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This set of changes updates init and user mode helper tasks to be

Browse Source 
ordinary user mode tasks.
 
 In commit 40966e316f ("kthread: Ensure struct kthread is present for
 all kthreads") caused init and the user mode helper threads that call
 kernel_execve to have struct kthread allocated for them.  This struct
 kthread going away during execve in turned made a use after free of
 struct kthread possible.
 
 The commit 343f4c49f2 ("kthread: Don't allocate kthread_struct for
 init and umh") is enough to fix the use after free and is simple enough
 to be backportable.
 
 The rest of the changes pass struct kernel_clone_args to clean things
 up and cause the code to make sense.
 
 In making init and the user mode helpers tasks purely user mode tasks
 I ran into two complications.  The function task_tick_numa was
 detecting tasks without an mm by testing for the presence of
 PF_KTHREAD.  The initramfs code in populate_initrd_image was using
 flush_delayed_fput to ensuere the closing of all it's file descriptors
 was complete, and flush_delayed_fput does not work in a userspace thread.
 
 I have looked and looked and more complications and in my code review
 I have not found any, and neither has anyone else with the code sitting
 in linux-next.
 
 Link: https://lkml.kernel.org/r/87mtfu4up3.fsf@email.froward.int.ebiederm.org
 
 Eric W. Biederman (8):
       kthread: Don't allocate kthread_struct for init and umh
       fork: Pass struct kernel_clone_args into copy_thread
       fork: Explicity test for idle tasks in copy_thread
       fork: Generalize PF_IO_WORKER handling
       init: Deal with the init process being a user mode process
       fork: Explicitly set PF_KTHREAD
       fork: Stop allowing kthreads to call execve
       sched: Update task_tick_numa to ignore tasks without an mm
 
  arch/alpha/kernel/process.c      | 13 ++++++------
  arch/arc/kernel/process.c        | 13 ++++++------
  arch/arm/kernel/process.c        | 12 ++++++-----
  arch/arm64/kernel/process.c      | 12 ++++++-----
  arch/csky/kernel/process.c       | 15 ++++++-------
  arch/h8300/kernel/process.c      | 10 ++++-----
  arch/hexagon/kernel/process.c    | 12 ++++++-----
  arch/ia64/kernel/process.c       | 15 +++++++------
  arch/m68k/kernel/process.c       | 12 ++++++-----
  arch/microblaze/kernel/process.c | 12 ++++++-----
  arch/mips/kernel/process.c       | 13 ++++++------
  arch/nios2/kernel/process.c      | 12 ++++++-----
  arch/openrisc/kernel/process.c   | 12 ++++++-----
  arch/parisc/kernel/process.c     | 18 +++++++++-------
  arch/powerpc/kernel/process.c    | 15 +++++++------
  arch/riscv/kernel/process.c      | 12 ++++++-----
  arch/s390/kernel/process.c       | 12 ++++++-----
  arch/sh/kernel/process_32.c      | 12 ++++++-----
  arch/sparc/kernel/process_32.c   | 12 ++++++-----
  arch/sparc/kernel/process_64.c   | 12 ++++++-----
  arch/um/kernel/process.c         | 15 +++++++------
  arch/x86/include/asm/fpu/sched.h |  2 +-
  arch/x86/include/asm/switch_to.h |  8 +++----
  arch/x86/kernel/fpu/core.c       |  4 ++--
  arch/x86/kernel/process.c        | 18 +++++++++-------
  arch/xtensa/kernel/process.c     | 17 ++++++++-------
  fs/exec.c                        |  8 ++++---
  include/linux/sched/task.h       |  8 +++++--
  init/initramfs.c                 |  2 ++
  init/main.c                      |  2 +-
  kernel/fork.c                    | 46 +++++++++++++++++++++++++++++++++-------
  kernel/sched/fair.c              |  2 +-
  kernel/umh.c                     |  6 +++---
  33 files changed, 234 insertions(+), 160 deletions(-)
 
 Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Merge tag 'kthread-cleanups-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

Pull kthread updates from Eric Biederman:
 "This updates init and user mode helper tasks to be ordinary user mode
  tasks.

  Commit 40966e316f ("kthread: Ensure struct kthread is present for
  all kthreads") caused init and the user mode helper threads that call
  kernel_execve to have struct kthread allocated for them. This struct
  kthread going away during execve in turned made a use after free of
  struct kthread possible.

  Here, commit 343f4c49f2 ("kthread: Don't allocate kthread_struct for
  init and umh") is enough to fix the use after free and is simple
  enough to be backportable.

  The rest of the changes pass struct kernel_clone_args to clean things
  up and cause the code to make sense.

  In making init and the user mode helpers tasks purely user mode tasks
  I ran into two complications. The function task_tick_numa was
  detecting tasks without an mm by testing for the presence of
  PF_KTHREAD. The initramfs code in populate_initrd_image was using
  flush_delayed_fput to ensuere the closing of all it's file descriptors
  was complete, and flush_delayed_fput does not work in a userspace
  thread.

