// SPDX-License-Identifier: GPL-2.0

  /*
   *  linux/kernel/sys.c
   *
   *  Copyright (C) 1991, 1992  Linus Torvalds
   */

  #include <linux/export.h>

  #include <linux/mm.h>
  #include <linux/utsname.h>
  #include <linux/mman.h>

  #include <linux/reboot.h>
  #include <linux/prctl.h>

  #include <linux/highuid.h>
  #include <linux/fs.h>

  #include <linux/kmod.h>

  #include <linux/perf_event.h>

  #include <linux/resource.h>

  #include <linux/kernel.h>

  #include <linux/workqueue.h>

  #include <linux/capability.h>

  #include <linux/device.h>
  #include <linux/key.h>
  #include <linux/times.h>
  #include <linux/posix-timers.h>
  #include <linux/security.h>
  #include <linux/dcookies.h>
  #include <linux/suspend.h>
  #include <linux/tty.h>

  #include <linux/signal.h>

  #include <linux/cn_proc.h>

  #include <linux/getcpu.h>

  #include <linux/task_io_accounting_ops.h>

  #include <linux/seccomp.h>

  #include <linux/cpu.h>

  #include <linux/personality.h>

  #include <linux/ptrace.h>

  #include <linux/fs_struct.h>

  #include <linux/file.h>
  #include <linux/mount.h>

  #include <linux/gfp.h>

  #include <linux/syscore_ops.h>

  #include <linux/version.h>
  #include <linux/ctype.h>

  
  #include <linux/compat.h>
  #include <linux/syscalls.h>

  #include <linux/kprobes.h>

  #include <linux/user_namespace.h>

  #include <linux/binfmts.h>

  #include <linux/sched.h>

  #include <linux/sched/autogroup.h>

  #include <linux/sched/loadavg.h>

  #include <linux/sched/stat.h>

  #include <linux/sched/mm.h>

  #include <linux/sched/coredump.h>

  #include <linux/sched/task.h>

  #include <linux/sched/cputime.h>

  #include <linux/rcupdate.h>
  #include <linux/uidgid.h>
  #include <linux/cred.h>

  #include <linux/nospec.h>

  #include <linux/kmsg_dump.h>

  /* Move somewhere else to avoid recompiling? */
  #include <generated/utsrelease.h>

  #include <linux/uaccess.h>

  #include <asm/io.h>
  #include <asm/unistd.h>
  
  #ifndef SET_UNALIGN_CTL

  # define SET_UNALIGN_CTL(a, b)	(-EINVAL)

  #endif
  #ifndef GET_UNALIGN_CTL

  # define GET_UNALIGN_CTL(a, b)	(-EINVAL)

  #endif
  #ifndef SET_FPEMU_CTL

  # define SET_FPEMU_CTL(a, b)	(-EINVAL)

  #endif
  #ifndef GET_FPEMU_CTL

  # define GET_FPEMU_CTL(a, b)	(-EINVAL)

  #endif
  #ifndef SET_FPEXC_CTL

  # define SET_FPEXC_CTL(a, b)	(-EINVAL)

  #endif
  #ifndef GET_FPEXC_CTL

  # define GET_FPEXC_CTL(a, b)	(-EINVAL)

  #endif

  #ifndef GET_ENDIAN

  # define GET_ENDIAN(a, b)	(-EINVAL)

  #endif
  #ifndef SET_ENDIAN

  # define SET_ENDIAN(a, b)	(-EINVAL)

  #endif

  #ifndef GET_TSC_CTL
  # define GET_TSC_CTL(a)		(-EINVAL)
  #endif
  #ifndef SET_TSC_CTL
  # define SET_TSC_CTL(a)		(-EINVAL)
  #endif

  #ifndef MPX_ENABLE_MANAGEMENT

  # define MPX_ENABLE_MANAGEMENT()	(-EINVAL)

  #endif
  #ifndef MPX_DISABLE_MANAGEMENT

  # define MPX_DISABLE_MANAGEMENT()	(-EINVAL)

  #endif

  #ifndef GET_FP_MODE
  # define GET_FP_MODE(a)		(-EINVAL)
  #endif
  #ifndef SET_FP_MODE
  # define SET_FP_MODE(a,b)	(-EINVAL)
  #endif

  
  /*
   * this is where the system-wide overflow UID and GID are defined, for
   * architectures that now have 32-bit UID/GID but didn't in the past
   */
  
  int overflowuid = DEFAULT_OVERFLOWUID;
  int overflowgid = DEFAULT_OVERFLOWGID;

  EXPORT_SYMBOL(overflowuid);
  EXPORT_SYMBOL(overflowgid);

