arm64: sanitize copy_thread(), switch to generic fork/vfork/clone

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/arm64/Kconfig

@@ -33,6 +33,7 @@ config ARM64
 	select RTC_LIB
 	select SPARSE_IRQ
 	select SYSCTL_EXCEPTION_TRACE
+	select CLONE_BACKWARDS
 	help
 	  ARM 64-bit (AArch64) Linux support.
 

arch/arm64/include/asm/syscalls.h

@@ -31,6 +31,8 @@ asmlinkage long sys_sigaltstack_wrapper(const stack_t __user *uss,
  * AArch64 sys_clone implementation has a different prototype than the generic
  * one (additional TLS value argument).
  */
+asmlinkage long sys_clone(unsigned long, unsigned long, void __user *, int,
+	       void __user *);
 #define sys_clone	sys_clone
 
 #include <asm-generic/syscalls.h>

arch/arm64/include/asm/unistd.h

@@ -24,6 +24,9 @@
 #define __ARCH_WANT_SYS_SIGPROCMASK
 #define __ARCH_WANT_COMPAT_SYS_RT_SIGSUSPEND
 #define __ARCH_WANT_COMPAT_SYS_SENDFILE
+#define __ARCH_WANT_SYS_FORK
+#define __ARCH_WANT_SYS_VFORK
 #endif
 #define __ARCH_WANT_SYS_EXECVE
+#define __ARCH_WANT_SYS_CLONE
 #include <uapi/asm/unistd.h>

arch/arm64/include/asm/unistd32.h

@@ -23,7 +23,7 @@
 
 __SYSCALL(0,   sys_restart_syscall)
 __SYSCALL(1,   sys_exit)
-__SYSCALL(2,   compat_sys_fork)
+__SYSCALL(2,   sys_fork)
 __SYSCALL(3,   sys_read)
 __SYSCALL(4,   sys_write)
 __SYSCALL(5,   compat_sys_open)
@@ -211,7 +211,7 @@ __SYSCALL(186, compat_sys_sigaltstack_wrapper)
 __SYSCALL(187, compat_sys_sendfile)
 __SYSCALL(188, sys_ni_syscall)			/* 188 reserved */
 __SYSCALL(189, sys_ni_syscall)			/* 189 reserved */
-__SYSCALL(190, compat_sys_vfork)
+__SYSCALL(190, sys_vfork)
 __SYSCALL(191, compat_sys_getrlimit)		/* SuS compliant getrlimit */
 __SYSCALL(192, sys_mmap_pgoff)
 __SYSCALL(193, compat_sys_truncate64_wrapper)

arch/arm64/kernel/process.c

@@ -235,15 +235,15 @@ 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,
-		struct pt_regs *regs)
+		struct pt_regs *unused)
 {
 	struct pt_regs *childregs = task_pt_regs(p);
 	unsigned long tls = p->thread.tp_value;
 
 	memset(&p->thread.cpu_context, 0, sizeof(struct cpu_context));
 
-	if (likely(regs)) {
-		*childregs = *regs;
+	if (likely(!(p->flags & PF_KTHREAD))) {
+		*childregs = *current_pt_regs();
 		childregs->regs[0] = 0;
 		if (is_compat_thread(task_thread_info(p))) {
 			if (stack_start)
@@ -266,7 +266,7 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start,
 		 * for the new thread.
 		 */
 		if (clone_flags & CLONE_SETTLS)
-			tls = regs->regs[3];
+			tls = childregs->regs[3];
 	} else {
 		memset(childregs, 0, sizeof(struct pt_regs));
 		childregs->pstate = PSR_MODE_EL1h;

arch/arm64/kernel/sys.c

@@ -26,17 +26,6 @@
 #include <linux/slab.h>
 #include <linux/syscalls.h>
 
-/*
- * Clone a task - this clones the calling program thread.
- */
-asmlinkage long sys_clone(unsigned long clone_flags, unsigned long newsp,
-			  int __user *parent_tidptr, unsigned long tls_val,
-			  int __user *child_tidptr)
-{
-	return do_fork(clone_flags, newsp, current_pt_regs(), 0,
-			parent_tidptr, child_tidptr);
-}
-
 asmlinkage long sys_mmap(unsigned long addr, unsigned long len,
 			 unsigned long prot, unsigned long flags,
 			 unsigned long fd, off_t off)

arch/arm64/kernel/sys_compat.c

@@ -28,17 +28,6 @@
 #include <asm/cacheflush.h>
 #include <asm/unistd32.h>
 
-asmlinkage int compat_sys_fork(void)
-{
-	return do_fork(SIGCHLD, 0, current_pt_regs(), 0, NULL, NULL);
-}
-
-asmlinkage int compat_sys_vfork(void)
-{
-	return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
-		       current_pt_regs(), 0, NULL, NULL);
-}
-
 asmlinkage int compat_sys_sched_rr_get_interval(compat_pid_t pid,
 						struct compat_timespec __user *interval)
 {