Re: [PATCH net v3 1/2] net: ethtool: reject an out of range hwtstamp provider index

A provider index of 0xFFFFFFFF picks a provider on hardware that has
none. phc_index is an int where -1 means no PHC, and the u32 from user
space ends up as -1, so the two match.

TSINFO_GET uses -1 for "no provider requested" and answers with the
default provider instead of an error.

Reject the value in the netlink policy, which covers every comparison
site.

Fixes: b9e3f7dc9ed9 ("net: ethtool: tsinfo: Enhance tsinfo to support several hwtstamp by net topology")
Signed-off-by: Nicolai Buchwitz <nb@tipi-net.de>
---
NLA_POLICY_MAX does not fit here, .max in struct nla_policy is s16.

  net/ethtool/ts.h | 8 +++++++-
  1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/net/ethtool/ts.h b/net/ethtool/ts.h
index d901a879a671..ab9805308353 100644
--- a/net/ethtool/ts.h
+++ b/net/ethtool/ts.h

@@ -5,9 +5,15 @@
  
  #include "netlink.h"
  
+/* phc_index is an int and -1 means no PHC, so keep the request non-negative */
+static const struct netlink_range_validation ethnl_ts_prov_index_range = {
+	.max = INT_MAX,
+};
+
  static const struct nla_policy
  ethnl_ts_hwtst_prov_policy[ETHTOOL_A_TS_HWTSTAMP_PROVIDER_MAX + 1] = {
-	[ETHTOOL_A_TS_HWTSTAMP_PROVIDER_INDEX] = { .type = NLA_U32 },
+	[ETHTOOL_A_TS_HWTSTAMP_PROVIDER_INDEX] =
+		NLA_POLICY_FULL_RANGE(NLA_U32, &ethnl_ts_prov_index_range),
  	[ETHTOOL_A_TS_HWTSTAMP_PROVIDER_QUALIFIER] =
  		NLA_POLICY_MAX(NLA_U32, HWTSTAMP_PROVIDER_QUALIFIER_CNT - 1)
  };