  
  /*
   * the same as above, but for filesystems which can only store a 16-bit
   * UID and GID. as such, this is needed on all architectures
   */
  
  int fs_overflowuid = DEFAULT_FS_OVERFLOWUID;
  int fs_overflowgid = DEFAULT_FS_OVERFLOWUID;
  
  EXPORT_SYMBOL(fs_overflowuid);
  EXPORT_SYMBOL(fs_overflowgid);
  
  /*

   * Returns true if current's euid is same as p's uid or euid,
   * or has CAP_SYS_NICE to p's user_ns.
   *
   * Called with rcu_read_lock, creds are safe
   */
  static bool set_one_prio_perm(struct task_struct *p)
  {
  	const struct cred *cred = current_cred(), *pcred = __task_cred(p);

  	if (uid_eq(pcred->uid,  cred->euid) ||
  	    uid_eq(pcred->euid, cred->euid))

  		return true;

  	if (ns_capable(pcred->user_ns, CAP_SYS_NICE))

  		return true;
  	return false;
  }
  
  /*

   * set the priority of a task
   * - the caller must hold the RCU read lock
   */

  static int set_one_prio(struct task_struct *p, int niceval, int error)
  {
  	int no_nice;

  	if (!set_one_prio_perm(p)) {

  		error = -EPERM;
  		goto out;
  	}

  	if (niceval < task_nice(p) && !can_nice(p, niceval)) {

  		error = -EACCES;
  		goto out;
  	}
  	no_nice = security_task_setnice(p, niceval);
  	if (no_nice) {
  		error = no_nice;
  		goto out;
  	}
  	if (error == -ESRCH)
  		error = 0;
  	set_user_nice(p, niceval);
  out:
  	return error;
  }

  SYSCALL_DEFINE3(setpriority, int, which, int, who, int, niceval)

  {
  	struct task_struct *g, *p;
  	struct user_struct *user;

  	const struct cred *cred = current_cred();

  	int error = -EINVAL;

  	struct pid *pgrp;

  	kuid_t uid;

  	if (which > PRIO_USER || which < PRIO_PROCESS)

  		goto out;
  
  	/* normalize: avoid signed division (rounding problems) */
  	error = -ESRCH;

  	if (niceval < MIN_NICE)
  		niceval = MIN_NICE;
  	if (niceval > MAX_NICE)
  		niceval = MAX_NICE;

  	rcu_read_lock();

  	read_lock(&tasklist_lock);
  	switch (which) {

  	case PRIO_PROCESS:
  		if (who)
  			p = find_task_by_vpid(who);
  		else
  			p = current;
  		if (p)
  			error = set_one_prio(p, niceval, error);
  		break;
  	case PRIO_PGRP:
  		if (who)
  			pgrp = find_vpid(who);
  		else
  			pgrp = task_pgrp(current);
  		do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
  			error = set_one_prio(p, niceval, error);
  		} while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
  		break;
  	case PRIO_USER:
  		uid = make_kuid(cred->user_ns, who);
  		user = cred->user;
  		if (!who)
  			uid = cred->uid;
  		else if (!uid_eq(uid, cred->uid)) {
  			user = find_user(uid);
  			if (!user)

  				goto out_unlock;	/* No processes for this user */

  		}
  		do_each_thread(g, p) {

  			if (uid_eq(task_uid(p), uid) && task_pid_vnr(p))

  				error = set_one_prio(p, niceval, error);
  		} while_each_thread(g, p);
  		if (!uid_eq(uid, cred->uid))
  			free_uid(user);		/* For find_user() */
  		break;

  	}
  out_unlock:
  	read_unlock(&tasklist_lock);

  	rcu_read_unlock();

  out:
  	return error;
  }
  
  /*
   * Ugh. To avoid negative return values, "getpriority()" will
   * not return the normal nice-value, but a negated value that
   * has been offset by 20 (ie it returns 40..1 instead of -20..19)
   * to stay compatible.
   */

  SYSCALL_DEFINE2(getpriority, int, which, int, who)

  {
  	struct task_struct *g, *p;
  	struct user_struct *user;

  	const struct cred *cred = current_cred();

  	long niceval, retval = -ESRCH;

  	struct pid *pgrp;

  	kuid_t uid;

  	if (which > PRIO_USER || which < PRIO_PROCESS)

  		return -EINVAL;

  	rcu_read_lock();

