933961682a3 ("fsl/fman: Add FMan MAC driver")
Signed-off-by: Aleksandr Mishin <amishin@xxxxxxxxxx>
---
Compile tested only.

drivers/net/ethernet/freescale/fman/mac.c | 62 +++++++++++++++++------
1 file changed, 47 insertions(+), 15 deletions(-)

diff --git a/drivers/net/ethernet/freescale/fman/mac.c b/drivers/net/ethernet/freescale/fman/mac.c
index 9b863db0bf08..11da139082e1 100644
--- a/drivers/net/ethernet/freescale/fman/mac.c
+++ b/drivers/net/ethernet/freescale/fman/mac.c
@@ -204,7 +204,7 @@ static int mac_probe(struct platform_device *_of_dev)
if (err) {
dev_err(dev, "failed to read cell-index for %pOF\n", dev_node);
err = -EINVAL;
- goto _return_of_node_put;
+ goto _return_dev_put;

We are after a succesful of_find_device_by_node and prior to fman_bind(), mac_dev->fman_dev refcount is 1

@@ -213,40 +213,51 @@ static int mac_probe(struct platform_device *_of_dev)
if (!priv->fman) {
dev_err(dev, "fman_bind(%pOF) failed\n", dev_node);
err = -ENODEV;
- goto _return_of_node_put;
+ goto _return_dev_put;
}
+ /* Two references have been taken in of_find_device_by_node()
+ * and fman_bind(). Release one of them here. The second one
+ * will be released in mac_remove().
+ */
+ put_device(mac_dev->fman_dev);
of_node_put(dev_node);
+ dev_node = NULL;
/* Get the address of the memory mapped registers */
mac_dev->res = platform_get_mem_or_io(_of_dev, 0);
if (!mac_dev->res) {
dev_err(dev, "could not get registers\n");
- return -EINVAL;
+ err = -EINVAL;
+ goto _return_dev_put;

Here we are after a successful fman_bind(), mac_dev->fman_dev refcount is 2. _return_dev_put will drop a single reference, this error path looks buggy.

Similar issue for the _return_dev_arr_put error path below.

Cheers,

Paolo