[PATCH net] openvswitch: fix send of uninitialized stack memory in ct limit reply

'struct ovs_zone_limit' has more members than initialized in
ovs_ct_limit_get_default_limit().  The rest of the memory is a random
kernel stack content that ends up being sent to userspace.

Fix that by using designated initializer that will clear all
non-specified fields.

Fixes: 11efd5cb04a1 ("openvswitch: Support conntrack zone limit")
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
---
 net/openvswitch/conntrack.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
index c29b0ef1fc27..cadb6a29b285 100644
--- a/net/openvswitch/conntrack.c
+++ b/net/openvswitch/conntrack.c

@@ -2032,10 +2032,10 @@ static int ovs_ct_limit_del_zone_limit(struct nlattr *nla_zone_limit,
 static int ovs_ct_limit_get_default_limit(struct ovs_ct_limit_info *info,
 					  struct sk_buff *reply)
 {
-	struct ovs_zone_limit zone_limit;
-
-	zone_limit.zone_id = OVS_ZONE_LIMIT_DEFAULT_ZONE;
-	zone_limit.limit = info->default_limit;
+	struct ovs_zone_limit zone_limit = {
+		.zone_id = OVS_ZONE_LIMIT_DEFAULT_ZONE,
+		.limit   = info->default_limit,
+	};
 
 	return nla_put_nohdr(reply, sizeof(zone_limit), &zone_limit);
 }

-- 
2.26.2

CC: ovs-dev

On 4/4/21 7:50 PM, Ilya Maximets wrote:

On Mon, Apr 5, 2021 at 2:01 AM Ilya Maximets [off-list ref] wrote:

CC: ovs-dev

On 4/4/21 7:50 PM, Ilya Maximets wrote:

quoted

'struct ovs_zone_limit' has more members than initialized in
ovs_ct_limit_get_default_limit().  The rest of the memory is a random
kernel stack content that ends up being sent to userspace.

Fix that by using designated initializer that will clear all
non-specified fields.

Fixes: 11efd5cb04a1 ("openvswitch: Support conntrack zone limit")
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
---
 net/openvswitch/conntrack.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
index c29b0ef1fc27..cadb6a29b285 100644
--- a/net/openvswitch/conntrack.c
+++ b/net/openvswitch/conntrack.c

@@ -2032,10 +2032,10 @@ static int ovs_ct_limit_del_zone_limit(struct nlattr *nla_zone_limit,
 static int ovs_ct_limit_get_default_limit(struct ovs_ct_limit_info *info,
                                        struct sk_buff *reply)
 {
-     struct ovs_zone_limit zone_limit;
-
-     zone_limit.zone_id = OVS_ZONE_LIMIT_DEFAULT_ZONE;
-     zone_limit.limit = info->default_limit;
+     struct ovs_zone_limit zone_limit = {
+             .zone_id = OVS_ZONE_LIMIT_DEFAULT_ZONE,
+             .limit   = info->default_limit,
+     };

I review the code, userspace don't use the count of ovs_zone_lime
struct, but this patch looks to to me.
Thanks Ilya.
Acked-by: Tonghao Zhang <redacted>

quoted

      return nla_put_nohdr(reply, sizeof(zone_limit), &zone_limit);
 }

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-- 
Best regards, Tonghao

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Sun,  4 Apr 2021 19:50:31 +0200 you wrote:

'struct ovs_zone_limit' has more members than initialized in
ovs_ct_limit_get_default_limit().  The rest of the memory is a random
kernel stack content that ends up being sent to userspace.

Fix that by using designated initializer that will clear all
non-specified fields.

[...]

Here is the summary with links:
  - [net] openvswitch: fix send of uninitialized stack memory in ct limit reply
    https://git.kernel.org/netdev/net/c/4d51419d4993

You are awesome, thank you!
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