  	read_lock(&tasklist_lock);
  	switch (which) {

  	case PRIO_PROCESS:
  		if (who)
  			p = find_task_by_vpid(who);
  		else
  			p = current;
  		if (p) {
  			niceval = nice_to_rlimit(task_nice(p));
  			if (niceval > retval)
  				retval = niceval;
  		}
  		break;
  	case PRIO_PGRP:
  		if (who)
  			pgrp = find_vpid(who);
  		else
  			pgrp = task_pgrp(current);
  		do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
  			niceval = nice_to_rlimit(task_nice(p));
  			if (niceval > retval)
  				retval = niceval;
  		} while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
  		break;
  	case PRIO_USER:
  		uid = make_kuid(cred->user_ns, who);
  		user = cred->user;
  		if (!who)
  			uid = cred->uid;
  		else if (!uid_eq(uid, cred->uid)) {
  			user = find_user(uid);
  			if (!user)
  				goto out_unlock;	/* No processes for this user */
  		}
  		do_each_thread(g, p) {

  			if (uid_eq(task_uid(p), uid) && task_pid_vnr(p)) {

  				niceval = nice_to_rlimit(task_nice(p));

  				if (niceval > retval)
  					retval = niceval;
  			}

  		} while_each_thread(g, p);
  		if (!uid_eq(uid, cred->uid))
  			free_uid(user);		/* for find_user() */
  		break;

  	}
  out_unlock:
  	read_unlock(&tasklist_lock);

  	rcu_read_unlock();

  
  	return retval;
  }

  /*
   * Unprivileged users may change the real gid to the effective gid
   * or vice versa.  (BSD-style)
   *
   * If you set the real gid at all, or set the effective gid to a value not
   * equal to the real gid, then the saved gid is set to the new effective gid.
   *
   * This makes it possible for a setgid program to completely drop its
   * privileges, which is often a useful assertion to make when you are doing
   * a security audit over a program.
   *
   * The general idea is that a program which uses just setregid() will be
   * 100% compatible with BSD.  A program which uses just setgid() will be

   * 100% compatible with POSIX with saved IDs.

   *
   * SMP: There are not races, the GIDs are checked only by filesystem
   *      operations (as far as semantic preservation is concerned).
   */

  #ifdef CONFIG_MULTIUSER

  SYSCALL_DEFINE2(setregid, gid_t, rgid, gid_t, egid)

  {

  	struct user_namespace *ns = current_user_ns();

  	const struct cred *old;
  	struct cred *new;

  	int retval;

  	kgid_t krgid, kegid;
  
  	krgid = make_kgid(ns, rgid);
  	kegid = make_kgid(ns, egid);
  
  	if ((rgid != (gid_t) -1) && !gid_valid(krgid))
  		return -EINVAL;
  	if ((egid != (gid_t) -1) && !gid_valid(kegid))
  		return -EINVAL;

  	new = prepare_creds();
  	if (!new)
  		return -ENOMEM;
  	old = current_cred();

  	retval = -EPERM;

  	if (rgid != (gid_t) -1) {

  		if (gid_eq(old->gid, krgid) ||
  		    gid_eq(old->egid, krgid) ||

  		    ns_capable(old->user_ns, CAP_SETGID))

  			new->gid = krgid;

  		else

  			goto error;

  	}
  	if (egid != (gid_t) -1) {

  		if (gid_eq(old->gid, kegid) ||
  		    gid_eq(old->egid, kegid) ||
  		    gid_eq(old->sgid, kegid) ||

  		    ns_capable(old->user_ns, CAP_SETGID))

  			new->egid = kegid;

  		else

  			goto error;

  	}

  	if (rgid != (gid_t) -1 ||

  	    (egid != (gid_t) -1 && !gid_eq(kegid, old->gid)))

  		new->sgid = new->egid;
  	new->fsgid = new->egid;
  
  	return commit_creds(new);
  
  error:
  	abort_creds(new);
  	return retval;

  }
  
  /*

   * setgid() is implemented like SysV w/ SAVED_IDS

   *
   * SMP: Same implicit races as above.
   */

  SYSCALL_DEFINE1(setgid, gid_t, gid)

  {

  	struct user_namespace *ns = current_user_ns();

  	const struct cred *old;
  	struct cred *new;

  	int retval;

  	kgid_t kgid;
  
  	kgid = make_kgid(ns, gid);
  	if (!gid_valid(kgid))
  		return -EINVAL;

  	new = prepare_creds();
  	if (!new)
  		return -ENOMEM;
  	old = current_cred();

  	retval = -EPERM;

  	if (ns_capable(old->user_ns, CAP_SETGID))

  		new->gid = new->egid = new->sgid = new->fsgid = kgid;
  	else if (gid_eq(kgid, old->gid) || gid_eq(kgid, old->sgid))
  		new->egid = new->fsgid = kgid;

  	else

  		goto error;

  	return commit_creds(new);
  
  error:
  	abort_creds(new);
  	return retval;

  }

  /*
   * change the user struct in a credentials set to match the new UID
   */
  static int set_user(struct cred *new)

