linux-kernel - Re: [RFC PATCH 1/4] net: introduce get_optlen() and put

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <90334e83-618b-41e0-a35c-9ce8b0d1d990@samba.org>
Date: Tue, 1 Apr 2025 14:22:50 +0200
From: Stefan Metzmacher <metze@...ba.org>
To: Breno Leitao <leitao@...ian.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
 Jens Axboe <axboe@...nel.dk>, Pavel Begunkov <asml.silence@...il.com>,
 Jakub Kicinski <kuba@...nel.org>, Christoph Hellwig <hch@....de>,
 Karsten Keil <isdn@...ux-pingi.de>, Ayush Sawal <ayush.sawal@...lsio.com>,
 Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>,
 Kuniyuki Iwashima <kuniyu@...zon.com>, Willem de Bruijn
 <willemb@...gle.com>, David Ahern <dsahern@...nel.org>,
 Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
 Xin Long <lucien.xin@...il.com>, Neal Cardwell <ncardwell@...gle.com>,
 Joerg Reuter <jreuter@...na.de>, Marcel Holtmann <marcel@...tmann.org>,
 Johan Hedberg <johan.hedberg@...il.com>,
 Luiz Augusto von Dentz <luiz.dentz@...il.com>,
 Oliver Hartkopp <socketcan@...tkopp.net>,
 Marc Kleine-Budde <mkl@...gutronix.de>,
 Robin van der Gracht <robin@...tonic.nl>,
 Oleksij Rempel <o.rempel@...gutronix.de>, kernel@...gutronix.de,
 Alexander Aring <alex.aring@...il.com>,
 Stefan Schmidt <stefan@...enfreihafen.org>,
 Miquel Raynal <miquel.raynal@...tlin.com>,
 Alexandra Winter <wintera@...ux.ibm.com>,
 Thorsten Winkler <twinkler@...ux.ibm.com>,
 James Chapman <jchapman@...alix.com>, Jeremy Kerr <jk@...econstruct.com.au>,
 Matt Johnston <matt@...econstruct.com.au>,
 Matthieu Baerts <matttbe@...nel.org>, Mat Martineau <martineau@...nel.org>,
 Geliang Tang <geliang@...nel.org>, Krzysztof Kozlowski <krzk@...nel.org>,
 Remi Denis-Courmont <courmisch@...il.com>,
 Allison Henderson <allison.henderson@...cle.com>,
 David Howells <dhowells@...hat.com>, Marc Dionne <marc.dionne@...istor.com>,
 Wenjia Zhang <wenjia@...ux.ibm.com>, Jan Karcher <jaka@...ux.ibm.com>,
 "D. Wythe" <alibuda@...ux.alibaba.com>, Tony Lu <tonylu@...ux.alibaba.com>,
 Wen Gu <guwen@...ux.alibaba.com>, Jon Maloy <jmaloy@...hat.com>,
 Boris Pismenny <borisp@...dia.com>, John Fastabend
 <john.fastabend@...il.com>, Stefano Garzarella <sgarzare@...hat.com>,
 Martin Schiller <ms@....tdt.de>, Björn Töpel
 <bjorn@...nel.org>, Magnus Karlsson <magnus.karlsson@...el.com>,
 Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
 Jonathan Lemon <jonathan.lemon@...il.com>,
 Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
 Jesper Dangaard Brouer <hawk@...nel.org>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-sctp@...r.kernel.org,
 linux-hams@...r.kernel.org, linux-bluetooth@...r.kernel.org,
 linux-can@...r.kernel.org, dccp@...r.kernel.org, linux-wpan@...r.kernel.org,
 linux-s390@...r.kernel.org, mptcp@...ts.linux.dev,
 linux-rdma@...r.kernel.org, rds-devel@....oracle.com,
 linux-afs@...ts.infradead.org, tipc-discussion@...ts.sourceforge.net,
 virtualization@...ts.linux.dev, linux-x25@...r.kernel.org,
 bpf@...r.kernel.org, isdn4linux@...tserv.isdn4linux.de,
 io-uring@...r.kernel.org
Subject: Re: [RFC PATCH 1/4] net: introduce get_optlen() and put_optlen()
 helpers

Hello Breno,

> On Mon, Mar 31, 2025 at 10:10:53PM +0200, Stefan Metzmacher wrote:
>> --- a/include/linux/sockptr.h
>> +++ b/include/linux/sockptr.h
>> @@ -169,4 +169,26 @@ static inline int check_zeroed_sockptr(sockptr_t src, size_t offset,
>>   	return memchr_inv(src.kernel + offset, 0, size) == NULL;
>>   }
>>   
>> +#define __check_optlen_t(__optlen)				\
>> +({								\
>> +	int __user *__ptr __maybe_unused = __optlen; 		\
>> +	BUILD_BUG_ON(sizeof(*(__ptr)) != sizeof(int));		\
>> +})
> 
> I am a bit confused about this macro. I understand that this macro's
> goal is to check that __optlen is a pointer to an integer, otherwise
> failed to build.
> 
> It is unclear to me if that is what it does. Let's suppose that __optlen
> is not an integer pointer. Then:
> 
>> int __user *__ptr __maybe_unused = __optlen;
> 
> This will generate a compile failure/warning due invalid casting,
> depending on -Wincompatible-pointer-types.
> 
>> BUILD_BUG_ON(sizeof(*(__ptr)) != sizeof(int));
> 
> Then this comparison will always false, since __ptr is a pointer to int,
> and you are comparing the size of its content with the sizeof(int).

Yes, it redundant in the first patch, it gets little more useful in
the 2nd and 3rd patch.

metze