[PATCH net-next] net: shaper: Reject zero weight in shaper config

[PATCH net-next] net: shaper: Reject zero weight in shaper config

[Mohsin Bashir]

A zero weight is meaningless for DWRR scheduling and can cause
starvation of the affected node. Add a min-value constraint to
the weight attribute in the net_shaper netlink spec so that zero
is rejected at the netlink policy level.

Found while prototyping a new driver, existing drivers are not
affected.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Mohsin Bashir <hmohsin@meta.com>
---
 Documentation/netlink/specs/net_shaper.yaml | 2 ++
 net/shaper/shaper_nl_gen.c                  | 6 +++---
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/Documentation/netlink/specs/net_shaper.yaml b/Documentation/netlink/specs/net_shaper.yaml
index 3f2ad772b64b..7216568fcfc5 100644
--- a/Documentation/netlink/specs/net_shaper.yaml
+++ b/Documentation/netlink/specs/net_shaper.yaml
@@ -106,6 +106,8 @@ attribute-sets:
       -
         name: weight
         type: u32
+        checks:
+          min: 1
         doc: |
           Relative weight for round robin scheduling of the
           given shaper.
diff --git a/net/shaper/shaper_nl_gen.c b/net/shaper/shaper_nl_gen.c
index 9b29be3ef19a..0cad1a355350 100644
--- a/net/shaper/shaper_nl_gen.c
+++ b/net/shaper/shaper_nl_gen.c
@@ -20,7 +20,7 @@ const struct nla_policy net_shaper_handle_nl_policy[NET_SHAPER_A_HANDLE_ID + 1]
 const struct nla_policy net_shaper_leaf_info_nl_policy[NET_SHAPER_A_WEIGHT + 1] = {
 	[NET_SHAPER_A_HANDLE] = NLA_POLICY_NESTED(net_shaper_handle_nl_policy),
 	[NET_SHAPER_A_PRIORITY] = { .type = NLA_U32, },
-	[NET_SHAPER_A_WEIGHT] = { .type = NLA_U32, },
+	[NET_SHAPER_A_WEIGHT] = NLA_POLICY_MIN(NLA_U32, 1),
 };
 
 /* NET_SHAPER_CMD_GET - do */
@@ -43,7 +43,7 @@ static const struct nla_policy net_shaper_set_nl_policy[NET_SHAPER_A_IFINDEX + 1
 	[NET_SHAPER_A_BW_MAX] = { .type = NLA_UINT, },
 	[NET_SHAPER_A_BURST] = { .type = NLA_UINT, },
 	[NET_SHAPER_A_PRIORITY] = { .type = NLA_U32, },
-	[NET_SHAPER_A_WEIGHT] = { .type = NLA_U32, },
+	[NET_SHAPER_A_WEIGHT] = NLA_POLICY_MIN(NLA_U32, 1),
 };
 
 /* NET_SHAPER_CMD_DELETE - do */
@@ -62,7 +62,7 @@ static const struct nla_policy net_shaper_group_nl_policy[NET_SHAPER_A_LEAVES +
 	[NET_SHAPER_A_BW_MAX] = { .type = NLA_UINT, },
 	[NET_SHAPER_A_BURST] = { .type = NLA_UINT, },
 	[NET_SHAPER_A_PRIORITY] = { .type = NLA_U32, },
-	[NET_SHAPER_A_WEIGHT] = { .type = NLA_U32, },
+	[NET_SHAPER_A_WEIGHT] = NLA_POLICY_MIN(NLA_U32, 1),
 	[NET_SHAPER_A_LEAVES] = NLA_POLICY_NESTED(net_shaper_leaf_info_nl_policy),
 };
 
-- 
2.52.0