  {
  	struct user_struct *new_user;

  	new_user = alloc_uid(new->uid);

  	if (!new_user)
  		return -EAGAIN;

  	/*
  	 * We don't fail in case of NPROC limit excess here because too many
  	 * poorly written programs don't check set*uid() return code, assuming
  	 * it never fails if called by root.  We may still enforce NPROC limit
  	 * for programs doing set*uid()+execve() by harmlessly deferring the
  	 * failure to the execve() stage.
  	 */

  	if (atomic_read(&new_user->processes) >= rlimit(RLIMIT_NPROC) &&

  			new_user != INIT_USER)
  		current->flags |= PF_NPROC_EXCEEDED;
  	else
  		current->flags &= ~PF_NPROC_EXCEEDED;

  	free_uid(new->user);
  	new->user = new_user;

  	return 0;
  }
  
  /*
   * Unprivileged users may change the real uid to the effective uid
   * or vice versa.  (BSD-style)
   *
   * If you set the real uid at all, or set the effective uid to a value not
   * equal to the real uid, then the saved uid is set to the new effective uid.
   *
   * This makes it possible for a setuid program to completely drop its
   * privileges, which is often a useful assertion to make when you are doing
   * a security audit over a program.
   *
   * The general idea is that a program which uses just setreuid() will be
   * 100% compatible with BSD.  A program which uses just setuid() will be

   * 100% compatible with POSIX with saved IDs.

   */

  SYSCALL_DEFINE2(setreuid, uid_t, ruid, uid_t, euid)

  {

  	struct user_namespace *ns = current_user_ns();

  	const struct cred *old;
  	struct cred *new;

  	int retval;

  	kuid_t kruid, keuid;
  
  	kruid = make_kuid(ns, ruid);
  	keuid = make_kuid(ns, euid);
  
  	if ((ruid != (uid_t) -1) && !uid_valid(kruid))
  		return -EINVAL;
  	if ((euid != (uid_t) -1) && !uid_valid(keuid))
  		return -EINVAL;

  	new = prepare_creds();
  	if (!new)
  		return -ENOMEM;
  	old = current_cred();

  	retval = -EPERM;

  	if (ruid != (uid_t) -1) {

  		new->uid = kruid;
  		if (!uid_eq(old->uid, kruid) &&
  		    !uid_eq(old->euid, kruid) &&

  		    !ns_capable(old->user_ns, CAP_SETUID))

  			goto error;

  	}
  
  	if (euid != (uid_t) -1) {

  		new->euid = keuid;
  		if (!uid_eq(old->uid, keuid) &&
  		    !uid_eq(old->euid, keuid) &&
  		    !uid_eq(old->suid, keuid) &&

  		    !ns_capable(old->user_ns, CAP_SETUID))

  			goto error;

  	}

  	if (!uid_eq(new->uid, old->uid)) {

  		retval = set_user(new);
  		if (retval < 0)
  			goto error;
  	}

  	if (ruid != (uid_t) -1 ||

  	    (euid != (uid_t) -1 && !uid_eq(keuid, old->uid)))

  		new->suid = new->euid;
  	new->fsuid = new->euid;

  	retval = security_task_fix_setuid(new, old, LSM_SETID_RE);
  	if (retval < 0)
  		goto error;

  	return commit_creds(new);

  error:
  	abort_creds(new);
  	return retval;
  }

  /*

   * setuid() is implemented like SysV with SAVED_IDS
   *

   * Note that SAVED_ID's is deficient in that a setuid root program

   * like sendmail, for example, cannot set its uid to be a normal

   * user and then switch back, because if you're root, setuid() sets
   * the saved uid too.  If you don't like this, blame the bright people
   * in the POSIX committee and/or USG.  Note that the BSD-style setreuid()
   * will allow a root program to temporarily drop privileges and be able to

   * regain them by swapping the real and effective uid.

   */

  SYSCALL_DEFINE1(setuid, uid_t, uid)

  {

  	struct user_namespace *ns = current_user_ns();

  	const struct cred *old;
  	struct cred *new;

  	int retval;

  	kuid_t kuid;
  
  	kuid = make_kuid(ns, uid);
  	if (!uid_valid(kuid))
  		return -EINVAL;

  	new = prepare_creds();
  	if (!new)
  		return -ENOMEM;
  	old = current_cred();

  	retval = -EPERM;

  	if (ns_capable(old->user_ns, CAP_SETUID)) {

  		new->suid = new->uid = kuid;
  		if (!uid_eq(kuid, old->uid)) {

  			retval = set_user(new);
  			if (retval < 0)
  				goto error;

