linux-kernel - [PATCH net 4/5] net: lan966x: Fix usage of lan966x->mac_lock inside lan966x_mac_irq

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Date:   Thu, 14 Jul 2022 21:40:39 +0200
From:   Horatiu Vultur <horatiu.vultur@...rochip.com>
To:     <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     <UNGLinuxDriver@...rochip.com>, <davem@...emloft.net>,
        <edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>,
        <vladimir.oltean@....com>,
        Horatiu Vultur <horatiu.vultur@...rochip.com>
Subject: [PATCH net 4/5] net: lan966x: Fix usage of lan966x->mac_lock inside lan966x_mac_irq_handler

The problem with this spin lock is that it was just protecting the list
of the MAC entries in SW and not also the access to the MAC entries in HW.
Because the access to HW is indirect, then it could happen to have race
conditions.
For example when SW introduced an entry in MAC table and the irq mac is
trying to read something from the MAC.
Update such that also the access to MAC entries in HW is protected by
this lock.

Fixes: 5ccd66e01cbef ("net: lan966x: add support for interrupts from analyzer")
Signed-off-by: Horatiu Vultur <horatiu.vultur@...rochip.com>
---
 .../ethernet/microchip/lan966x/lan966x_mac.c  | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_mac.c b/drivers/net/ethernet/microchip/lan966x/lan966x_mac.c
index d0b8eba0a66d..69e343b7f4af 100644
--- a/drivers/net/ethernet/microchip/lan966x/lan966x_mac.c
+++ b/drivers/net/ethernet/microchip/lan966x/lan966x_mac.c
@@ -183,7 +183,7 @@ static struct lan966x_mac_entry *lan966x_mac_alloc_entry(const unsigned char *ma
 {
 	struct lan966x_mac_entry *mac_entry;
 
-	mac_entry = kzalloc(sizeof(*mac_entry), GFP_KERNEL);
+	mac_entry = kzalloc(sizeof(*mac_entry), GFP_ATOMIC);
 	if (!mac_entry)
 		return NULL;
 
@@ -310,8 +310,8 @@ void lan966x_mac_purge_entries(struct lan966x *lan966x)
 	spin_lock(&lan966x->mac_lock);
 	list_for_each_entry_safe(mac_entry, tmp, &lan966x->mac_entries,
 				 list) {
-		lan966x_mac_forget(lan966x, mac_entry->mac, mac_entry->vid,
-				   ENTRYTYPE_LOCKED);
+		lan966x_mac_forget_locked(lan966x, mac_entry->mac,
+					  mac_entry->vid, ENTRYTYPE_LOCKED);
 
 		list_del(&mac_entry->list);
 		kfree(mac_entry);
@@ -427,13 +427,14 @@ static void lan966x_mac_irq_process(struct lan966x *lan966x, u32 row,
 		if (WARN_ON(dest_idx >= lan966x->num_phys_ports))
 			continue;
 
+		spin_lock(&lan966x->mac_lock);
 		mac_entry = lan966x_mac_alloc_entry(mac, vid, dest_idx);
-		if (!mac_entry)
+		if (!mac_entry) {
+			spin_unlock(&lan966x->mac_lock);
 			return;
+		}
 
 		mac_entry->row = row;
-
-		spin_lock(&lan966x->mac_lock);
 		list_add_tail(&mac_entry->list, &lan966x->mac_entries);
 		spin_unlock(&lan966x->mac_lock);
 
@@ -455,6 +456,7 @@ irqreturn_t lan966x_mac_irq_handler(struct lan966x *lan966x)
 	       lan966x, ANA_MACTINDX);
 
 	while (1) {
+		spin_lock(&lan966x->mac_lock);
 		lan_rmw(ANA_MACACCESS_MAC_TABLE_CMD_SET(MACACCESS_CMD_SYNC_GET_NEXT),
 			ANA_MACACCESS_MAC_TABLE_CMD,
 			lan966x, ANA_MACACCESS);
@@ -478,12 +480,15 @@ irqreturn_t lan966x_mac_irq_handler(struct lan966x *lan966x)
 			stop = false;
 
 		if (column == LAN966X_MAC_COLUMNS - 1 &&
-		    index == 0 && stop)
+		    index == 0 && stop) {
+			spin_unlock(&lan966x->mac_lock);
 			break;
+		}
 
 		entry[column].mach = lan_rd(lan966x, ANA_MACHDATA);
 		entry[column].macl = lan_rd(lan966x, ANA_MACLDATA);
 		entry[column].maca = lan_rd(lan966x, ANA_MACACCESS);
+		spin_unlock(&lan966x->mac_lock);
 
 		/* Once all the columns are read process them */
 		if (column == LAN966X_MAC_COLUMNS - 1) {
-- 
2.33.0