[PATCH 5.10 085/116] net: mscc: ocelot: fix mutex lock error during ethtool stats read

Greg Kroah-Hartman
2022-02-14T09:56:53Z

From: Colin Foster <colin.foster@in-advantage.com>

[ Upstream commit 7fbf6795d127a3b1bb39b0e42579904cf6db1624 ]

An ongoing workqueue populates the stats buffer. At the same time, a user
might query the statistics. While writing to the buffer is mutex-locked,
reading from the buffer wasn't. This could lead to buggy reads by ethtool.

This patch fixes the former blamed commit, but the bug was introduced in
the latter.

Signed-off-by: Colin Foster <colin.foster@in-advantage.com>
Fixes: 1e1caa9735f90 ("ocelot: Clean up stats update deferred work")
Fixes: a556c76adc052 ("net: mscc: Add initial Ocelot switch support")
Reported-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://lore.kernel.org/all/20220210150451.416845-2-colin.foster@in-advantage.com/
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/ethernet/mscc/ocelot.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/mscc/ocelot.c b/drivers/net/ethernet/mscc/ocelot.c
index 52401915828a1..a06466ecca12a 100644
--- a/drivers/net/ethernet/mscc/ocelot.c
+++ b/drivers/net/ethernet/mscc/ocelot.c
@@ -848,12 +848,11 @@ void ocelot_get_strings(struct ocelot *ocelot, int port, u32 sset, u8 *data)
}
EXPORT_SYMBOL(ocelot_get_strings);

+/* Caller must hold &ocelot->stats_lock */
static void ocelot_update_stats(struct ocelot *ocelot)
{
int i, j;

- mutex_lock(&ocelot->stats_lock);
-
for (i = 0; i < ocelot->num_phys_ports; i++) {
/* Configure the port to read the stats from */
ocelot_write(ocelot, SYS_STAT_CFG_STAT_VIEW(i), SYS_STAT_CFG);
@@ -872,8 +871,6 @@ static void ocelot_update_stats(struct ocelot *ocelot)
~(u64)U32_MAX) + val;
}
}
-
- mutex_unlock(&ocelot->stats_lock);
}

static void ocelot_check_stats_work(struct work_struct *work)
@@ -882,7 +879,9 @@ static void ocelot_check_stats_work(struct work_struct *work)
struct ocelot *ocelot = container_of(del_work, struct ocelot,
stats_work);

+ mutex_lock(&ocelot->stats_lock);
ocelot_update_stats(ocelot);
+ mutex_unlock(&ocelot->stats_lock);

queue_delayed_work(ocelot->stats_queue, &ocelot->stats_work,
OCELOT_STATS_CHECK_DELAY);
@@ -892,12 +891,16 @@ void ocelot_get_ethtool_stats(struct ocelot *ocelot, int port, u64 *data)
{
int i;

+ mutex_lock(&ocelot->stats_lock);
+
/* check and update now */
ocelot_update_stats(ocelot);

/* Copy all counters */
for (i = 0; i < ocelot->num_stats; i++)
*data++ = ocelot->stats[port * ocelot->num_stats + i];
+
+ mutex_unlock(&ocelot->stats_lock);
}
EXPORT_SYMBOL(ocelot_get_ethtool_stats);

--
2.34.1