  		}

  	} else if (!uid_eq(kuid, old->uid) && !uid_eq(kuid, new->suid)) {

  		goto error;

  	}

  	new->fsuid = new->euid = kuid;

  
  	retval = security_task_fix_setuid(new, old, LSM_SETID_ID);
  	if (retval < 0)
  		goto error;

  	return commit_creds(new);

  error:
  	abort_creds(new);
  	return retval;

  }
  
  
  /*
   * This function implements a generic ability to update ruid, euid,
   * and suid.  This allows you to implement the 4.4 compatible seteuid().
   */

  SYSCALL_DEFINE3(setresuid, uid_t, ruid, uid_t, euid, uid_t, suid)

  {

  	struct user_namespace *ns = current_user_ns();

  	const struct cred *old;
  	struct cred *new;

  	int retval;

  	kuid_t kruid, keuid, ksuid;
  
  	kruid = make_kuid(ns, ruid);
  	keuid = make_kuid(ns, euid);
  	ksuid = make_kuid(ns, suid);
  
  	if ((ruid != (uid_t) -1) && !uid_valid(kruid))
  		return -EINVAL;
  
  	if ((euid != (uid_t) -1) && !uid_valid(keuid))
  		return -EINVAL;
  
  	if ((suid != (uid_t) -1) && !uid_valid(ksuid))
  		return -EINVAL;

  	new = prepare_creds();
  	if (!new)
  		return -ENOMEM;

  	old = current_cred();

  	retval = -EPERM;

  	if (!ns_capable(old->user_ns, CAP_SETUID)) {

  		if (ruid != (uid_t) -1        && !uid_eq(kruid, old->uid) &&
  		    !uid_eq(kruid, old->euid) && !uid_eq(kruid, old->suid))

  			goto error;

  		if (euid != (uid_t) -1        && !uid_eq(keuid, old->uid) &&
  		    !uid_eq(keuid, old->euid) && !uid_eq(keuid, old->suid))

  			goto error;

  		if (suid != (uid_t) -1        && !uid_eq(ksuid, old->uid) &&
  		    !uid_eq(ksuid, old->euid) && !uid_eq(ksuid, old->suid))

  			goto error;

  	}

  	if (ruid != (uid_t) -1) {

  		new->uid = kruid;
  		if (!uid_eq(kruid, old->uid)) {

  			retval = set_user(new);
  			if (retval < 0)
  				goto error;
  		}

  	}

  	if (euid != (uid_t) -1)

  		new->euid = keuid;

  	if (suid != (uid_t) -1)

  		new->suid = ksuid;

  	new->fsuid = new->euid;

  	retval = security_task_fix_setuid(new, old, LSM_SETID_RES);
  	if (retval < 0)
  		goto error;

  	return commit_creds(new);

  error:
  	abort_creds(new);
  	return retval;

  }

  SYSCALL_DEFINE3(getresuid, uid_t __user *, ruidp, uid_t __user *, euidp, uid_t __user *, suidp)

  {

  	const struct cred *cred = current_cred();

  	int retval;

  	uid_t ruid, euid, suid;
  
  	ruid = from_kuid_munged(cred->user_ns, cred->uid);
  	euid = from_kuid_munged(cred->user_ns, cred->euid);
  	suid = from_kuid_munged(cred->user_ns, cred->suid);

  	retval = put_user(ruid, ruidp);
  	if (!retval) {
  		retval = put_user(euid, euidp);
  		if (!retval)
  			return put_user(suid, suidp);
  	}

  	return retval;
  }
  
  /*
   * Same as above, but for rgid, egid, sgid.
   */

  SYSCALL_DEFINE3(setresgid, gid_t, rgid, gid_t, egid, gid_t, sgid)

  {

  	struct user_namespace *ns = current_user_ns();

  	const struct cred *old;
  	struct cred *new;

  	int retval;

  	kgid_t krgid, kegid, ksgid;
  
  	krgid = make_kgid(ns, rgid);
  	kegid = make_kgid(ns, egid);
  	ksgid = make_kgid(ns, sgid);
  
  	if ((rgid != (gid_t) -1) && !gid_valid(krgid))
  		return -EINVAL;
  	if ((egid != (gid_t) -1) && !gid_valid(kegid))
  		return -EINVAL;
  	if ((sgid != (gid_t) -1) && !gid_valid(ksgid))
  		return -EINVAL;

  	new = prepare_creds();
  	if (!new)
  		return -ENOMEM;
  	old = current_cred();

  	retval = -EPERM;

  	if (!ns_capable(old->user_ns, CAP_SETGID)) {

  		if (rgid != (gid_t) -1        && !gid_eq(krgid, old->gid) &&
  		    !gid_eq(krgid, old->egid) && !gid_eq(krgid, old->sgid))

  			goto error;

  		if (egid != (gid_t) -1        && !gid_eq(kegid, old->gid) &&
  		    !gid_eq(kegid, old->egid) && !gid_eq(kegid, old->sgid))

  			goto error;

  		if (sgid != (gid_t) -1        && !gid_eq(ksgid, old->gid) &&
  		    !gid_eq(ksgid, old->egid) && !gid_eq(ksgid, old->sgid))

  			goto error;

