Re: [PATCH v2 3/4] arch: copy_thread: pass clone_flags as u64

[Guo Ren <guoren@kernel.org>]

On Mon, Sep 1, 2025 at 9:10 PM Simon Schuster via B4 Relay
<devnull+schuster.simon.siemens-energy.com@kernel.org> wrote:
>
> From: Simon Schuster <schuster.simon@siemens-energy.com>
>
> With the introduction of clone3 in commit 7f192e3cd316 ("fork: add
> clone3") the effective bit width of clone_flags on all architectures was
> increased from 32-bit to 64-bit, with a new type of u64 for the flags.
> However, for most consumers of clone_flags the interface was not
> changed from the previous type of unsigned long.
>
> While this works fine as long as none of the new 64-bit flag bits
> (CLONE_CLEAR_SIGHAND and CLONE_INTO_CGROUP) are evaluated, this is still
> undesirable in terms of the principle of least surprise.
>
> Thus, this commit fixes all relevant interfaces of the copy_thread
> function that is called from copy_process to consistently pass
> clone_flags as u64, so that no truncation to 32-bit integers occurs on
> 32-bit architectures.
>
> Signed-off-by: Simon Schuster <schuster.simon@siemens-energy.com>
> ---
>  arch/alpha/kernel/process.c      | 2 +-
>  arch/arc/kernel/process.c        | 2 +-
>  arch/arm/kernel/process.c        | 2 +-
>  arch/arm64/kernel/process.c      | 2 +-
>  arch/csky/kernel/process.c       | 2 +-
>  arch/hexagon/kernel/process.c    | 2 +-
>  arch/loongarch/kernel/process.c  | 2 +-
>  arch/m68k/kernel/process.c       | 2 +-
>  arch/microblaze/kernel/process.c | 2 +-
>  arch/mips/kernel/process.c       | 2 +-
>  arch/nios2/kernel/process.c      | 2 +-
>  arch/openrisc/kernel/process.c   | 2 +-
>  arch/parisc/kernel/process.c     | 2 +-
>  arch/powerpc/kernel/process.c    | 2 +-
>  arch/riscv/kernel/process.c      | 2 +-
>  arch/s390/kernel/process.c       | 2 +-
>  arch/sh/kernel/process_32.c      | 2 +-
>  arch/sparc/kernel/process_32.c   | 2 +-
>  arch/sparc/kernel/process_64.c   | 2 +-
>  arch/um/kernel/process.c         | 2 +-
>  arch/x86/include/asm/fpu/sched.h | 2 +-
>  arch/x86/include/asm/shstk.h     | 4 ++--
>  arch/x86/kernel/fpu/core.c       | 2 +-
>  arch/x86/kernel/process.c        | 2 +-
>  arch/x86/kernel/shstk.c          | 2 +-
>  arch/xtensa/kernel/process.c     | 2 +-
>  26 files changed, 27 insertions(+), 27 deletions(-)
>
> diff --git a/arch/alpha/kernel/process.c b/arch/alpha/kernel/process.c
> index 582d96548385..06522451f018 100644
> --- a/arch/alpha/kernel/process.c
> +++ b/arch/alpha/kernel/process.c
> @@ -231,7 +231,7 @@ flush_thread(void)
>   */
>  int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
>  {
> -       unsigned long clone_flags = args->flags;
> +       u64 clone_flags = args->flags;
>         unsigned long usp = args->stack;
>         unsigned long tls = args->tls;
>         extern void ret_from_fork(void);
> diff --git a/arch/arc/kernel/process.c b/arch/arc/kernel/process.c
> index 186ceab661eb..8166d0908713 100644
> --- a/arch/arc/kernel/process.c
> +++ b/arch/arc/kernel/process.c
> @@ -166,7 +166,7 @@ asmlinkage void ret_from_fork(void);
>   */
>  int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
>  {
> -       unsigned long clone_flags = args->flags;
> +       u64 clone_flags = args->flags;
>         unsigned long usp = args->stack;
>         unsigned long tls = args->tls;
>         struct pt_regs *c_regs;        /* child's pt_regs */
> diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
> index e16ed102960c..d7aa95225c70 100644
> --- a/arch/arm/kernel/process.c
> +++ b/arch/arm/kernel/process.c
> @@ -234,7 +234,7 @@ asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
>
>  int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
>  {
> -       unsigned long clone_flags = args->flags;
> +       u64 clone_flags = args->flags;
>         unsigned long stack_start = args->stack;
>         unsigned long tls = args->tls;
>         struct thread_info *thread = task_thread_info(p);
> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> index 96482a1412c6..fba7ca102a8c 100644
> --- a/arch/arm64/kernel/process.c
> +++ b/arch/arm64/kernel/process.c
> @@ -409,7 +409,7 @@ asmlinkage void ret_from_fork(void) asm("ret_from_fork");
>
>  int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
>  {
> -       unsigned long clone_flags = args->flags;
> +       u64 clone_flags = args->flags;
>         unsigned long stack_start = args->stack;
