Subject: [PATCH net 01/10] ethtool: coalesce: cap profile updates at NET_DIM_PARAMS_NUM_PROFILES

From: Jakub Kicinski <[email-masked]>
Date: Tue, 26 May 2026 08:35:24 -0700

ethnl_update_profile() walks the ETHTOOL_A_PROFILE_IRQ_MODERATION
nest list with an index 'i' and writes new_profile[i++] without
bounding i. The destination is kmemdup()'d at NET_DIM_PARAMS_NUM_PROFILES
entries (5), but the Netlink nest count is entirely user-controlled.
Netlink policies do not have support for constraining the number
of nested entries (or number of multi-attr entries).

Fixes: f750dfe825b9 ("ethtool: provide customized dim profile management")
Signed-off-by: Jakub Kicinski <[email-masked]>
---
CC: [email-masked]
CC: [email-masked]
CC: [email-masked]
CC: [email-masked]
---
 net/ethtool/coalesce.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/ethtool/coalesce.c b/net/ethtool/coalesce.c
index 1e2c5c7048a8..e73fc3e5a02b 100644
--- a/net/ethtool/coalesce.c
+++ b/net/ethtool/coalesce.c
@@ -472,6 +472,12 @@ static int ethnl_update_profile(struct net_device *dev,
 
 	nla_for_each_nested_type(nest, ETHTOOL_A_PROFILE_IRQ_MODERATION,
 				 nests, rem) {
+		if (i >= NET_DIM_PARAMS_NUM_PROFILES) {
+			NL_SET_BAD_ATTR(extack, nest);
+			ret = -E2BIG;
+			goto err_out;
+		}
+
 		ret = nla_parse_nested(tb, len_irq_moder - 1, nest,
 				       coalesce_irq_moderation_policy,
 				       extack);
-- 
2.54.0