  	}

  	if (rgid != (gid_t) -1)

  		new->gid = krgid;

  	if (egid != (gid_t) -1)

  		new->egid = kegid;

  	if (sgid != (gid_t) -1)

  		new->sgid = ksgid;

  	new->fsgid = new->egid;

  	return commit_creds(new);
  
  error:
  	abort_creds(new);
  	return retval;

  }

  SYSCALL_DEFINE3(getresgid, gid_t __user *, rgidp, gid_t __user *, egidp, gid_t __user *, sgidp)

  {

  	const struct cred *cred = current_cred();

  	int retval;

  	gid_t rgid, egid, sgid;
  
  	rgid = from_kgid_munged(cred->user_ns, cred->gid);
  	egid = from_kgid_munged(cred->user_ns, cred->egid);
  	sgid = from_kgid_munged(cred->user_ns, cred->sgid);

  	retval = put_user(rgid, rgidp);
  	if (!retval) {
  		retval = put_user(egid, egidp);
  		if (!retval)
  			retval = put_user(sgid, sgidp);
  	}

  
  	return retval;
  }
  
  
  /*
   * "setfsuid()" sets the fsuid - the uid used for filesystem checks. This
   * is used for "access()" and for the NFS daemon (letting nfsd stay at
   * whatever uid it wants to). It normally shadows "euid", except when
   * explicitly set by setfsuid() or for access..
   */

  SYSCALL_DEFINE1(setfsuid, uid_t, uid)

  {

  	const struct cred *old;
  	struct cred *new;
  	uid_t old_fsuid;

  	kuid_t kuid;
  
  	old = current_cred();
  	old_fsuid = from_kuid_munged(old->user_ns, old->fsuid);
  
  	kuid = make_kuid(old->user_ns, uid);
  	if (!uid_valid(kuid))
  		return old_fsuid;

  	new = prepare_creds();
  	if (!new)

  		return old_fsuid;

  	if (uid_eq(kuid, old->uid)  || uid_eq(kuid, old->euid)  ||
  	    uid_eq(kuid, old->suid) || uid_eq(kuid, old->fsuid) ||

  	    ns_capable(old->user_ns, CAP_SETUID)) {

  		if (!uid_eq(kuid, old->fsuid)) {
  			new->fsuid = kuid;

  			if (security_task_fix_setuid(new, old, LSM_SETID_FS) == 0)
  				goto change_okay;

  		}

  	}

  	abort_creds(new);
  	return old_fsuid;

  change_okay:
  	commit_creds(new);

  	return old_fsuid;
  }
  
  /*

   * Samma på svenska..

   */

  SYSCALL_DEFINE1(setfsgid, gid_t, gid)

  {

  	const struct cred *old;
  	struct cred *new;
  	gid_t old_fsgid;

  	kgid_t kgid;
  
  	old = current_cred();
  	old_fsgid = from_kgid_munged(old->user_ns, old->fsgid);
  
  	kgid = make_kgid(old->user_ns, gid);
  	if (!gid_valid(kgid))
  		return old_fsgid;

  
  	new = prepare_creds();
  	if (!new)

  		return old_fsgid;

  	if (gid_eq(kgid, old->gid)  || gid_eq(kgid, old->egid)  ||
  	    gid_eq(kgid, old->sgid) || gid_eq(kgid, old->fsgid) ||

  	    ns_capable(old->user_ns, CAP_SETGID)) {

  		if (!gid_eq(kgid, old->fsgid)) {
  			new->fsgid = kgid;

  			goto change_okay;

  		}

  	}

  	abort_creds(new);
  	return old_fsgid;
  
  change_okay:
  	commit_creds(new);

  	return old_fsgid;
  }

  #endif /* CONFIG_MULTIUSER */

  /**
   * sys_getpid - return the thread group id of the current process
   *
   * Note, despite the name, this returns the tgid not the pid.  The tgid and
   * the pid are identical unless CLONE_THREAD was specified on clone() in
   * which case the tgid is the same in all threads of the same group.
   *
   * This is SMP safe as current->tgid does not change.
   */
  SYSCALL_DEFINE0(getpid)
  {
  	return task_tgid_vnr(current);
  }
  
