[PATCH 6.1 0470/1146] hsr: Add a rcu-read lock to hsr_forward_skb().

Greg Kroah-Hartman
2022-12-28T16:01:16Z

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

[ Upstream commit 5aa2820177af650293b2f9f1873c1f6f8e4ad7a4 ]

hsr_forward_skb() a skb and keeps information in an on-stack
hsr_frame_info. hsr_get_node() assigns hsr_frame_info::node_src which is
from a RCU list. This pointer is used later in hsr_forward_do().
I don't see a reason why this pointer can't vanish midway since there is
no guarantee that hsr_forward_skb() is invoked from an RCU read section.

Use rcu_read_lock() to protect hsr_frame_info::node_src from its
assignment until it is no longer used.

Fixes: f266a683a4804 ("net/hsr: Better frame dispatch")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/hsr/hsr_forward.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/net/hsr/hsr_forward.c b/net/hsr/hsr_forward.c
index 3e58d310b4d4..a8befa35841e 100644
--- a/net/hsr/hsr_forward.c
+++ b/net/hsr/hsr_forward.c
@@ -614,11 +614,13 @@ void hsr_forward_skb(struct sk_buff *skb, struct hsr_port *port)
{
struct hsr_frame_info frame;

+ rcu_read_lock();
if (fill_frame_info(&frame, skb, port) < 0)
goto out_drop;

hsr_register_frame_in(frame.node_src, port, frame.sequence_nr);
hsr_forward_do(&frame);
+ rcu_read_unlock();
/* Gets called for ingress frames as well as egress from master port.
* So check and increment stats for master port only here.
*/
@@ -633,6 +635,7 @@ void hsr_forward_skb(struct sk_buff *skb, struct hsr_port *port)
return;

out_drop:
+ rcu_read_unlock();
port->dev->stats.tx_dropped++;
kfree_skb(skb);
}
--
2.35.1