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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a6d0f186dbsm7175528f8f.26.2025.06.22.09.35.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 22 Jun 2025 09:35:56 -0700 (PDT) Date: Sun, 22 Jun 2025 17:35:54 +0100 From: David Laight To: Christophe Leroy Cc: Michael Ellerman , Nicholas Piggin , Naveen N Rao , Madhavan Srinivasan , Alexander Viro , Christian Brauner , Jan Kara , Thomas Gleixner , Ingo Molnar , Peter Zijlstra , Darren Hart , Davidlohr Bueso , "Andre Almeida" , Andrew Morton , Dave Hansen , Linus Torvalds , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 1/5] uaccess: Add masked_user_{read/write}_access_begin Message-ID: <20250622173554.7f016f96@pumpkin> In-Reply-To: <6fddae0cf0da15a6521bb847b63324b7a2a067b1.1750585239.git.christophe.leroy@csgroup.eu> References: <6fddae0cf0da15a6521bb847b63324b7a2a067b1.1750585239.git.christophe.leroy@csgroup.eu> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Sun, 22 Jun 2025 11:52:39 +0200 Christophe Leroy wrote: > Allthough masked_user_access_begin() seems to only be used when reading > data from user at the moment, introduce masked_user_read_access_begin() > and masked_user_write_access_begin() in order to match > user_read_access_begin() and user_write_access_begin(). > > Have them default to masked_user_access_begin() when they are > not defined. > > Signed-off-by: Christophe Leroy > --- > fs/select.c | 2 +- > include/linux/uaccess.h | 8 ++++++++ > kernel/futex/futex.h | 4 ++-- > lib/strncpy_from_user.c | 2 +- > lib/strnlen_user.c | 2 +- > 5 files changed, 13 insertions(+), 5 deletions(-) > > diff --git a/fs/select.c b/fs/select.c > index 9fb650d03d52..d8547bedf5eb 100644 > --- a/fs/select.c > +++ b/fs/select.c > @@ -777,7 +777,7 @@ static inline int get_sigset_argpack(struct sigset_argpack *to, > // the path is hot enough for overhead of copy_from_user() to matter > if (from) { > if (can_do_masked_user_access()) > - from = masked_user_access_begin(from); > + from = masked_user_read_access_begin(from); > else if (!user_read_access_begin(from, sizeof(*from))) > return -EFAULT; > unsafe_get_user(to->p, &from->p, Efault); > diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h > index 7c06f4795670..682a0cd2fe51 100644 > --- a/include/linux/uaccess.h > +++ b/include/linux/uaccess.h > @@ -41,6 +41,14 @@ > #ifdef masked_user_access_begin > #define can_do_masked_user_access() 1 > #else > #define can_do_masked_user_access() 0 > #define masked_user_access_begin(src) NULL > #define mask_user_address(src) (src) > #endif > > +#ifndef masked_user_write_access_begin > +#define masked_user_write_access_begin masked_user_access_begin > +#endif > +#ifndef masked_user_read_access_begin > +#define masked_user_read_access_begin masked_user_access_begin > +#endif I think that needs merging with the bit above. Perhaps generating something like: #ifdef masked_user_access_begin #define masked_user_read_access_begin masked_user_access_begin #define masked_user_write_access_begin masked_user_access_begin #endif #ifdef masked_user_read_access_begin #define can_do_masked_user_access() 1 #else #define can_do_masked_user_access() 0 #define masked_user_read_access_begin(src) NULL #define masked_user_write_access_begin(src) NULL #define mask_user_address(src) (src) #endif Otherwise you'll have to #define masked_user_access_begin even though it is never used. Two more patches could change x86-64 to define both and then remove the 'then unused' first check - but that has to be for later. David