>         unsigned long tls = args->tls;
>         struct pt_regs *childregs = task_pt_regs(p);
> diff --git a/arch/csky/kernel/process.c b/arch/csky/kernel/process.c
> index 0c6e4b17fe00..a7a90340042a 100644
> --- a/arch/csky/kernel/process.c
> +++ b/arch/csky/kernel/process.c
> @@ -32,7 +32,7 @@ void flush_thread(void){}
>
>  int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
>  {
> -       unsigned long clone_flags = args->flags;
> +       u64 clone_flags = args->flags;
Acked-by: Guo Ren (Alibaba Damo Academy) <guoren@kernel.org>

>         unsigned long usp = args->stack;
>         unsigned long tls = args->tls;
>         struct switch_stack *childstack;
> diff --git a/arch/hexagon/kernel/process.c b/arch/hexagon/kernel/process.c
> index 2a77bfd75694..15b4992bfa29 100644
> --- a/arch/hexagon/kernel/process.c
> +++ b/arch/hexagon/kernel/process.c
> @@ -52,7 +52,7 @@ void arch_cpu_idle(void)
>   */
>  int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
>  {
> -       unsigned long clone_flags = args->flags;
> +       u64 clone_flags = args->flags;
>         unsigned long usp = args->stack;
>         unsigned long tls = args->tls;
>         struct thread_info *ti = task_thread_info(p);
> diff --git a/arch/loongarch/kernel/process.c b/arch/loongarch/kernel/process.c
> index 3582f591bab2..efd9edf65603 100644
> --- a/arch/loongarch/kernel/process.c
> +++ b/arch/loongarch/kernel/process.c
> @@ -167,7 +167,7 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
>         unsigned long childksp;
>         unsigned long tls = args->tls;
>         unsigned long usp = args->stack;
> -       unsigned long clone_flags = args->flags;
> +       u64 clone_flags = args->flags;
>         struct pt_regs *childregs, *regs = current_pt_regs();
>
>         childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE;
> diff --git a/arch/m68k/kernel/process.c b/arch/m68k/kernel/process.c
> index fda7eac23f87..f5a07a70e938 100644
> --- a/arch/m68k/kernel/process.c
> +++ b/arch/m68k/kernel/process.c
> @@ -141,7 +141,7 @@ asmlinkage int m68k_clone3(struct pt_regs *regs)
>
>  int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
>  {
> -       unsigned long clone_flags = args->flags;
> +       u64 clone_flags = args->flags;
>         unsigned long usp = args->stack;
>         unsigned long tls = args->tls;
>         struct fork_frame {
> diff --git a/arch/microblaze/kernel/process.c b/arch/microblaze/kernel/process.c
> index 56342e11442d..6cbf642d7b80 100644
> --- a/arch/microblaze/kernel/process.c
> +++ b/arch/microblaze/kernel/process.c
> @@ -54,7 +54,7 @@ void flush_thread(void)
>
>  int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
>  {
> -       unsigned long clone_flags = args->flags;
> +       u64 clone_flags = args->flags;
>         unsigned long usp = args->stack;
>         unsigned long tls = args->tls;
>         struct pt_regs *childregs = task_pt_regs(p);
> diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
> index 02aa6a04a21d..29191fa1801e 100644
> --- a/arch/mips/kernel/process.c
> +++ b/arch/mips/kernel/process.c
> @@ -107,7 +107,7 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
>   */
>  int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
>  {
> -       unsigned long clone_flags = args->flags;
> +       u64 clone_flags = args->flags;
>         unsigned long usp = args->stack;
>         unsigned long tls = args->tls;
>         struct thread_info *ti = task_thread_info(p);
> diff --git a/arch/nios2/kernel/process.c b/arch/nios2/kernel/process.c
> index f84021303f6a..151404139085 100644
> --- a/arch/nios2/kernel/process.c
> +++ b/arch/nios2/kernel/process.c
> @@ -101,7 +101,7 @@ void flush_thread(void)
>
>  int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
>  {
> -       unsigned long clone_flags = args->flags;
> +       u64 clone_flags = args->flags;
>         unsigned long usp = args->stack;
>         unsigned long tls = args->tls;
>         struct pt_regs *childregs = task_pt_regs(p);
> diff --git a/arch/openrisc/kernel/process.c b/arch/openrisc/kernel/process.c
> index eef99fee2110..73ffb9fa3118 100644
> --- a/arch/openrisc/kernel/process.c
> +++ b/arch/openrisc/kernel/process.c
> @@ -165,7 +165,7 @@ extern asmlinkage void ret_from_fork(void);
>  int
>  copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
>  {
> -       unsigned long clone_flags = args->flags;
> +       u64 clone_flags = args->flags;
