[PATCH AUTOSEL 4.14 038/105] net: sfp: add mutex to prevent concurrent state checks

Sasha Levin
2019-07-15T14:30:59Z

From: Robert Hancock <hancock@sedsystems.ca>

[ Upstream commit 2158e856f56bb762ef90f3ec244d41a519826f75 ]

sfp_check_state can potentially be called by both a threaded IRQ handler
and delayed work. If it is concurrently called, it could result in
incorrect state management. Add a st_mutex to protect the state - this
lock gets taken outside of code that checks and handle state changes, and
the existing sm_mutex nests inside of it.

Suggested-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Robert Hancock <hancock@sedsystems.ca>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/phy/sfp.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/net/phy/sfp.c b/drivers/net/phy/sfp.c
index 2dcb25aa0452..9cef89fe410d 100644
--- a/drivers/net/phy/sfp.c
+++ b/drivers/net/phy/sfp.c
@@ -115,10 +115,11 @@ struct sfp {
struct gpio_desc *gpio[GPIO_MAX];

bool attached;
+ struct mutex st_mutex; /* Protects state */
unsigned int state;
struct delayed_work poll;
struct delayed_work timeout;
- struct mutex sm_mutex;
+ struct mutex sm_mutex; /* Protects state machine */
unsigned char sm_mod_state;
unsigned char sm_dev_state;
unsigned short sm_state;
@@ -738,6 +739,7 @@ static void sfp_check_state(struct sfp *sfp)
{
unsigned int state, i, changed;

+ mutex_lock(&sfp->st_mutex);
state = sfp_get_state(sfp);
changed = state ^ sfp->state;
changed &= SFP_F_PRESENT | SFP_F_LOS | SFP_F_TX_FAULT;
@@ -763,6 +765,7 @@ static void sfp_check_state(struct sfp *sfp)
sfp_sm_event(sfp, state & SFP_F_LOS ?
SFP_E_LOS_HIGH : SFP_E_LOS_LOW);
rtnl_unlock();
+ mutex_unlock(&sfp->st_mutex);
}

static irqreturn_t sfp_irq(int irq, void *data)
@@ -793,6 +796,7 @@ static struct sfp *sfp_alloc(struct device *dev)
sfp->dev = dev;

mutex_init(&sfp->sm_mutex);
+ mutex_init(&sfp->st_mutex);
INIT_DELAYED_WORK(&sfp->poll, sfp_poll);
INIT_DELAYED_WORK(&sfp->timeout, sfp_timeout);

--
2.20.1