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Mon, 2 Mar 2026 14:59:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772463556; bh=yLKCSXO+hQApHc+NF2pMZzlTvrx+yrgTZOCdhXU+l+s=; h=Date:Subject:To:References:From:In-Reply-To:From; b=f2NBa7irVPOLjk3WW4SCmf8FWi+7tBJ3LbL5TJX9XKvS1spGkziwe9pGBJY+oqLo7 kA0iGOYvp0cjlRZXL+tt2MqQSyn2cirVYdwLABTi85/4lhjcDbtxxtfNHjPvF07WxM VGhJDv969X+0XD8Ltsk+AXrf1C36RCmK274CzxkNnrnNzf+bfkiSYGN9DW2Q5LeFol 85vi9xmsuMiRcJ/1EsNPNL1+QYTCSEkkbB/fpWUiTL6w5gSJgyz7KbZ7zgfoOhM5xy GUA1X9y6ljSEOT1J2bnp5Y5mMfrMW692fy/GCNHYl8XYEYdmgabRaVoJG4M+mEOaEn 5PRbc9SZdCdXw== Message-ID: Date: Mon, 2 Mar 2026 15:59:04 +0100 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 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/5] uaccess: Fix scoped_user_read_access() for 'pointer to const' To: david.laight.linux@gmail.com, Alexander Viro , Andre Almeida , Andrew Cooper , Christian Borntraeger , Christian Brauner , Christophe Leroy , Darren Hart , Davidlohr Bueso , Heiko Carstens , Jan Kara , Julia Lawall , Linus Torvalds , linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, LKML , Madhavan Srinivasan , Mathieu Desnoyers , Michael Ellerman , Nicholas Piggin , Nicolas Palix , Palmer Dabbelt , Paul Walmsley , Peter Zijlstra , Russell King , Sven Schnelle , Thomas Gleixner , x86@kernel.org, Kees Cook , akpm@linux-foundation.org References: <20260302132755.1475451-1-david.laight.linux@gmail.com> <20260302132755.1475451-2-david.laight.linux@gmail.com> Content-Language: fr-FR From: "Christophe Leroy (CS GROUP)" In-Reply-To: <20260302132755.1475451-2-david.laight.linux@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Le 02/03/2026 à 14:27, david.laight.linux@gmail.com a écrit : > From: David Laight > > If a 'const struct foo __user *ptr' is used for the address passed > to scoped_user_read_access() then you get a warning/error > uaccess.h:691:1: error: initialization discards 'const' qualifier > from pointer target type [-Werror=discarded-qualifiers] > for the > void __user *_tmpptr = __scoped_user_access_begin(mode, uptr, size, elbl) > assignment. > > Fix by using 'auto' for both _tmpptr and the redeclaration of uptr. > Replace the CLASS() with explicit __cleanup() functions on uptr. > > Fixes: e497310b4ffb "(uaccess: Provide scoped user access regions)" > Signed-off-by: David Laight Reviewed-by: Christophe Leroy (CS GROUP) Tested-by: Christophe Leroy (CS GROUP) Can we get this fix merged in 7.0-rc3 so that we can start building 7.1 on top of it ? Thanks Christophe > --- > include/linux/uaccess.h | 54 +++++++++++++++-------------------------- > 1 file changed, 20 insertions(+), 34 deletions(-) > > diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h > index 1f3804245c06..809e4f7dfdbd 100644 > --- a/include/linux/uaccess.h > +++ b/include/linux/uaccess.h > @@ -647,36 +647,22 @@ static inline void user_access_restore(unsigned long flags) { } > /* Define RW variant so the below _mode macro expansion works */ > #define masked_user_rw_access_begin(u) masked_user_access_begin(u) > #define user_rw_access_begin(u, s) user_access_begin(u, s) > -#define user_rw_access_end() user_access_end() > > /* Scoped user access */ > -#define USER_ACCESS_GUARD(_mode) \ > -static __always_inline void __user * \ > -class_user_##_mode##_begin(void __user *ptr) \ > -{ \ > - return ptr; \ > -} \ > - \ > -static __always_inline void \ > -class_user_##_mode##_end(void __user *ptr) \ > -{ \ > - user_##_mode##_access_end(); \ > -} \ > - \ > -DEFINE_CLASS(user_ ##_mode## _access, void __user *, \ > - class_user_##_mode##_end(_T), \ > - class_user_##_mode##_begin(ptr), void __user *ptr) \ > - \ > -static __always_inline class_user_##_mode##_access_t \ > -class_user_##_mode##_access_ptr(void __user *scope) \ > -{ \ > - return scope; \ > -} > > -USER_ACCESS_GUARD(read) > -USER_ACCESS_GUARD(write) > -USER_ACCESS_GUARD(rw) > -#undef USER_ACCESS_GUARD > +/* Cleanup wrapper functions */ > +static __always_inline void __scoped_user_read_access_end(const void *p) > +{ > + user_read_access_end(); > +}; > +static __always_inline void __scoped_user_write_access_end(const void *p) > +{ > + user_write_access_end(); > +}; > +static __always_inline void __scoped_user_rw_access_end(const void *p) > +{ > + user_access_end(); > +}; > > /** > * __scoped_user_access_begin - Start a scoped user access > @@ -750,13 +736,13 @@ USER_ACCESS_GUARD(rw) > * > * Don't use directly. Use scoped_masked_user_$MODE_access() instead. > */ > -#define __scoped_user_access(mode, uptr, size, elbl) \ > -for (bool done = false; !done; done = true) \ > - for (void __user *_tmpptr = __scoped_user_access_begin(mode, uptr, size, elbl); \ > - !done; done = true) \ > - for (CLASS(user_##mode##_access, scope)(_tmpptr); !done; done = true) \ > - /* Force modified pointer usage within the scope */ \ > - for (const typeof(uptr) uptr = _tmpptr; !done; done = true) > +#define __scoped_user_access(mode, uptr, size, elbl) \ > +for (bool done = false; !done; done = true) \ > + for (auto _tmpptr = __scoped_user_access_begin(mode, uptr, size, elbl); \ > + !done; done = true) \ > + /* Force modified pointer usage within the scope */ \ > + for (const auto uptr __cleanup(__scoped_user_##mode##_access_end) = \ > + _tmpptr; !done; done = true) > > /** > * scoped_user_read_access_size - Start a scoped user read access with given size