>         unsigned long usp = args->stack;
>         unsigned long tls = args->tls;
>         struct pt_regs *userregs;
> diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c
> index ed93bd8c1545..e64ab5d2a40d 100644
> --- a/arch/parisc/kernel/process.c
> +++ b/arch/parisc/kernel/process.c
> @@ -201,7 +201,7 @@ arch_initcall(parisc_idle_init);
>  int
>  copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
>  {
> -       unsigned long clone_flags = args->flags;
> +       u64 clone_flags = args->flags;
>         unsigned long usp = args->stack;
>         unsigned long tls = args->tls;
>         struct pt_regs *cregs = &(p->thread.regs);
> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> index 855e09886503..eb23966ac0a9 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -1805,7 +1805,7 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
>                         f = ret_from_kernel_user_thread;
>                 } else {
>                         struct pt_regs *regs = current_pt_regs();
> -                       unsigned long clone_flags = args->flags;
> +                       u64 clone_flags = args->flags;
>                         unsigned long usp = args->stack;
>
>                         /* Copy registers */
> diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
> index a0a40889d79a..31a392993cb4 100644
> --- a/arch/riscv/kernel/process.c
> +++ b/arch/riscv/kernel/process.c
> @@ -223,7 +223,7 @@ asmlinkage void ret_from_fork_user(struct pt_regs *regs)
>
>  int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
>  {
> -       unsigned long clone_flags = args->flags;
> +       u64 clone_flags = args->flags;
>         unsigned long usp = args->stack;
>         unsigned long tls = args->tls;
>         struct pt_regs *childregs = task_pt_regs(p);
> diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c
> index f55f09cda6f8..b107dbca4ed7 100644
> --- a/arch/s390/kernel/process.c
> +++ b/arch/s390/kernel/process.c
> @@ -106,7 +106,7 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
>
>  int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
>  {
> -       unsigned long clone_flags = args->flags;
> +       u64 clone_flags = args->flags;
>         unsigned long new_stackp = args->stack;
>         unsigned long tls = args->tls;
>         struct fake_frame
> diff --git a/arch/sh/kernel/process_32.c b/arch/sh/kernel/process_32.c
> index 92b6649d4929..62f753a85b89 100644
> --- a/arch/sh/kernel/process_32.c
> +++ b/arch/sh/kernel/process_32.c
> @@ -89,7 +89,7 @@ asmlinkage void ret_from_kernel_thread(void);
>
>  int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
>  {
> -       unsigned long clone_flags = args->flags;
> +       u64 clone_flags = args->flags;
>         unsigned long usp = args->stack;
>         unsigned long tls = args->tls;
>         struct thread_info *ti = task_thread_info(p);
> diff --git a/arch/sparc/kernel/process_32.c b/arch/sparc/kernel/process_32.c
> index 9c7c662cb565..5a28c0e91bf1 100644
> --- a/arch/sparc/kernel/process_32.c
> +++ b/arch/sparc/kernel/process_32.c
> @@ -260,7 +260,7 @@ extern void ret_from_kernel_thread(void);
>
>  int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
>  {
> -       unsigned long clone_flags = args->flags;
> +       u64 clone_flags = args->flags;
>         unsigned long sp = args->stack;
>         unsigned long tls = args->tls;
>         struct thread_info *ti = task_thread_info(p);
> diff --git a/arch/sparc/kernel/process_64.c b/arch/sparc/kernel/process_64.c
> index 529adfecd58c..25781923788a 100644
> --- a/arch/sparc/kernel/process_64.c
> +++ b/arch/sparc/kernel/process_64.c
> @@ -567,7 +567,7 @@ void fault_in_user_windows(struct pt_regs *regs)
>   */
>  int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
>  {
> -       unsigned long clone_flags = args->flags;
> +       u64 clone_flags = args->flags;
>         unsigned long sp = args->stack;
>         unsigned long tls = args->tls;
>         struct thread_info *t = task_thread_info(p);
> diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
> index 1be644de9e41..9c9c66dc45f0 100644
> --- a/arch/um/kernel/process.c
> +++ b/arch/um/kernel/process.c
> @@ -143,7 +143,7 @@ static void fork_handler(void)
>
>  int copy_thread(struct task_struct * p, const struct kernel_clone_args *args)
>  {
> -       unsigned long clone_flags = args->flags;
