linux-kernel - [PATCH v3 1/2] Make loop indexes unsigned

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Message-ID: <20230927164715.76744-2-joao@overdrivepizza.com>
Date:   Wed, 27 Sep 2023 09:47:14 -0700
From:   joao@...rdrivepizza.com
To:     pablo@...filter.org, netfilter-devel@...r.kernel.org,
        coreteam@...filter.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, joao@...rdrivepizza.com
Cc:     kadlec@...filter.org, fw@...len.de, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        rkannoth@...vell.com, wojciech.drewek@...el.com,
        steen.hegenlund@...rohip.com, keescook@...omium.org,
        Joao Moreira <joao.moreira@...el.com>
Subject: [PATCH v3 1/2] Make loop indexes unsigned

From: Joao Moreira <joao.moreira@...el.com>

Both flow_rule_alloc and offload_action_alloc functions received an
unsigned num_actions parameters which are then operated within a loop.
The index of this loop is declared as a signed int. If it was possible
to pass a large enough num_actions to these functions, it would lead to
an out of bounds write.

After checking with maintainers, it was mentioned that front-end will
cap the num_actions value and that it is not possible to reach this
function with such a large number. Yet, for correctness, it is still
better to fix this.

This issue was observed by the commit author while reviewing a write-up
regarding a CVE within the same subsystem [1].

1 - https://nickgregory.me/post/2022/03/12/cve-2022-25636/

Signed-off-by: Joao Moreira <joao.moreira@...el.com>
---
 net/core/flow_offload.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/core/flow_offload.c b/net/core/flow_offload.c
index bc5169482710..bc3f53a09d8f 100644
--- a/net/core/flow_offload.c
+++ b/net/core/flow_offload.c
@@ -10,7 +10,7 @@
 struct flow_rule *flow_rule_alloc(unsigned int num_actions)
 {
 	struct flow_rule *rule;
-	int i;
+	unsigned int i;
 
 	rule = kzalloc(struct_size(rule, action.entries, num_actions),
 		       GFP_KERNEL);
@@ -31,7 +31,7 @@ EXPORT_SYMBOL(flow_rule_alloc);
 struct flow_offload_action *offload_action_alloc(unsigned int num_actions)
 {
 	struct flow_offload_action *fl_action;
-	int i;
+	unsigned int i;
 
 	fl_action = kzalloc(struct_size(fl_action, action.entries, num_actions),
 			    GFP_KERNEL);
-- 
2.42.0