[v4,1/6] phy: core: Fix that API devm_phy_put() fails to release the phy

Commit Message

Zijun Hu Nov. 2, 2024, 3:53 a.m. UTC

From: Zijun Hu <[e-mail]>

For devm_phy_put(), its comment says it needs to invoke phy_put() to
release the phy, but it will not actually invoke the function since
devres_destroy() does not call devm_phy_release(), and the missing
phy_put() call will cause:

- The phy fails to be released.
- devm_phy_put() can not fully undo what API devm_phy_get() does.
- Leak refcount of both the module and device for below typical usage:

  devm_phy_get(); // or its variant
  ...
  err = do_something();
  if (err)
      goto err_out;
  ...
  err_out:
  devm_phy_put(); // leak refcount here

  The file(s) affected by this issue are shown below since they have such
  typical usage.
  drivers/pci/controller/cadence/pcie-cadence.c
  drivers/net/ethernet/ti/am65-cpsw-nuss.c

Fixed by using devres_release() instead of devres_destroy() within the API.

Fixes: ff764963479a ("drivers: phy: add generic PHY framework")
Cc: [e-mail]
Cc: Lorenzo Pieralisi <[e-mail]>
Cc: "Krzysztof Wilczyński" <[e-mail]>
Cc: Bjorn Helgaas <[e-mail]>
Cc: "David S. Miller" <[e-mail]>
Cc: Eric Dumazet <[e-mail]>
Cc: Jakub Kicinski <[e-mail]>
Cc: Paolo Abeni <[e-mail]>
Cc: Johan Hovold <[e-mail]>
Signed-off-by: Zijun Hu <[e-mail]>
---
 drivers/phy/phy-core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Johan Hovold Nov. 5, 2024, 5:13 p.m. UTC | #1

On Sat, Nov 02, 2024 at 11:53:43AM +0800, Zijun Hu wrote:
> From: Zijun Hu <[e-mail]>
> 
> For devm_phy_put(), its comment says it needs to invoke phy_put() to
> release the phy, but it will not actually invoke the function since
> devres_destroy() does not call devm_phy_release(), and the missing
> phy_put() call will cause:

I still think the above should have been split in two sentences, but
this also works.

> - The phy fails to be released.
> - devm_phy_put() can not fully undo what API devm_phy_get() does.
> - Leak refcount of both the module and device for below typical usage:
> 
>   devm_phy_get(); // or its variant
>   ...
>   err = do_something();
>   if (err)
>       goto err_out;
>   ...
>   err_out:
>   devm_phy_put(); // leak refcount here
> 
>   The file(s) affected by this issue are shown below since they have such
>   typical usage.
>   drivers/pci/controller/cadence/pcie-cadence.c
>   drivers/net/ethernet/ti/am65-cpsw-nuss.c
> 
> Fixed by using devres_release() instead of devres_destroy() within the API.

Nit: in the future, try to use imperative mood in your commit messages
(e.g. "fix" instead of "fixed") as the process documentation suggests.

> Fixes: ff764963479a ("drivers: phy: add generic PHY framework")
> Cc: [e-mail]
> Cc: Lorenzo Pieralisi <[e-mail]>
> Cc: "Krzysztof Wilczyński" <[e-mail]>
> Cc: Bjorn Helgaas <[e-mail]>
> Cc: "David S. Miller" <[e-mail]>
> Cc: Eric Dumazet <[e-mail]>
> Cc: Jakub Kicinski <[e-mail]>
> Cc: Paolo Abeni <[e-mail]>
> Cc: Johan Hovold <[e-mail]>
> Signed-off-by: Zijun Hu <[e-mail]>

Reviewed-by: Johan Hovold <[e-mail]>

Patch

diff --git a/drivers/phy/phy-core.c b/drivers/phy/phy-core.c
index f053b525ccff..f190d7126613 100644
--- a/drivers/phy/phy-core.c
+++ b/drivers/phy/phy-core.c
@@ -737,7 +737,7 @@  void devm_phy_put(struct device *dev, struct phy *phy)
 	if (!phy)
 		return;
 
-	r = devres_destroy(dev, devm_phy_release, devm_phy_match, phy);
+	r = devres_release(dev, devm_phy_release, devm_phy_match, phy);
 	dev_WARN_ONCE(dev, r, "couldn't find PHY resource\n");
 }
 EXPORT_SYMBOL_GPL(devm_phy_put);