> +       u64 clone_flags = args->flags;
>         unsigned long sp = args->stack;
>         unsigned long tls = args->tls;
>         void (*handler)(void);
> diff --git a/arch/x86/include/asm/fpu/sched.h b/arch/x86/include/asm/fpu/sched.h
> index c060549c6c94..89004f4ca208 100644
> --- a/arch/x86/include/asm/fpu/sched.h
> +++ b/arch/x86/include/asm/fpu/sched.h
> @@ -11,7 +11,7 @@
>
>  extern void save_fpregs_to_fpstate(struct fpu *fpu);
>  extern void fpu__drop(struct task_struct *tsk);
> -extern int  fpu_clone(struct task_struct *dst, unsigned long clone_flags, bool minimal,
> +extern int  fpu_clone(struct task_struct *dst, u64 clone_flags, bool minimal,
>                       unsigned long shstk_addr);
>  extern void fpu_flush_thread(void);
>
> diff --git a/arch/x86/include/asm/shstk.h b/arch/x86/include/asm/shstk.h
> index ba6f2fe43848..0f50e0125943 100644
> --- a/arch/x86/include/asm/shstk.h
> +++ b/arch/x86/include/asm/shstk.h
> @@ -16,7 +16,7 @@ struct thread_shstk {
>
>  long shstk_prctl(struct task_struct *task, int option, unsigned long arg2);
>  void reset_thread_features(void);
> -unsigned long shstk_alloc_thread_stack(struct task_struct *p, unsigned long clone_flags,
> +unsigned long shstk_alloc_thread_stack(struct task_struct *p, u64 clone_flags,
>                                        unsigned long stack_size);
>  void shstk_free(struct task_struct *p);
>  int setup_signal_shadow_stack(struct ksignal *ksig);
> @@ -28,7 +28,7 @@ static inline long shstk_prctl(struct task_struct *task, int option,
>                                unsigned long arg2) { return -EINVAL; }
>  static inline void reset_thread_features(void) {}
>  static inline unsigned long shstk_alloc_thread_stack(struct task_struct *p,
> -                                                    unsigned long clone_flags,
> +                                                    u64 clone_flags,
>                                                      unsigned long stack_size) { return 0; }
>  static inline void shstk_free(struct task_struct *p) {}
>  static inline int setup_signal_shadow_stack(struct ksignal *ksig) { return 0; }
> diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
> index aefd412a23dc..1f71cc135e9a 100644
> --- a/arch/x86/kernel/fpu/core.c
> +++ b/arch/x86/kernel/fpu/core.c
> @@ -631,7 +631,7 @@ static int update_fpu_shstk(struct task_struct *dst, unsigned long ssp)
>  }
>
>  /* Clone current's FPU state on fork */
> -int fpu_clone(struct task_struct *dst, unsigned long clone_flags, bool minimal,
> +int fpu_clone(struct task_struct *dst, u64 clone_flags, bool minimal,
>               unsigned long ssp)
>  {
>         /*
> diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
> index 1b7960cf6eb0..e3a3987b0c4f 100644
> --- a/arch/x86/kernel/process.c
> +++ b/arch/x86/kernel/process.c
> @@ -159,7 +159,7 @@ __visible void ret_from_fork(struct task_struct *prev, struct pt_regs *regs,
>
>  int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
>  {
> -       unsigned long clone_flags = args->flags;
> +       u64 clone_flags = args->flags;
>         unsigned long sp = args->stack;
>         unsigned long tls = args->tls;
>         struct inactive_task_frame *frame;
> diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c
> index 2ddf23387c7e..5eba6c5a6775 100644
> --- a/arch/x86/kernel/shstk.c
> +++ b/arch/x86/kernel/shstk.c
> @@ -191,7 +191,7 @@ void reset_thread_features(void)
>         current->thread.features_locked = 0;
>  }
>
> -unsigned long shstk_alloc_thread_stack(struct task_struct *tsk, unsigned long clone_flags,
> +unsigned long shstk_alloc_thread_stack(struct task_struct *tsk, u64 clone_flags,
>                                        unsigned long stack_size)
>  {
>         struct thread_shstk *shstk = &tsk->thread.shstk;
> diff --git a/arch/xtensa/kernel/process.c b/arch/xtensa/kernel/process.c
> index 7bd66677f7b6..94d43f44be13 100644
> --- a/arch/xtensa/kernel/process.c
> +++ b/arch/xtensa/kernel/process.c
> @@ -267,7 +267,7 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
>
>  int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
>  {
> -       unsigned long clone_flags = args->flags;
> +       u64 clone_flags = args->flags;
>         unsigned long usp_thread_fn = args->stack;
>         unsigned long tls = args->tls;
>         struct pt_regs *childregs = task_pt_regs(p);
>
> --
> 2.39.5
>
>


-- 
Best Regards
 Guo Ren