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Miller" , Eric Dumazet , Paolo Abeni , Simon Horman , Kuniyuki Iwashima , Willem de Bruijn , David Ahern , Marcelo Ricardo Leitner , Xin Long , Neal Cardwell , Joerg Reuter , Marcel Holtmann , Johan Hedberg , Luiz Augusto von Dentz , Oliver Hartkopp , Marc Kleine-Budde , Robin van der Gracht , Oleksij Rempel , kernel@pengutronix.de, Alexander Aring , Stefan Schmidt , Miquel Raynal , Alexandra Winter , Thorsten Winkler , James Chapman , Jeremy Kerr , Matt Johnston , Matthieu Baerts , Mat Martineau , Geliang Tang , Krzysztof Kozlowski , Remi Denis-Courmont , Allison Henderson , David Howells , Marc Dionne , Wenjia Zhang , Jan Karcher , "D. Wythe" , Tony Lu , Wen Gu , Jon Maloy , Boris Pismenny , John Fastabend , Stefano Garzarella , Martin Schiller , =?iso-8859-1?Q?Bj=F6rn_T=F6pel?= , Magnus Karlsson , Maciej Fijalkowski , Jonathan Lemon , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-sctp@vger.kernel.org, linux-hams@vger.kernel.org, linux-bluetooth@vger.kernel.org, linux-can@vger.kernel.org, dccp@vger.kernel.org, linux-wpan@vger.kernel.org, linux-s390@vger.kernel.org, mptcp@lists.linux.dev, linux-rdma@vger.kernel.org, rds-devel@oss.oracle.com, linux-afs@lists.infradead.org, tipc-discussion@lists.sourceforge.net, virtualization@lists.linux.dev, linux-x25@vger.kernel.org, bpf@vger.kernel.org, isdn4linux@listserv.isdn4linux.de, io-uring@vger.kernel.org Subject: Re: [RFC PATCH 1/4] net: introduce get_optlen() and put_optlen() helpers Message-ID: References: <156e83128747b2cf7c755bffa68f2519bd255f78.1743449872.git.metze@samba.org> Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <156e83128747b2cf7c755bffa68f2519bd255f78.1743449872.git.metze@samba.org> Hello Stefan, 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).