  I have looked and looked and more complications and in my code review
  I have not found any, and neither has anyone else with the code
  sitting in linux-next"

* tag 'kthread-cleanups-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  sched: Update task_tick_numa to ignore tasks without an mm
  fork: Stop allowing kthreads to call execve
  fork: Explicitly set PF_KTHREAD
  init: Deal with the init process being a user mode process
  fork: Generalize PF_IO_WORKER handling
  fork: Explicity test for idle tasks in copy_thread
  fork: Pass struct kernel_clone_args into copy_thread
  kthread: Don't allocate kthread_struct for init and umh
This commit is contained in:
Linus Torvalds 2022-06-03 16:03:05 -07:00
commit 1ec6574a3c
32 changed files with 229 additions and 155 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
arch/alpha/kernel/process.c
View File

@ -233,10 +233,11 @@ release_thread(struct task_struct *dead_task)
/*
* Copy architecture-specific thread state
*/
int copy_thread(unsigned long clone_flags, unsigned long usp,
unsigned long kthread_arg, struct task_struct *p,
unsigned long tls)
int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
unsigned long clone_flags = args->flags;
unsigned long usp = args->stack;
unsigned long tls = args->tls;
extern void ret_from_fork(void);
extern void ret_from_kernel_thread(void);
@ -249,13 +250,13 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
childti->pcb.ksp = (unsigned long) childstack;
childti->pcb.flags = 1; /* set FEN, clear everything else */
if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
if (unlikely(args->fn)) {
/* kernel thread */
memset(childstack, 0,
sizeof(struct switch_stack) + sizeof(struct pt_regs));
childstack->r26 = (unsigned long) ret_from_kernel_thread;
childstack->r9 = usp; /* function */
childstack->r10 = kthread_arg;
childstack->r9 = (unsigned long) args->fn;
childstack->r10 = (unsigned long) args->fn_arg;
childregs->hae = alpha_mv.hae_cache;
childti->pcb.usp = 0;
return 0;

13
arch/arc/kernel/process.c
View File

@ -162,10 +162,11 @@ asmlinkage void ret_from_fork(void);
* | user_r25 |
* ------------------ <===== END of PAGE
*/
int copy_thread(unsigned long clone_flags, unsigned long usp,
unsigned long kthread_arg, struct task_struct *p,
unsigned long tls)
int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
unsigned long clone_flags = args->flags;
unsigned long usp = args->stack;
unsigned long tls = args->tls;
struct pt_regs *c_regs; /* child's pt_regs */
unsigned long *childksp; /* to unwind out of __switch_to() */
struct callee_regs *c_callee; /* child's callee regs */
@ -191,11 +192,11 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
childksp[0] = 0; /* fp */
childksp[1] = (unsigned long)ret_from_fork; /* blink */
if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
if (unlikely(args->fn)) {
memset(c_regs, 0, sizeof(struct pt_regs));
c_callee->r13 = kthread_arg;
c_callee->r14 = usp; /* function */
c_callee->r13 = (unsigned long)args->fn_arg;
c_callee->r14 = (unsigned long)args->fn;
return 0;
}

12
arch/arm/kernel/process.c
View File

@ -238,9 +238,11 @@ void release_thread(struct task_struct *dead_task)
asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
int copy_thread(unsigned long clone_flags, unsigned long stack_start,
unsigned long stk_sz, struct task_struct *p, unsigned long tls)
int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
unsigned long clone_flags = args->flags;
unsigned long stack_start = args->stack;
unsigned long tls = args->tls;
struct thread_info *thread = task_thread_info(p);
struct pt_regs *childregs = task_pt_regs(p);
@ -256,15 +258,15 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start,
thread->cpu_domain = get_domain();
#endif
if (likely(!(p->flags & (PF_KTHREAD | PF_IO_WORKER)))) {
if (likely(!args->fn)) {
*childregs = *current_pt_regs();
childregs->ARM_r0 = 0;
if (stack_start)
childregs->ARM_sp = stack_start;
} else {
memset(childregs, 0, sizeof(struct pt_regs));
thread->cpu_context.r4 = stk_sz;
thread->cpu_context.r5 = stack_start;
thread->cpu_context.r4 = (unsigned long)args->fn_arg;
thread->cpu_context.r5 = (unsigned long)args->fn;
childregs->ARM_cpsr = SVC_MODE;
}
thread->cpu_context.pc = (unsigned long)ret_from_fork;

12
arch/arm64/kernel/process.c
View File

@ -343,9 +343,11 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
asmlinkage void ret_from_fork(void) asm("ret_from_fork");
int copy_thread(unsigned long clone_flags, unsigned long stack_start,
unsigned long stk_sz, struct task_struct *p, unsigned long tls)
int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
unsigned long clone_flags = args->flags;
unsigned long stack_start = args->stack;
unsigned long tls = args->tls;
struct pt_regs *childregs = task_pt_regs(p);
memset(&p->thread.cpu_context, 0, sizeof(struct cpu_context));
@ -361,7 +363,7 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start,
ptrauth_thread_init_kernel(p);
if (likely(!(p->flags & (PF_KTHREAD | PF_IO_WORKER)))) {
if (likely(!args->fn)) {
*childregs = *current_pt_regs();
childregs->regs[0] = 0;
@ -399,8 +401,8 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start,
memset(childregs, 0, sizeof(struct pt_regs));
childregs->pstate = PSR_MODE_EL1h | PSR_IL_BIT;
p->thread.cpu_context.x19 = stack_start;
p->thread.cpu_context.x20 = stk_sz;
p->thread.cpu_context.x19 = (unsigned long)args->fn;
p->thread.cpu_context.x20 = (unsigned long)args->fn_arg;
}
p->thread.cpu_context.pc = (unsigned long)ret_from_fork;
p->thread.cpu_context.sp = (unsigned long)childregs;

