[PATCH 1/2] net: stmmac: Fix possible deadlock when disabling EEE support

[PATCH 1/2] net: stmmac: Fix possible deadlock when disabling EEE support

[Jon Hunter]

When stmmac_eee_init() is called to disable EEE support, then the timer
for EEE support is stopped and we return from the function. Prior to
stopping the timer, a mutex was acquired but in this case it is never
released and so could cause a deadlock. Fix this by releasing the mutex
prior to returning from stmmax_eee_init() when stopping the EEE timer.

Fixes: 74371272f97f ("net: stmmac: Convert to phylink and remove phylib logic")
Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index b628c697cee9..6c6c6ec3c781 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -402,6 +402,7 @@ bool stmmac_eee_init(struct stmmac_priv *priv)
 		netdev_dbg(priv->dev, "disable EEE\n");
 		del_timer_sync(&priv->eee_ctrl_timer);
 		stmmac_set_eee_timer(priv, priv->hw, 0, tx_lpi_timer);
+		mutex_unlock(&priv->lock);
 		return false;
 	}
 
-- 
1.9.1

[PATCH 2/2] net: stmmac: Fix crash observed if PHY does not support EEE

[Jon Hunter]

If the PHY does not support EEE mode, then a crash is observed when the
ethernet interface is enabled. The crash occurs, because if the PHY does
not support EEE, then although the EEE timer is never configured, it is
still marked as enabled and so the stmmac ethernet driver is still
trying to update the timer by calling mod_timer(). This triggers a BUG()
in the mod_timer() because we are trying to update a timer when there is
no callback function set because timer_setup() was never called for this
timer.

The problem is caused because we return true from the function
stmmac_eee_init(), marking the EEE timer as enabled, even when we have
not configured the EEE timer. Fix this by ensuring that we return false
if the PHY does not support EEE and hence, 'eee_active' is not set.

Fixes: 74371272f97f ("net: stmmac: Convert to phylink and remove phylib logic")
Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 6c6c6ec3c781..8f5ebd51859e 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -398,10 +398,12 @@ bool stmmac_eee_init(struct stmmac_priv *priv)
 	mutex_lock(&priv->lock);
 
 	/* Check if it needs to be deactivated */
-	if (!priv->eee_active && priv->eee_enabled) {
-		netdev_dbg(priv->dev, "disable EEE\n");
-		del_timer_sync(&priv->eee_ctrl_timer);
-		stmmac_set_eee_timer(priv, priv->hw, 0, tx_lpi_timer);
+	if (!priv->eee_active) {
+		if (priv->eee_enabled) {
+			netdev_dbg(priv->dev, "disable EEE\n");
+			del_timer_sync(&priv->eee_ctrl_timer);
+			stmmac_set_eee_timer(priv, priv->hw, 0, tx_lpi_timer);
+		}
 		mutex_unlock(&priv->lock);
 		return false;
 	}
-- 
1.9.1

Re: [PATCH 1/2] net: stmmac: Fix possible deadlock when disabling EEE support

[Thierry Reding]

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On Wed, Jun 26, 2019 at 11:23:21AM +0100, Jon Hunter wrote:
> When stmmac_eee_init() is called to disable EEE support, then the timer
> for EEE support is stopped and we return from the function. Prior to
> stopping the timer, a mutex was acquired but in this case it is never
> released and so could cause a deadlock. Fix this by releasing the mutex
> prior to returning from stmmax_eee_init() when stopping the EEE timer.
> 
> Fixes: 74371272f97f ("net: stmmac: Convert to phylink and remove phylib logic")
> Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 1 +
>  1 file changed, 1 insertion(+)

Tested-by: Thierry Reding <treding@nvidia.com>

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Re: [PATCH 2/2] net: stmmac: Fix crash observed if PHY does not support EEE

[Thierry Reding]

