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Date: Fri, 25 Sep 2026 16:07:21 +0200
From: Nicolai Buchwitz <nb@tipi-net.de>
To: Kory Maincent <kory.maincent@bootlin.com>
Cc: Andrew Lunn <andrew@lunn.ch>, Jakub Kicinski <kuba@kernel.org>, "David
 S. Miller" <davem@davemloft.net>, Eric Dumazet <edumazet@kernel.org>, Paolo
 Abeni <pabeni@redhat.com>, Simon Horman <horms@kernel.org>, Vadim Fedorenko
 <vadim.fedorenko@linux.dev>, Maxime Chevallier
 <maxime.chevallier@bootlin.com>, netdev@vger.kernel.org,
 linux-kernel@vger.kernel.org
Subject: Re: [PATCH net v3 1/2] net: ethtool: reject an out of range hwtstamp
 provider index
In-Reply-To: <0ddf8280-0a66-4dbf-9195-1b90e97015c5@bootlin.com>
References: <20260925135237.3432266-1-nb@tipi-net.de>
 <20260925135237.3432266-2-nb@tipi-net.de>
 <0ddf8280-0a66-4dbf-9195-1b90e97015c5@bootlin.com>
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Hi Kory

On 25.9.2026 15:55, Kory Maincent wrote:

> [...]

>>   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)
>>   };
> 
> I think you can simply do this:
> [ETHTOOL_A_TS_HWTSTAMP_PROVIDER_INDEX] =
> 	NLA_POLICY_MAX(NLA_U32, INT_MAX),

That was my initial thought, but unfortunately it doesn't work. struct 
nla_policy's
.max is s16 and INT_MAX is truncated to -1. It ends up as U64_MAX in the 
range check
and in the end nothing gets rejected.

     include/vdso/limits.h:8:25: warning: overflow in conversion from 
'int'
     to 'short int' changes value from '2147483647' to '-1' [-Woverflow]

> [...]

Thanks,
Nicolai