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

From: Mike Rapoport <rppt@kernel.org>
To: 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>,
	David Hildenbrand <david@redhat.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>,
	Mike Rapoport <rppt@kernel.org>,
	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: [PATCH] memfd_secret: use unsigned int rather than long as syscall flags type
Date: Wed, 31 Mar 2021 17:23:45 +0300	[thread overview]
Message-ID: <20210331142345.27532-1-rppt@kernel.org> (raw)

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);
 }
-- 
2.28.0

