On 2023-09-28 06:40, Pablo Neira Ayuso wrote:

On Wed, Sep 27, 2023 at 09:47:14AM -0700, joao@overdrivepizza.com 
wrote:

quoted

From: Joao Moreira <redacted>

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 <redacted>
---
 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?

quoted

 	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