linux-kernel - Re: [PATCH] memfd_secret: use unsigned int rather than long as syscall flags type

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Message-ID: <516d5d41-8d4a-7519-e88e-e16747e993c9@redhat.com>
Date:   Wed, 31 Mar 2021 16:53:16 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Mike Rapoport <rppt@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Christopher Lameter <cl@...ux.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Elena Reshetova <elena.reshetova@...el.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        James Bottomley <jejb@...ux.ibm.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Matthew Wilcox <willy@...radead.org>,
        Matthew Garrett <mjg59@...f.ucam.org>,
        Mark Rutland <mark.rutland@....com>,
        Michal Hocko <mhocko@...e.com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Roman Gushchin <guro@...com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Shuah Khan <shuah@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tycho Andersen <tycho@...ho.ws>, Will Deacon <will@...nel.org>,
        Yury Norov <yury.norov@...il.com>, linux-api@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-riscv@...ts.infradead.org,
        x86@...nel.org
Subject: Re: [PATCH] memfd_secret: use unsigned int rather than long as
 syscall flags type

On 31.03.21 16:23, Mike Rapoport wrote:
> From: Mike Rapoport <rppt@...ux.ibm.com>
> 
> Yuri Norov says:
> 
>    If parameter size is the same for native and compat ABIs, we may
>    wire a syscall made by compat client to native handler. This is
>    true for unsigned int, but not true for unsigned long or pointer.
> 
>    That's why I suggest using unsigned int and so avoid creating compat
>    entry point.
> 
> Use unsigned int as the type of the flags parameter in memfd_secret()
> system call.
> 
> Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>
> ---
> 
> @Andrew,
> The patch is vs v5.12-rc5-mmots-2021-03-30-23, I'd appreciate if it would
> be added as a fixup to the memfd_secret series.
> 
>   include/linux/syscalls.h                  | 2 +-
>   mm/secretmem.c                            | 2 +-
>   tools/testing/selftests/vm/memfd_secret.c | 2 +-
>   3 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
> index 49c93c906893..1a1b5d724497 100644
> --- a/include/linux/syscalls.h
> +++ b/include/linux/syscalls.h
> @@ -1050,7 +1050,7 @@ asmlinkage long sys_landlock_create_ruleset(const struct landlock_ruleset_attr _
>   asmlinkage long sys_landlock_add_rule(int ruleset_fd, enum landlock_rule_type rule_type,
>   		const void __user *rule_attr, __u32 flags);
>   asmlinkage long sys_landlock_restrict_self(int ruleset_fd, __u32 flags);
> -asmlinkage long sys_memfd_secret(unsigned long flags);
> +asmlinkage long sys_memfd_secret(unsigned int flags);
>   
>   /*
>    * Architecture-specific system calls
> diff --git a/mm/secretmem.c b/mm/secretmem.c
> index f2ae3f32a193..3b1ba3991964 100644
> --- a/mm/secretmem.c
> +++ b/mm/secretmem.c
> @@ -199,7 +199,7 @@ static struct file *secretmem_file_create(unsigned long flags)
>   	return file;
>   }
>   
> -SYSCALL_DEFINE1(memfd_secret, unsigned long, flags)
> +SYSCALL_DEFINE1(memfd_secret, unsigned int, flags)
>   {
>   	struct file *file;
>   	int fd, err;
> diff --git a/tools/testing/selftests/vm/memfd_secret.c b/tools/testing/selftests/vm/memfd_secret.c
> index c878c2b841fc..2462f52e9c96 100644
> --- a/tools/testing/selftests/vm/memfd_secret.c
> +++ b/tools/testing/selftests/vm/memfd_secret.c
> @@ -38,7 +38,7 @@ static unsigned long page_size;
>   static unsigned long mlock_limit_cur;
>   static unsigned long mlock_limit_max;
>   
> -static int memfd_secret(unsigned long flags)
> +static int memfd_secret(unsigned int flags)
>   {
>   	return syscall(__NR_memfd_secret, flags);
>   }
> 

LGTM

-- 
Thanks,

David / dhildenb