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

From: David Hildenbrand <david@redhat.com>
To: Mike Rapoport <rppt@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
	Andy Lutomirski <luto@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
	Borislav Petkov <bp@alien8.de>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Christopher Lameter <cl@linux.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Elena Reshetova <elena.reshetova@intel.com>,
	"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
	James Bottomley <jejb@linux.ibm.com>,
	"Kirill A. Shutemov" <kirill@shutemov.name>,
	Matthew Wilcox <willy@infradead.org>,
	Matthew Garrett <mjg59@srcf.ucam.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Michal Hocko <mhocko@suse.com>,
	Mike Rapoport <rppt@linux.ibm.com>,
	Michael Kerrisk <mtk.manpages@gmail.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Peter Zijlstra <peterz@infradead.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Rick Edgecombe <rick.p.edgecombe@intel.com>,
	Roman Gushchin <guro@fb.com>, Shakeel Butt <shakeelb@google.com>,
	Shuah Khan <shuah@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Tycho Andersen <tycho@tycho.ws>, Will Deacon <will@kernel.org>,
	Yury Norov <yury.norov@gmail.com>,
	linux-api@vger.kernel.org, linux-arch@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
	linux-nvdimm@lists.01.org, linux-riscv@lists.infradead.org,
	x86@kernel.org
Subject: Re: [PATCH] memfd_secret: use unsigned int rather than long as syscall flags type
Date: Wed, 31 Mar 2021 16:53:16 +0200	[thread overview]
Message-ID: <516d5d41-8d4a-7519-e88e-e16747e993c9@redhat.com> (raw)
In-Reply-To: <20210331142345.27532-1-rppt@kernel.org>

On 31.03.21 16:23, Mike Rapoport wrote:
> From: Mike Rapoport <rppt@linux.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@linux.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