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On Wed, Jun 26, 2019 at 11:23:22AM +0100, Jon Hunter wrote:
> If the PHY does not support EEE mode, then a crash is observed when the
> ethernet interface is enabled. The crash occurs, because if the PHY does
> not support EEE, then although the EEE timer is never configured, it is
> still marked as enabled and so the stmmac ethernet driver is still
> trying to update the timer by calling mod_timer(). This triggers a BUG()
> in the mod_timer() because we are trying to update a timer when there is
> no callback function set because timer_setup() was never called for this
> timer.
> 
> The problem is caused because we return true from the function
> stmmac_eee_init(), marking the EEE timer as enabled, even when we have
> not configured the EEE timer. Fix this by ensuring that we return false
> if the PHY does not support EEE and hence, 'eee_active' is not set.
> 
> Fixes: 74371272f97f ("net: stmmac: Convert to phylink and remove phylib logic")
> Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)

Thanks for hunting this down!

Tested-by: Thierry Reding <treding@nvidia.com>

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Re: [PATCH 1/2] net: stmmac: Fix possible deadlock when disabling EEE support

[Willem de Bruijn]

On Wed, Jun 26, 2019 at 6:45 AM Thierry Reding <thierry.reding@gmail.com> wrote:
>
> On Wed, Jun 26, 2019 at 11:23:21AM +0100, Jon Hunter wrote:
> > When stmmac_eee_init() is called to disable EEE support, then the timer
> > for EEE support is stopped and we return from the function. Prior to
> > stopping the timer, a mutex was acquired but in this case it is never
> > released and so could cause a deadlock. Fix this by releasing the mutex
> > prior to returning from stmmax_eee_init() when stopping the EEE timer.
> >
> > Fixes: 74371272f97f ("net: stmmac: Convert to phylink and remove phylib logic")
> > Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
> > ---
> >  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 1 +
> >  1 file changed, 1 insertion(+)
>
> Tested-by: Thierry Reding <treding@nvidia.com>

Acked-by: Willem de Bruijn <willemb@google.com>

Re: [PATCH 1/2] net: stmmac: Fix possible deadlock when disabling EEE support

[David Miller]

From: Jon Hunter <jonathanh@nvidia.com>
Date: Wed, 26 Jun 2019 11:23:21 +0100

> When stmmac_eee_init() is called to disable EEE support, then the timer
> for EEE support is stopped and we return from the function. Prior to
> stopping the timer, a mutex was acquired but in this case it is never
> released and so could cause a deadlock. Fix this by releasing the mutex
> prior to returning from stmmax_eee_init() when stopping the EEE timer.
> 
> Fixes: 74371272f97f ("net: stmmac: Convert to phylink and remove phylib logic")
> Signed-off-by: Jon Hunter <jonathanh@nvidia.com>

When targetting net-next for a set of changes, make this explicit and clear
by saying "[PATCH net-next ...] ..." in your Subject lines in the future.

Applied.

Re: [PATCH 2/2] net: stmmac: Fix crash observed if PHY does not support EEE

[David Miller]

From: Jon Hunter <jonathanh@nvidia.com>
Date: Wed, 26 Jun 2019 11:23:22 +0100

> If the PHY does not support EEE mode, then a crash is observed when the
> ethernet interface is enabled. The crash occurs, because if the PHY does
> not support EEE, then although the EEE timer is never configured, it is
> still marked as enabled and so the stmmac ethernet driver is still
> trying to update the timer by calling mod_timer(). This triggers a BUG()
> in the mod_timer() because we are trying to update a timer when there is
> no callback function set because timer_setup() was never called for this
> timer.
> 
> The problem is caused because we return true from the function
> stmmac_eee_init(), marking the EEE timer as enabled, even when we have
> not configured the EEE timer. Fix this by ensuring that we return false
> if the PHY does not support EEE and hence, 'eee_active' is not set.
> 
> Fixes: 74371272f97f ("net: stmmac: Convert to phylink and remove phylib logic")
> Signed-off-by: Jon Hunter <jonathanh@nvidia.com>

Applied.