15
arch/csky/kernel/process.c
View File

@ -29,12 +29,11 @@ asmlinkage void ret_from_kernel_thread(void);
*/
void flush_thread(void){}
int copy_thread(unsigned long clone_flags,
unsigned long usp,
unsigned long kthread_arg,
struct task_struct *p,
unsigned long tls)
int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
unsigned long clone_flags = args->flags;
unsigned long usp = args->stack;
unsigned long tls = args->tls;
struct switch_stack *childstack;
struct pt_regs *childregs = task_pt_regs(p);
@ -48,11 +47,11 @@ int copy_thread(unsigned long clone_flags,
/* setup thread.sp for switch_to !!! */
p->thread.sp = (unsigned long)childstack;
if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
if (unlikely(args->fn)) {
memset(childregs, 0, sizeof(struct pt_regs));
childstack->r15 = (unsigned long) ret_from_kernel_thread;
childstack->r10 = kthread_arg;
childstack->r9 = usp;
childstack->r10 = (unsigned long) args->fn_arg;
childstack->r9 = (unsigned long) args->fn;
childregs->sr = mfcr("psr");
} else {
*childregs = *(current_pt_regs());

12
arch/hexagon/kernel/process.c
View File

@ -50,9 +50,11 @@ void arch_cpu_idle(void)
/*
* Copy architecture-specific thread state
*/
int copy_thread(unsigned long clone_flags, unsigned long usp, unsigned long arg,
struct task_struct *p, unsigned long tls)
int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
unsigned long clone_flags = args->flags;
unsigned long usp = args->stack;
unsigned long tls = args->tls;
struct thread_info *ti = task_thread_info(p);
struct hexagon_switch_stack *ss;
struct pt_regs *childregs;
@ -73,11 +75,11 @@ int copy_thread(unsigned long clone_flags, unsigned long usp, unsigned long arg,
sizeof(*ss));
ss->lr = (unsigned long)ret_from_fork;
p->thread.switch_sp = ss;
if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
if (unlikely(args->fn)) {
memset(childregs, 0, sizeof(struct pt_regs));
/* r24 <- fn, r25 <- arg */
ss->r24 = usp;
ss->r25 = arg;
ss->r24 = (unsigned long)args->fn;
ss->r25 = (unsigned long)args->fn_arg;
pt_set_kmode(childregs);
return 0;
}

15
arch/ia64/kernel/process.c
View File

@ -296,9 +296,12 @@ ia64_load_extra (struct task_struct *task)
* so there is nothing to worry about.
*/
int
copy_thread(unsigned long clone_flags, unsigned long user_stack_base,
unsigned long user_stack_size, struct task_struct *p, unsigned long tls)
copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
unsigned long clone_flags = args->flags;
unsigned long user_stack_base = args->stack;
unsigned long user_stack_size = args->stack_size;
unsigned long tls = args->tls;
extern char ia64_ret_from_clone;
struct switch_stack *child_stack, *stack;
unsigned long rbs, child_rbs, rbs_size;
@ -339,14 +342,14 @@ copy_thread(unsigned long clone_flags, unsigned long user_stack_base,
ia64_drop_fpu(p); /* don't pick up stale state from a CPU's fph */
if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
if (unlikely(!user_stack_base)) {
if (unlikely(args->fn)) {
if (unlikely(args->idle)) {
/* fork_idle() called us */
return 0;
}
memset(child_stack, 0, sizeof(*child_ptregs) + sizeof(*child_stack));
child_stack->r4 = user_stack_base; /* payload */
child_stack->r5 = user_stack_size; /* argument */
child_stack->r4 = (unsigned long) args->fn;
child_stack->r5 = (unsigned long) args->fn_arg;
/*
* Preserve PSR bits, except for bits 32-34 and 37-45,
* which we can't read.

12
arch/m68k/kernel/process.c
View File

@ -137,9 +137,11 @@ asmlinkage int m68k_clone3(struct pt_regs *regs)
return sys_clone3((struct clone_args __user *)regs->d1, regs->d2);
}
int copy_thread(unsigned long clone_flags, unsigned long usp, unsigned long arg,
struct task_struct *p, unsigned long tls)
int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
unsigned long clone_flags = args->flags;
unsigned long usp = args->stack;
unsigned long tls = args->tls;
struct fork_frame {
struct switch_stack sw;
struct pt_regs regs;
@ -156,12 +158,12 @@ int copy_thread(unsigned long clone_flags, unsigned long usp, unsigned long arg,
*/
p->thread.fc = USER_DATA;
if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
if (unlikely(args->fn)) {
/* kernel thread */
memset(frame, 0, sizeof(struct fork_frame));
frame->regs.sr = PS_S;
frame->sw.a3 = usp; /* function */
frame->sw.d7 = arg;
frame->sw.a3 = (unsigned long)args->fn;
frame->sw.d7 = (unsigned long)args->fn_arg;
frame->sw.retpc = (unsigned long)ret_from_kernel_thread;
p->thread.usp = 0;
return 0;

12
arch/microblaze/kernel/process.c
View File

@ -52,20 +52,22 @@ void flush_thread(void)
{
}
int copy_thread(unsigned long clone_flags, unsigned long usp, unsigned long arg,
struct task_struct *p, unsigned long tls)
int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
unsigned long clone_flags = args->flags;
unsigned long usp = args->stack;
unsigned long tls = args->tls;
struct pt_regs *childregs = task_pt_regs(p);
struct thread_info *ti = task_thread_info(p);
if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
if (unlikely(args->fn)) {
/* if we're creating a new kernel thread then just zeroing all
* the registers. That's OK for a brand new thread.*/
memset(childregs, 0, sizeof(struct pt_regs));
memset(&ti->cpu_context, 0, sizeof(struct cpu_context));
ti->cpu_context.r1 = (unsigned long)childregs;
ti->cpu_context.r20 = (unsigned long)usp; /* fn */
ti->cpu_context.r19 = (unsigned long)arg;
ti->cpu_context.r20 = (unsigned long)args->fn;
ti->cpu_context.r19 = (unsigned long)args->fn_arg;
childregs->pt_mode = 1;
local_save_flags(childregs->msr);
ti->cpu_context.msr = childregs->msr & ~MSR_IE;