  /* Thread ID - the internal kernel "pid" */
  SYSCALL_DEFINE0(gettid)
  {
  	return task_pid_vnr(current);
  }
  
  /*
   * Accessing ->real_parent is not SMP-safe, it could
   * change from under us. However, we can use a stale
   * value of ->real_parent under rcu_read_lock(), see
   * release_task()->call_rcu(delayed_put_task_struct).
   */
  SYSCALL_DEFINE0(getppid)
  {
  	int pid;
  
  	rcu_read_lock();
  	pid = task_tgid_vnr(rcu_dereference(current->real_parent));
  	rcu_read_unlock();
  
  	return pid;
  }
  
  SYSCALL_DEFINE0(getuid)
  {
  	/* Only we change this so SMP safe */
  	return from_kuid_munged(current_user_ns(), current_uid());
  }
  
  SYSCALL_DEFINE0(geteuid)
  {
  	/* Only we change this so SMP safe */
  	return from_kuid_munged(current_user_ns(), current_euid());
  }
  
  SYSCALL_DEFINE0(getgid)
  {
  	/* Only we change this so SMP safe */
  	return from_kgid_munged(current_user_ns(), current_gid());
  }
  
  SYSCALL_DEFINE0(getegid)
  {
  	/* Only we change this so SMP safe */
  	return from_kgid_munged(current_user_ns(), current_egid());
  }

  static void do_sys_times(struct tms *tms)

  {

  	u64 tgutime, tgstime, cutime, cstime;

  	thread_group_cputime_adjusted(current, &tgutime, &tgstime);

  	cutime = current->signal->cutime;
  	cstime = current->signal->cstime;

  	tms->tms_utime = nsec_to_clock_t(tgutime);
  	tms->tms_stime = nsec_to_clock_t(tgstime);
  	tms->tms_cutime = nsec_to_clock_t(cutime);
  	tms->tms_cstime = nsec_to_clock_t(cstime);

  }

  SYSCALL_DEFINE1(times, struct tms __user *, tbuf)

  {

  	if (tbuf) {
  		struct tms tmp;

  
  		do_sys_times(&tmp);

  		if (copy_to_user(tbuf, &tmp, sizeof(struct tms)))
  			return -EFAULT;
  	}

  	force_successful_syscall_return();

  	return (long) jiffies_64_to_clock_t(get_jiffies_64());
  }

  #ifdef CONFIG_COMPAT
  static compat_clock_t clock_t_to_compat_clock_t(clock_t x)
  {
  	return compat_jiffies_to_clock_t(clock_t_to_jiffies(x));
  }
  
  COMPAT_SYSCALL_DEFINE1(times, struct compat_tms __user *, tbuf)
  {
  	if (tbuf) {
  		struct tms tms;
  		struct compat_tms tmp;
  
  		do_sys_times(&tms);
  		/* Convert our struct tms to the compat version. */
  		tmp.tms_utime = clock_t_to_compat_clock_t(tms.tms_utime);
  		tmp.tms_stime = clock_t_to_compat_clock_t(tms.tms_stime);
  		tmp.tms_cutime = clock_t_to_compat_clock_t(tms.tms_cutime);
  		tmp.tms_cstime = clock_t_to_compat_clock_t(tms.tms_cstime);
  		if (copy_to_user(tbuf, &tmp, sizeof(tmp)))
  			return -EFAULT;
  	}
  	force_successful_syscall_return();
  	return compat_jiffies_to_clock_t(jiffies);
  }
  #endif

  /*
   * This needs some heavy checking ...
   * I just haven't the stomach for it. I also don't fully
   * understand sessions/pgrp etc. Let somebody who does explain it.
   *
   * OK, I think I have the protection semantics right.... this is really
   * only important on a multi-user system anyway, to make sure one user
   * can't send a signal to a process owned by another.  -TYT, 12/12/91
   *

   * !PF_FORKNOEXEC check to conform completely to POSIX.

   */

  SYSCALL_DEFINE2(setpgid, pid_t, pid, pid_t, pgid)

  {
  	struct task_struct *p;

  	struct task_struct *group_leader = current->group_leader;

  	struct pid *pgrp;
  	int err;

  
  	if (!pid)

  		pid = task_pid_vnr(group_leader);

  	if (!pgid)
  		pgid = pid;
  	if (pgid < 0)
  		return -EINVAL;

  	rcu_read_lock();

