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

* [PATCH] memfd_secret: use unsigned int rather than long as syscall flags type
@ 2021-03-31 14:23 Mike Rapoport
  2021-03-31 14:53 ` David Hildenbrand
  2021-03-31 21:52 ` Yury Norov
  0 siblings, 2 replies; 3+ messages in thread
From: Mike Rapoport @ 2021-03-31 14:23 UTC (permalink / raw)
  To: Andrew Morton
  Cc: Alexander Viro, Andy Lutomirski, Arnd Bergmann, Borislav Petkov,
	Catalin Marinas, Christopher Lameter, Dave Hansen,
	David Hildenbrand, Elena Reshetova, H. Peter Anvin, Ingo Molnar,
	James Bottomley, Kirill A. Shutemov, Matthew Wilcox,
	Matthew Garrett, Mark Rutland, Michal Hocko, Mike Rapoport,
	Mike Rapoport, Michael Kerrisk, Palmer Dabbelt, Paul Walmsley,
	Peter Zijlstra, Rafael J. Wysocki, Rick Edgecombe,
	Roman Gushchin, Shakeel B utt, Shuah Khan, Thomas Gleixner,
	Tycho Andersen, Will Deacon, Yury Norov, linux-api, linux-arch,
	linux-arm-kernel, linux-fsdevel, linux-mm, linux-kernel,
	linux-kselftest, linux-nvdimm, linux-riscv, x86

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
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