13
arch/mips/kernel/process.c
View File

@ -105,10 +105,11 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
/*
* Copy architecture-specific thread state
*/
int copy_thread(unsigned long clone_flags, unsigned long usp,
unsigned long kthread_arg, struct task_struct *p,
unsigned long tls)
int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
unsigned long clone_flags = args->flags;
unsigned long usp = args->stack;
unsigned long tls = args->tls;
struct thread_info *ti = task_thread_info(p);
struct pt_regs *childregs, *regs = current_pt_regs();
unsigned long childksp;
@ -120,12 +121,12 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
/* Put the stack after the struct pt_regs. */
childksp = (unsigned long) childregs;
p->thread.cp0_status = (read_c0_status() & ~(ST0_CU2|ST0_CU1)) | ST0_KERNEL_CUMASK;
if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
if (unlikely(args->fn)) {
/* kernel thread */
unsigned long status = p->thread.cp0_status;
memset(childregs, 0, sizeof(struct pt_regs));
p->thread.reg16 = usp; /* fn */
p->thread.reg17 = kthread_arg;
p->thread.reg16 = (unsigned long)args->fn;
p->thread.reg17 = (unsigned long)args->fn_arg;
p->thread.reg29 = childksp;
p->thread.reg31 = (unsigned long) ret_from_kernel_thread;
#if defined(CONFIG_CPU_R3000)

12
arch/nios2/kernel/process.c
View File

@ -100,21 +100,23 @@ void flush_thread(void)
{
}
int copy_thread(unsigned long clone_flags, unsigned long usp, unsigned long arg,
struct task_struct *p, unsigned long tls)
int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
unsigned long clone_flags = args->flags;
unsigned long usp = args->stack;
unsigned long tls = args->tls;
struct pt_regs *childregs = task_pt_regs(p);
struct pt_regs *regs;
struct switch_stack *stack;
struct switch_stack *childstack =
((struct switch_stack *)childregs) - 1;
if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
if (unlikely(args->fn)) {
memset(childstack, 0,
sizeof(struct switch_stack) + sizeof(struct pt_regs));
childstack->r16 = usp; /* fn */
childstack->r17 = arg;
childstack->r16 = (unsigned long) args->fn;
childstack->r17 = (unsigned long) args->fn_arg;
childstack->ra = (unsigned long) ret_from_kernel_thread;
childregs->estatus = STATUS_PIE;
childregs->sp = (unsigned long) childstack;

12
arch/openrisc/kernel/process.c
View File

@ -167,9 +167,11 @@ extern asmlinkage void ret_from_fork(void);
*/
int
copy_thread(unsigned long clone_flags, unsigned long usp, unsigned long arg,
struct task_struct *p, unsigned long tls)
copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
unsigned long clone_flags = args->flags;
unsigned long usp = args->stack;
unsigned long tls = args->tls;
struct pt_regs *userregs;
struct pt_regs *kregs;
unsigned long sp = (unsigned long)task_stack_page(p) + THREAD_SIZE;
@ -187,10 +189,10 @@ copy_thread(unsigned long clone_flags, unsigned long usp, unsigned long arg,
sp -= sizeof(struct pt_regs);
kregs = (struct pt_regs *)sp;
if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
if (unlikely(args->fn)) {
memset(kregs, 0, sizeof(struct pt_regs));
kregs->gpr[20] = usp; /* fn, kernel thread */
kregs->gpr[22] = arg;
kregs->gpr[20] = (unsigned long)args->fn;
kregs->gpr[22] = (unsigned long)args->fn_arg;
} else {
*userregs = *current_pt_regs();

18
arch/parisc/kernel/process.c
View File

@ -206,9 +206,11 @@ arch_initcall(parisc_idle_init);
* Copy architecture-specific thread state
*/
int
copy_thread(unsigned long clone_flags, unsigned long usp,
unsigned long kthread_arg, struct task_struct *p, unsigned long tls)
copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
unsigned long clone_flags = args->flags;
unsigned long usp = args->stack;
unsigned long tls = args->tls;
struct pt_regs *cregs = &(p->thread.regs);
void *stack = task_stack_page(p);
@ -218,10 +220,10 @@ copy_thread(unsigned long clone_flags, unsigned long usp,
extern void * const ret_from_kernel_thread;
extern void * const child_return;
if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
if (unlikely(args->fn)) {
/* kernel thread */
memset(cregs, 0, sizeof(struct pt_regs));
if (!usp) /* idle thread */
if (args->idle) /* idle thread */
return 0;
/* Must exit via ret_from_kernel_thread in order
* to call schedule_tail()
@ -233,12 +235,12 @@ copy_thread(unsigned long clone_flags, unsigned long usp,
* ret_from_kernel_thread.
*/
#ifdef CONFIG_64BIT
cregs->gr[27] = ((unsigned long *)usp)[3];
cregs->gr[26] = ((unsigned long *)usp)[2];
cregs->gr[27] = ((unsigned long *)args->fn)[3];
cregs->gr[26] = ((unsigned long *)args->fn)[2];
#else
cregs->gr[26] = usp;
cregs->gr[26] = (unsigned long) args->fn;
#endif
cregs->gr[25] = kthread_arg;
cregs->gr[25] = (unsigned long) args->fn_arg;
} else {
/* user thread */
/* usp must be word aligned. This also prevents users from

