[PATCH AUTOSEL 5.4 052/130] net: dsa: avoid potential use-after-free error

Sasha Levin
2020-12-23T02:59:25Z

From: Christian Eggers <ceggers@arri.de>

[ Upstream commit 30abc9cd9c6bdd44d23fc49a9c2526a86fba4305 ]

If dsa_switch_ops::port_txtstamp() returns false, clone will be freed
immediately. Shouldn't store a pointer to freed memory.

Signed-off-by: Christian Eggers <ceggers@arri.de>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Tested-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20201119110906.25558-1-ceggers@arri.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/dsa/slave.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index f734ce0bcb56e..2b657e88d8017 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -476,10 +476,10 @@ static void dsa_skb_tx_timestamp(struct dsa_slave_priv *p,
if (!clone)
return;

- DSA_SKB_CB(skb)->clone = clone;
-
- if (ds->ops->port_txtstamp(ds, p->dp->index, clone, type))
+ if (ds->ops->port_txtstamp(ds, p->dp->index, clone, type)) {
+ DSA_SKB_CB(skb)->clone = clone;
return;
+ }

kfree_skb(clone);
}
--
2.27.0