Re: [PATCH v3 1/2] Make loop indexes unsigned

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On 2023-09-28 06:40, Pablo Neira Ayuso wrote:
On Wed, Sep 27, 2023 at 09:47:14AM -0700, joao@xxxxxxxxxxxxxxxxxx wrote:
From: Joao Moreira <joao.moreira@xxxxxxxxx>

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 -

Signed-off-by: Joao Moreira <joao.moreira@xxxxxxxxx>
 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;

With the 2^8 cap, I don't think this patch is required anymore.

Hm. While I understand that there is not a significant menace haunting this... would it be good for (1) type correctness and (2) prevent that things blow up if something changes and someone misses this spot?

 	rule = kzalloc(struct_size(rule, action.entries, num_actions),
@@ -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),

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