15
arch/powerpc/kernel/process.c
View File

@ -1713,10 +1713,11 @@ static void setup_ksp_vsid(struct task_struct *p, unsigned long sp)
/*
* Copy architecture-specific thread state
*/
int copy_thread(unsigned long clone_flags, unsigned long usp,
unsigned long kthread_arg, struct task_struct *p,
unsigned long tls)
int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
unsigned long clone_flags = args->flags;
unsigned long usp = args->stack;
unsigned long tls = args->tls;
struct pt_regs *childregs, *kregs;
extern void ret_from_fork(void);
extern void ret_from_fork_scv(void);
@ -1733,18 +1734,18 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
/* Copy registers */
sp -= sizeof(struct pt_regs);
childregs = (struct pt_regs *) sp;
if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
if (unlikely(args->fn)) {
/* kernel thread */
memset(childregs, 0, sizeof(struct pt_regs));
childregs->gpr[1] = sp + sizeof(struct pt_regs);
/* function */
if (usp)
childregs->gpr[14] = ppc_function_entry((void *)usp);
if (args->fn)
childregs->gpr[14] = ppc_function_entry((void *)args->fn);
#ifdef CONFIG_PPC64
clear_tsk_thread_flag(p, TIF_32BIT);
childregs->softe = IRQS_ENABLED;
#endif
childregs->gpr[15] = kthread_arg;
childregs->gpr[15] = (unsigned long)args->fn_arg;
p->thread.regs = NULL; /* no user register state */
ti->flags |= _TIF_RESTOREALL;
f = ret_from_kernel_thread;

12
arch/riscv/kernel/process.c
View File

@ -157,13 +157,15 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
return 0;
}
int copy_thread(unsigned long clone_flags, unsigned long usp, unsigned long arg,
struct task_struct *p, unsigned long tls)
int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
unsigned long clone_flags = args->flags;
unsigned long usp = args->stack;
unsigned long tls = args->tls;
struct pt_regs *childregs = task_pt_regs(p);
/* p->thread holds context to be restored by __switch_to() */
if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
if (unlikely(args->fn)) {
/* Kernel thread */
memset(childregs, 0, sizeof(struct pt_regs));
childregs->gp = gp_in_global;
@ -171,8 +173,8 @@ int copy_thread(unsigned long clone_flags, unsigned long usp, unsigned long arg,
childregs->status = SR_PP | SR_PIE;
p->thread.ra = (unsigned long)ret_from_kernel_thread;
p->thread.s[0] = usp; /* fn */
p->thread.s[1] = arg;
p->thread.s[0] = (unsigned long)args->fn;
p->thread.s[1] = (unsigned long)args->fn_arg;
} else {
*childregs = *(current_pt_regs());
if (usp) /* User fork */

12
arch/s390/kernel/process.c
View File

@ -94,9 +94,11 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
return 0;
}
int copy_thread(unsigned long clone_flags, unsigned long new_stackp,
unsigned long arg, struct task_struct *p, unsigned long tls)
int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
unsigned long clone_flags = args->flags;
unsigned long new_stackp = args->stack;
unsigned long tls = args->tls;
struct fake_frame
{
struct stack_frame sf;
@ -130,15 +132,15 @@ int copy_thread(unsigned long clone_flags, unsigned long new_stackp,
frame->sf.gprs[9] = (unsigned long)frame;
/* Store access registers to kernel stack of new process. */
if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
if (unlikely(args->fn)) {
/* kernel thread */
memset(&frame->childregs, 0, sizeof(struct pt_regs));
frame->childregs.psw.mask = PSW_KERNEL_BITS | PSW_MASK_DAT |
PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK;
frame->childregs.psw.addr =
(unsigned long)__ret_from_fork;
frame->childregs.gprs[9] = new_stackp; /* function */
frame->childregs.gprs[10] = arg;
frame->childregs.gprs[9] = (unsigned long)args->fn;
frame->childregs.gprs[10] = (unsigned long)args->fn_arg;
frame->childregs.orig_gpr2 = -1;
frame->childregs.last_break = 1;
return 0;

12
arch/sh/kernel/process_32.c
View File

@ -92,9 +92,11 @@ void release_thread(struct task_struct *dead_task)
asmlinkage void ret_from_fork(void);
asmlinkage void ret_from_kernel_thread(void);
int copy_thread(unsigned long clone_flags, unsigned long usp, unsigned long arg,
struct task_struct *p, unsigned long tls)
int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
unsigned long clone_flags = args->flags;
unsigned long usp = args->stack;
unsigned long tls = args->tls;
struct thread_info *ti = task_thread_info(p);
struct pt_regs *childregs;
@ -114,11 +116,11 @@ int copy_thread(unsigned long clone_flags, unsigned long usp, unsigned long arg,
childregs = task_pt_regs(p);
p->thread.sp = (unsigned long) childregs;
if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
if (unlikely(args->fn)) {
memset(childregs, 0, sizeof(struct pt_regs));
p->thread.pc = (unsigned long) ret_from_kernel_thread;
childregs->regs[4] = arg;
childregs->regs[5] = usp;
childregs->regs[4] = (unsigned long) args->fn_arg;
childregs->regs[5] = (unsigned long) args->fn;
childregs->sr = SR_MD;
#if defined(CONFIG_SH_FPU)
childregs->sr |= SR_FD;

