This is a note to let you know that I've just added the patch titled net: mscc: ocelot: fix mutex lock error during ethtool stats read to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: net-mscc-ocelot-fix-mutex-lock-error-during-ethtool-.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 17d1b7d55877864f104a7c064416b44e40e64d95 Author: Colin Foster <colin.foster@xxxxxxxxxxxxxxxx> Date: Thu Feb 10 07:04:51 2022 -0800 net: mscc: ocelot: fix mutex lock error during ethtool stats read [ 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@xxxxxxxxxxxxxxxx> Fixes: 1e1caa9735f90 ("ocelot: Clean up stats update deferred work") Fixes: a556c76adc052 ("net: mscc: Add initial Ocelot switch support") Reported-by: Vladimir Oltean <vladimir.oltean@xxxxxxx> Reviewed-by: Vladimir Oltean <vladimir.oltean@xxxxxxx> Link: https://lore.kernel.org/all/20220210150451.416845-2-colin.foster@xxxxxxxxxxxxxxxx/ Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/drivers/net/ethernet/mscc/ocelot.c b/drivers/net/ethernet/mscc/ocelot.c index be2dd69bfee8b..6aad0953e8fe5 100644 --- a/drivers/net/ethernet/mscc/ocelot.c +++ b/drivers/net/ethernet/mscc/ocelot.c @@ -1215,12 +1215,11 @@ 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); @@ -1239,8 +1238,6 @@ 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) @@ -1249,7 +1246,9 @@ 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); @@ -1259,12 +1258,16 @@ 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);