2021-03-31 14:27:44

by Mike Rapoport

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

From: Mike Rapoport <[email protected]>

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 <[email protected]>
---

@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

2021-03-31 14:55:35

by David Hildenbrand

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 <[email protected]>
>
> 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 <[email protected]>
> ---
>
> @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

2021-03-31 21:54:56

by Yury Norov

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

On Wed, Mar 31, 2021 at 05:23:45PM +0300, Mike Rapoport wrote:
> From: Mike Rapoport <[email protected]>
>
> 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 <[email protected]>

Acked-by: Yury Norov <[email protected]>