12
arch/sparc/kernel/process_32.c
View File

@ -259,9 +259,11 @@ clone_stackframe(struct sparc_stackf __user *dst,
extern void ret_from_fork(void);
extern void ret_from_kernel_thread(void);
int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg,
struct task_struct *p, unsigned long tls)
int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
unsigned long clone_flags = args->flags;
unsigned long sp = args->stack;
unsigned long tls = args->tls;
struct thread_info *ti = task_thread_info(p);
struct pt_regs *childregs, *regs = current_pt_regs();
char *new_stack;
@ -296,13 +298,13 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg,
ti->ksp = (unsigned long) new_stack;
p->thread.kregs = childregs;
if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
if (unlikely(args->fn)) {
extern int nwindows;
unsigned long psr;
memset(new_stack, 0, STACKFRAME_SZ + TRACEREG_SZ);
ti->kpc = (((unsigned long) ret_from_kernel_thread) - 0x8);
childregs->u_regs[UREG_G1] = sp; /* function */
childregs->u_regs[UREG_G2] = arg;
childregs->u_regs[UREG_G1] = (unsigned long) args->fn;
childregs->u_regs[UREG_G2] = (unsigned long) args->fn_arg;
psr = childregs->psr = get_psr();
ti->kpsr = psr | PSR_PIL;
ti->kwim = 1 << (((psr & PSR_CWP) + 1) % nwindows);

12
arch/sparc/kernel/process_64.c
View File

@ -564,9 +564,11 @@ barf:
* Parent --> %o0 == childs pid, %o1 == 0
* Child --> %o0 == parents pid, %o1 == 1
*/
int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg,
struct task_struct *p, unsigned long tls)
int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
unsigned long clone_flags = args->flags;
unsigned long sp = args->stack;
unsigned long tls = args->tls;
struct thread_info *t = task_thread_info(p);
struct pt_regs *regs = current_pt_regs();
struct sparc_stackf *parent_sf;
@ -584,12 +586,12 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg,
sizeof(struct sparc_stackf));
t->fpsaved[0] = 0;
if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
if (unlikely(args->fn)) {
memset(child_trap_frame, 0, child_stack_sz);
__thread_flag_byte_ptr(t)[TI_FLAG_BYTE_CWP] =
(current_pt_regs()->tstate + 1) & TSTATE_CWP;
t->kregs->u_regs[UREG_G1] = sp; /* function */
t->kregs->u_regs[UREG_G2] = arg;
t->kregs->u_regs[UREG_G1] = (unsigned long) args->fn;
t->kregs->u_regs[UREG_G2] = (unsigned long) args->fn_arg;
return 0;
}

15
arch/um/kernel/process.c
View File

@ -154,16 +154,17 @@ void fork_handler(void)
userspace(&current->thread.regs.regs, current_thread_info()->aux_fp_regs);
}
int copy_thread(unsigned long clone_flags, unsigned long sp,
unsigned long arg, struct task_struct * p, unsigned long tls)
int copy_thread(struct task_struct * p, const struct kernel_clone_args *args)
{
unsigned long clone_flags = args->flags;
unsigned long sp = args->stack;
unsigned long tls = args->tls;
void (*handler)(void);
int kthread = current->flags & (PF_KTHREAD | PF_IO_WORKER);
int ret = 0;
p->thread = (struct thread_struct) INIT_THREAD;
if (!kthread) {
if (!args->fn) {
memcpy(&p->thread.regs.regs, current_pt_regs(),
sizeof(p->thread.regs.regs));
PT_REGS_SET_SYSCALL_RETURN(&p->thread.regs, 0);
@ -175,14 +176,14 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
arch_copy_thread(&current->thread.arch, &p->thread.arch);
} else {
get_safe_registers(p->thread.regs.regs.gp, p->thread.regs.regs.fp);
p->thread.request.u.thread.proc = (int (*)(void *))sp;
p->thread.request.u.thread.arg = (void *)arg;
p->thread.request.u.thread.proc = args->fn;
p->thread.request.u.thread.arg = args->fn_arg;
handler = new_thread_handler;
}
new_thread(task_stack_page(p), &p->thread.switch_buf, handler);
if (!kthread) {
if (!args->fn) {
clear_flushed_tls(p);
/*

2
arch/x86/include/asm/fpu/sched.h
View File

@ -11,7 +11,7 @@
extern void save_fpregs_to_fpstate(struct fpu *fpu);
extern void fpu__drop(struct fpu *fpu);
extern int fpu_clone(struct task_struct *dst, unsigned long clone_flags);
extern int fpu_clone(struct task_struct *dst, unsigned long clone_flags, bool minimal);
extern void fpu_flush_thread(void);
/*

8
arch/x86/include/asm/switch_to.h
View File

@ -78,13 +78,13 @@ static inline void update_task_stack(struct task_struct *task)
}
static inline void kthread_frame_init(struct inactive_task_frame *frame,
unsigned long fun, unsigned long arg)
int (*fun)(void *), void *arg)
{
frame->bx = fun;
frame->bx = (unsigned long)fun;
#ifdef CONFIG_X86_32
frame->di = arg;
frame->di = (unsigned long)arg;
#else
frame->r12 = arg;
frame->r12 = (unsigned long)arg;
#endif
}

4
arch/x86/kernel/fpu/core.c
View File

@ -556,7 +556,7 @@ static inline void fpu_inherit_perms(struct fpu *dst_fpu)
}
/* Clone current's FPU state on fork */
int fpu_clone(struct task_struct *dst, unsigned long clone_flags)
int fpu_clone(struct task_struct *dst, unsigned long clone_flags, bool minimal)
{
struct fpu *src_fpu = &current->thread.fpu;
struct fpu *dst_fpu = &dst->thread.fpu;
@ -579,7 +579,7 @@ int fpu_clone(struct task_struct *dst, unsigned long clone_flags)
* No FPU state inheritance for kernel threads and IO
* worker threads.
*/
if (dst->flags & (PF_KTHREAD | PF_IO_WORKER)) {
if (minimal) {
/* Clear out the minimal state */
memcpy(&dst_fpu->fpstate->regs, &init_fpstate.regs,
init_fpstate_copy_size());

