[PATCH 5.17 0709/1126] drivers: ethernet: cpsw: fix panic when interrupt coaleceing is set via ethtool

From: Greg Kroah-Hartman
Date: Tue Apr 05 2022 - 05:51:55 EST

From: Sondhauß, Jan <Jan.Sondhauss@xxxxxxxx>

[ Upstream commit 2844e2434385819f674d1fb4130c308c50ba681e ]

cpsw_ethtool_begin directly returns the result of pm_runtime_get_sync
when successful.
pm_runtime_get_sync returns -error code on failure and 0 on successful
resume but also 1 when the device is already active. So the common case
for cpsw_ethtool_begin is to return 1. That leads to inconsistent calls
to pm_runtime_put in the call-chain so that pm_runtime_put is called
one too many times and as result leaving the cpsw dev behind suspended.

The suspended cpsw dev leads to an access violation later on by
different parts of the cpsw driver.

Fix this by calling the return-friendly pm_runtime_resume_and_get

Fixes: d43c65b05b84 ("ethtool: runtime-resume netdev parent in ethnl_ops_begin")
Signed-off-by: Jan Sondhauss <jan.sondhauss@xxxxxxxx>
Reviewed-by: Vignesh Raghavendra <vigneshr@xxxxxx>
Link: https://lore.kernel.org/r/20220323084725.65864-1-jan.sondhauss@xxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
drivers/net/ethernet/ti/cpsw_ethtool.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/ti/cpsw_ethtool.c b/drivers/net/ethernet/ti/cpsw_ethtool.c
index aa42141be3c0..a557a477d039 100644
--- a/drivers/net/ethernet/ti/cpsw_ethtool.c
+++ b/drivers/net/ethernet/ti/cpsw_ethtool.c
@@ -364,11 +364,9 @@ int cpsw_ethtool_op_begin(struct net_device *ndev)
struct cpsw_common *cpsw = priv->cpsw;
int ret;

- ret = pm_runtime_get_sync(cpsw->dev);
- if (ret < 0) {
+ ret = pm_runtime_resume_and_get(cpsw->dev);
+ if (ret < 0)
cpsw_err(priv, drv, "ethtool begin failed %d\n", ret);
- pm_runtime_put_noidle(cpsw->dev);
- }

return ret;