[PATCH net-next] net: dsa: Fix use after free in dsa_switch_remove()

* [PATCH net-next] net: dsa: Fix use after free in dsa_switch_remove()
@ 2019-11-03  3:13 Florian Fainelli
  2019-11-03  3:53 ` Vivien Didelot
  2019-11-06  1:55 ` David Miller
  0 siblings, 2 replies; 3+ messages in thread
From: Florian Fainelli @ 2019-11-03  3:13 UTC (permalink / raw)
  To: netdev
  Cc: rmk+kernel, hkallweit1, Florian Fainelli, Andrew Lunn,
	Vivien Didelot, David S. Miller, open list

The order in which the ports are deleted from the list and freed and the
call to dsa_tree_remove_switch() is done is reversed, which leads to an
use after free condition. Reverse the two: first tear down the ports and
switch from the fabric, then free the ports associated with that switch
fabric.

Fixes: 05f294a85235 ("net: dsa: allocate ports on touch")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
---
 net/dsa/dsa2.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/dsa/dsa2.c b/net/dsa/dsa2.c
index ff2fa3950c62..9ef2caa13f27 100644
--- a/net/dsa/dsa2.c
+++ b/net/dsa/dsa2.c
@@ -874,12 +874,13 @@ static void dsa_switch_remove(struct dsa_switch *ds)
 	struct dsa_switch_tree *dst = ds->dst;
 	struct dsa_port *dp, *next;
 
+	dsa_tree_teardown(dst);
+
 	list_for_each_entry_safe(dp, next, &dst->ports, list) {
 		list_del(&dp->list);
 		kfree(dp);
 	}
 
-	dsa_tree_teardown(dst);
 	dsa_tree_put(dst);
 }
 
-- 
2.17.1


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