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

From: Thierry Reding <[email-masked]>
Date: Wed, 26 Jun 2019 12:45:44 +0200

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 <[email-masked]>
> ---
>  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 <[email-masked]>