linux-kernel - [PATCH v3 1/2] igb: Do not free q_vector unless new one was allocated

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Message-Id: <20221018092526.4035344-1-keescook@chromium.org>
Date:   Tue, 18 Oct 2022 02:25:24 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Ruhl@....outflux.net, Michael J <michael.j.ruhl@...el.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Tony Nguyen <anthony.l.nguyen@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH v3 1/2] igb: Do not free q_vector unless new one was allocated

Avoid potential use-after-free condition under memory pressure. If the
kzalloc() fails, q_vector will be freed but left in the original
adapter->q_vector[v_idx] array position.

Cc: Jesse Brandeburg <jesse.brandeburg@...el.com>
Cc: Tony Nguyen <anthony.l.nguyen@...el.com>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Jakub Kicinski <kuba@...nel.org>
Cc: Paolo Abeni <pabeni@...hat.com>
Cc: intel-wired-lan@...ts.osuosl.org
Cc: netdev@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/net/ethernet/intel/igb/igb_main.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index f8e32833226c..6256855d0f62 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -1202,8 +1202,12 @@ static int igb_alloc_q_vector(struct igb_adapter *adapter,
 	if (!q_vector) {
 		q_vector = kzalloc(size, GFP_KERNEL);
 	} else if (size > ksize(q_vector)) {
-		kfree_rcu(q_vector, rcu);
-		q_vector = kzalloc(size, GFP_KERNEL);
+		struct igb_q_vector *new_q_vector;
+
+		new_q_vector = kzalloc(size, GFP_KERNEL);
+		if (new_q_vector)
+			kfree_rcu(q_vector, rcu);
+		q_vector = new_q_vector;
 	} else {
 		memset(q_vector, 0, size);
 	}
-- 
2.34.1