18
arch/x86/kernel/process.c
View File

@ -131,9 +131,11 @@ static int set_new_tls(struct task_struct *p, unsigned long tls)
return do_set_thread_area_64(p, ARCH_SET_FS, tls);
}
int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg,
struct task_struct *p, unsigned long tls)
int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
unsigned long clone_flags = args->flags;
unsigned long sp = args->stack;
unsigned long tls = args->tls;
struct inactive_task_frame *frame;
struct fork_frame *fork_frame;
struct pt_regs *childregs;
@ -171,13 +173,13 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg,
frame->flags = X86_EFLAGS_FIXED;
#endif
fpu_clone(p, clone_flags);
fpu_clone(p, clone_flags, args->fn);
/* Kernel thread ? */
if (unlikely(p->flags & PF_KTHREAD)) {
p->thread.pkru = pkru_get_init_value();
memset(childregs, 0, sizeof(struct pt_regs));
kthread_frame_init(frame, sp, arg);
kthread_frame_init(frame, args->fn, args->fn_arg);
return 0;
}
@ -193,10 +195,10 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg,
if (sp)
childregs->sp = sp;
if (unlikely(p->flags & PF_IO_WORKER)) {
if (unlikely(args->fn)) {
/*
* An IO thread is a user space thread, but it doesn't
* return to ret_after_fork().
* A user space thread, but it doesn't return to
* ret_after_fork().
*
* In order to indicate that to tools like gdb,
* we reset the stack and instruction pointers.
@ -206,7 +208,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg,
*/
childregs->sp = 0;
childregs->ip = 0;
kthread_frame_init(frame, sp, arg);
kthread_frame_init(frame, args->fn, args->fn_arg);
return 0;
}

17
arch/xtensa/kernel/process.c
View File

@ -263,10 +263,11 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
* involved. Much simpler to just not copy those live frames across.
*/
int copy_thread(unsigned long clone_flags, unsigned long usp_thread_fn,
unsigned long thread_fn_arg, struct task_struct *p,
unsigned long tls)
int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
unsigned long clone_flags = args->flags;
unsigned long usp_thread_fn = args->stack;
unsigned long tls = args->tls;
struct pt_regs *childregs = task_pt_regs(p);
#if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS)
@ -286,7 +287,7 @@ int copy_thread(unsigned long clone_flags, unsigned long usp_thread_fn,
#error Unsupported Xtensa ABI
#endif
if (!(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
if (!args->fn) {
struct pt_regs *regs = current_pt_regs();
unsigned long usp = usp_thread_fn ?
usp_thread_fn : regs->areg[1];
@ -338,15 +339,15 @@ int copy_thread(unsigned long clone_flags, unsigned long usp_thread_fn,
* Window underflow will load registers from the
* spill slots on the stack on return from _switch_to.
*/
SPILL_SLOT(childregs, 2) = usp_thread_fn;
SPILL_SLOT(childregs, 3) = thread_fn_arg;
SPILL_SLOT(childregs, 2) = (unsigned long)args->fn;
SPILL_SLOT(childregs, 3) = (unsigned long)args->fn_arg;
#elif defined(__XTENSA_CALL0_ABI__)
/*
* a12 = thread_fn, a13 = thread_fn arg.
* _switch_to epilogue will load registers from the stack.
*/
((unsigned long *)p->thread.sp)[0] = usp_thread_fn;
((unsigned long *)p->thread.sp)[1] = thread_fn_arg;
((unsigned long *)p->thread.sp)[0] = (unsigned long)args->fn;
((unsigned long *)p->thread.sp)[1] = (unsigned long)args->fn_arg;
#else
#error Unsupported Xtensa ABI
#endif

8
fs/exec.c
View File

@ -1312,9 +1312,7 @@ int begin_new_exec(struct linux_binprm * bprm)
if (retval)
goto out_unlock;
if (me->flags & PF_KTHREAD)
free_kthread_struct(me);
me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC |
PF_NOFREEZE | PF_NO_SETAFFINITY);
flush_thread();
me->personality &= ~bprm->per_clear;
@ -1959,6 +1957,10 @@ int kernel_execve(const char *kernel_filename,
int fd = AT_FDCWD;
int retval;
/* It is non-sense for kernel threads to call execve */
if (WARN_ON_ONCE(current->flags & PF_KTHREAD))
return -EINVAL;
filename = getname_kernel(kernel_filename);
if (IS_ERR(filename))
return PTR_ERR(filename);

8
include/linux/sched/task.h
View File

@ -32,6 +32,10 @@ struct kernel_clone_args {
size_t set_tid_size;
int cgroup;
int io_thread;
int kthread;
int idle;
int (*fn)(void *);
void *fn_arg;
struct cgroup *cgrp;
struct css_set *cset;
};
@ -67,8 +71,7 @@ extern void fork_init(void);
extern void release_task(struct task_struct * p);
extern int copy_thread(unsigned long, unsigned long, unsigned long,
struct task_struct *, unsigned long);
extern int copy_thread(struct task_struct *, const struct kernel_clone_args *);
extern void flush_thread(void);
@ -89,6 +92,7 @@ struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node);
struct task_struct *fork_idle(int);
struct mm_struct *copy_init_mm(void);
extern pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags);
extern pid_t user_mode_thread(int (*fn)(void *), void *arg, unsigned long flags);
extern long kernel_wait4(pid_t, int __user *, int, struct rusage *);
int kernel_wait(pid_t pid, int *stat);

