[Openvpn-devel] [PATCH ovpn net v6 1/6] ovpn: fix NULL dereference when killing missing key

ovpn_crypto_kill_key assumes both crypto slots are populated and
dereferences each slot before checking it. That is not guaranteed: a
peer can have only one installed key, and the kill path may be asked to
remove a key that is not present.

Read each slot once while holding the crypto state lock, check for NULL
before looking at key_id, and only replace the slot that actually
matches.

Fixes: 89d3c0e4612a ("ovpn: kill key and notify userspace in case of IV exhaustion")
Signed-off-by: Ralf Lici <[email protected]>
---
Changes since v5 https://lore.kernel.org/openvpn-devel/b2f5120a3efa20c62a83397d96e949eac6a983df.1783336121.git.ralf@mandelbit.com/
- Rework using the slot-based shape (Sabrina).

Changes since v4 of this series https://lore.kernel.org/openvpn-devel/981d2ea51cca45138210aa52c6e5a0e55c0da7a0.1783099626.git.ralf@mandelbit.com/
- Add this previously posted standalone fix to the series so the whole
  set can be picked in order.
- No changes since v2 of the original single patch
  https://lore.kernel.org/openvpn-devel/19318904cf077d067cd4ec628a22bab03ed7dd29.1782993857.git.ralf@mandelbit.com/

Changes since v1 of the original single patch https://lore.kernel.org/openvpn-devel/9fc33e6f9fae10b9e372a3e06934d697edf5b024.1782829171.git.ralf@mandelbit.com/
- Remove unnecessary braces around single-statement if/else branches.

 drivers/net/ovpn/crypto.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ovpn/crypto.c b/drivers/net/ovpn/crypto.c
index 90580e32052f..2e95f29514fc 100644
--- a/drivers/net/ovpn/crypto.c
+++ b/drivers/net/ovpn/crypto.c
@@ -58,15 +58,19 @@ void ovpn_crypto_state_release(struct ovpn_crypto_state *cs)
 bool ovpn_crypto_kill_key(struct ovpn_crypto_state *cs, u8 key_id)
 {
 	struct ovpn_crypto_key_slot *ks = NULL;
+	struct ovpn_crypto_key_slot *tmp;
+	int slot = 0;
 
 	spin_lock_bh(&cs->lock);
-	if (rcu_access_pointer(cs->slots[0])->key_id == key_id) {
-		ks = rcu_replace_pointer(cs->slots[0], NULL,
-					 lockdep_is_held(&cs->lock));
-	} else if (rcu_access_pointer(cs->slots[1])->key_id == key_id) {
-		ks = rcu_replace_pointer(cs->slots[1], NULL,
-					 lockdep_is_held(&cs->lock));
+	tmp = rcu_access_pointer(cs->slots[slot]);
+	if (!tmp || tmp->key_id != key_id) {
+		slot = 1;
+		tmp = rcu_access_pointer(cs->slots[slot]);
 	}
+
+	if (tmp && tmp->key_id == key_id)
+		ks = rcu_replace_pointer(cs->slots[slot], NULL,
+					 lockdep_is_held(&cs->lock));
 	spin_unlock_bh(&cs->lock);
 
 	if (ks)
-- 
2.55.0



_______________________________________________
Openvpn-devel mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/openvpn-devel