2
init/initramfs.c
View File

@ -15,6 +15,7 @@
#include <linux/mm.h>
#include <linux/namei.h>
#include <linux/init_syscalls.h>
#include <linux/task_work.h>
#include <linux/umh.h>
static __initdata bool csum_present;
@ -727,6 +728,7 @@ done:
initrd_end = 0;
flush_delayed_fput();
task_work_run();
}
static ASYNC_DOMAIN_EXCLUSIVE(initramfs_domain);

2
init/main.c
View File

@ -688,7 +688,7 @@ noinline void __ref rest_init(void)
* the init task will end up wanting to create kthreads, which, if
* we schedule it before we create kthreadd, will OOPS.
*/
pid = kernel_thread(kernel_init, NULL, CLONE_FS);
pid = user_mode_thread(kernel_init, NULL, CLONE_FS);
/*
* Pin init on the boot CPU. Task migration is not properly working
* until sched_init_smp() has been run. It will set the allowed

46
kernel/fork.c
View File

@ -1982,7 +1982,7 @@ static __latent_entropy struct task_struct *copy_process(
struct task_struct *p;
struct multiprocess_signals delayed;
struct file *pidfile = NULL;
u64 clone_flags = args->flags;
const u64 clone_flags = args->flags;
struct nsproxy *nsp = current->nsproxy;
/*
@ -2071,6 +2071,9 @@ static __latent_entropy struct task_struct *copy_process(
p = dup_task_struct(current, node);
if (!p)
goto fork_out;
p->flags &= ~PF_KTHREAD;
if (args->kthread)
p->flags |= PF_KTHREAD;
if (args->io_thread) {
/*
* Mark us an IO worker, and block any signal that isn't
@ -2160,7 +2163,7 @@ static __latent_entropy struct task_struct *copy_process(
p->io_context = NULL;
audit_set_context(p, NULL);
cgroup_fork(p);
if (p->flags & PF_KTHREAD) {
if (args->kthread) {
if (!set_kthread_struct(p))
goto bad_fork_cleanup_delayacct;
}
@ -2243,7 +2246,7 @@ static __latent_entropy struct task_struct *copy_process(
retval = copy_io(clone_flags, p);
if (retval)
goto bad_fork_cleanup_namespaces;
retval = copy_thread(clone_flags, args->stack, args->stack_size, p, args->tls);
retval = copy_thread(p, args);
if (retval)
goto bad_fork_cleanup_io;
@ -2547,11 +2550,21 @@ static inline void init_idle_pids(struct task_struct *idle)
}
}
static int idle_dummy(void *dummy)
{
/* This function is never called */
return 0;
}
struct task_struct * __init fork_idle(int cpu)
{
struct task_struct *task;
struct kernel_clone_args args = {
.flags = CLONE_VM,
.flags = CLONE_VM,
.fn = &idle_dummy,
.fn_arg = NULL,
.kthread = 1,
.idle = 1,
};
task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args);
@ -2582,8 +2595,8 @@ struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
.flags = ((lower_32_bits(flags) | CLONE_VM |
CLONE_UNTRACED) & ~CSIGNAL),
.exit_signal = (lower_32_bits(flags) & CSIGNAL),
.stack = (unsigned long)fn,
.stack_size = (unsigned long)arg,
.fn = fn,
.fn_arg = arg,
.io_thread = 1,
};
@ -2687,8 +2700,25 @@ pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
.flags = ((lower_32_bits(flags) | CLONE_VM |
CLONE_UNTRACED) & ~CSIGNAL),
.exit_signal = (lower_32_bits(flags) & CSIGNAL),
.stack = (unsigned long)fn,
.stack_size = (unsigned long)arg,
.fn = fn,
.fn_arg = arg,
.kthread = 1,
};
return kernel_clone(&args);
}
/*
* Create a user mode thread.
*/
pid_t user_mode_thread(int (*fn)(void *), void *arg, unsigned long flags)
{
struct kernel_clone_args args = {
.flags = ((lower_32_bits(flags) | CLONE_VM |
CLONE_UNTRACED) & ~CSIGNAL),
.exit_signal = (lower_32_bits(flags) & CSIGNAL),
.fn = fn,
.fn_arg = arg,
};
return kernel_clone(&args);

2
kernel/sched/fair.c
View File

@ -2927,7 +2927,7 @@ static void task_tick_numa(struct rq *rq, struct task_struct *curr)
/*
* We don't care about NUMA placement if we don't have memory.
*/
if ((curr->flags & (PF_EXITING | PF_KTHREAD)) || work->next != work)
if (!curr->mm || (curr->flags & (PF_EXITING | PF_KTHREAD)) || work->next != work)
return;
/*

6
kernel/umh.c
View File

@ -132,7 +132,7 @@ static void call_usermodehelper_exec_sync(struct subprocess_info *sub_info)
/* If SIGCLD is ignored do_wait won't populate the status. */
kernel_sigaction(SIGCHLD, SIG_DFL);
pid = kernel_thread(call_usermodehelper_exec_async, sub_info, SIGCHLD);
pid = user_mode_thread(call_usermodehelper_exec_async, sub_info, SIGCHLD);
if (pid < 0)
sub_info->retval = pid;
else
@ -171,8 +171,8 @@ static void call_usermodehelper_exec_work(struct work_struct *work)
* want to pollute current->children, and we need a parent
* that always ignores SIGCHLD to ensure auto-reaping.
*/
pid = kernel_thread(call_usermodehelper_exec_async, sub_info,
CLONE_PARENT | SIGCHLD);
pid = user_mode_thread(call_usermodehelper_exec_async, sub_info,
CLONE_PARENT | SIGCHLD);
if (pid < 0) {
sub_info->retval = pid;
umh_complete(sub_info);