  
  	/* From this point forward we keep holding onto the tasklist lock
  	 * so that our parent does not change from under us. -DaveM
  	 */
  	write_lock_irq(&tasklist_lock);
  
  	err = -ESRCH;

  	p = find_task_by_vpid(pid);

  	if (!p)
  		goto out;
  
  	err = -EINVAL;
  	if (!thread_group_leader(p))
  		goto out;

  	if (same_thread_group(p->real_parent, group_leader)) {

  		err = -EPERM;

  		if (task_session(p) != task_session(group_leader))

  			goto out;
  		err = -EACCES;

  		if (!(p->flags & PF_FORKNOEXEC))

  			goto out;
  	} else {
  		err = -ESRCH;

  		if (p != group_leader)

  			goto out;
  	}
  
  	err = -EPERM;
  	if (p->signal->leader)
  		goto out;

  	pgrp = task_pid(p);

  	if (pgid != pid) {

  		struct task_struct *g;

  		pgrp = find_vpid(pgid);
  		g = pid_task(pgrp, PIDTYPE_PGID);

  		if (!g || task_session(g) != task_session(group_leader))

  			goto out;

  	}

  	err = security_task_setpgid(p, pgid);
  	if (err)
  		goto out;

  	if (task_pgrp(p) != pgrp)

  		change_pid(p, PIDTYPE_PGID, pgrp);

  
  	err = 0;
  out:
  	/* All paths lead to here, thus we are safe. -DaveM */
  	write_unlock_irq(&tasklist_lock);

  	rcu_read_unlock();

  	return err;
  }

  SYSCALL_DEFINE1(getpgid, pid_t, pid)

  {

  	struct task_struct *p;
  	struct pid *grp;
  	int retval;
  
  	rcu_read_lock();

  	if (!pid)

  		grp = task_pgrp(current);

  	else {

  		retval = -ESRCH;

  		p = find_task_by_vpid(pid);
  		if (!p)
  			goto out;
  		grp = task_pgrp(p);
  		if (!grp)
  			goto out;
  
  		retval = security_task_getpgid(p);
  		if (retval)
  			goto out;

  	}

  	retval = pid_vnr(grp);
  out:
  	rcu_read_unlock();
  	return retval;

  }
  
  #ifdef __ARCH_WANT_SYS_GETPGRP

  SYSCALL_DEFINE0(getpgrp)

  {

  	return sys_getpgid(0);

  }
  
  #endif

  SYSCALL_DEFINE1(getsid, pid_t, pid)

  {

  	struct task_struct *p;
  	struct pid *sid;
  	int retval;
  
  	rcu_read_lock();

  	if (!pid)

  		sid = task_session(current);

  	else {

  		retval = -ESRCH;

  		p = find_task_by_vpid(pid);
  		if (!p)
  			goto out;
  		sid = task_session(p);
  		if (!sid)
  			goto out;
  
  		retval = security_task_getsid(p);
  		if (retval)
  			goto out;

  	}

  	retval = pid_vnr(sid);
  out:
  	rcu_read_unlock();
  	return retval;

  }

  static void set_special_pids(struct pid *pid)
  {
  	struct task_struct *curr = current->group_leader;
  
  	if (task_session(curr) != pid)
  		change_pid(curr, PIDTYPE_SID, pid);
  
  	if (task_pgrp(curr) != pid)
  		change_pid(curr, PIDTYPE_PGID, pid);
  }

  SYSCALL_DEFINE0(setsid)

  {

  	struct task_struct *group_leader = current->group_leader;

  	struct pid *sid = task_pid(group_leader);
  	pid_t session = pid_vnr(sid);

  	int err = -EPERM;

  	write_lock_irq(&tasklist_lock);

  	/* Fail if I am already a session leader */
  	if (group_leader->signal->leader)
  		goto out;

  	/* Fail if a process group id already exists that equals the
  	 * proposed session id.

  	 */

  	if (pid_task(sid, PIDTYPE_PGID))

  		goto out;

  	group_leader->signal->leader = 1;

  	set_special_pids(sid);

  	proc_clear_tty(group_leader);

  	err = session;

  out:
  	write_unlock_irq(&tasklist_lock);

  	if (err > 0) {

  		proc_sid_connector(group_leader);

  		sched_autogroup_create_attach(group_leader);
  	}

  	return err;
  }

  DECLARE_RWSEM(uts_sem);

  #ifdef COMPAT_UTS_MACHINE
  #define override_architecture(name) \

  	(personality(current->personality) == PER_LINUX32 && \

  	 copy_to_user(name->machine, COMPAT_UTS_MACHINE, \
  		      sizeof(COMPAT_UTS_MACHINE)))
  #else
  #define override_architecture(name)	0
  #endif

  /*
   * Work around broken programs that cannot handle "Linux 3.0".
   * Instead we map 3.x to 2.6.40+x, so e.g. 3.0 would be 2.6.40

   * And we map 4.x to 2.6.60+x, so 4.0 would be 2.6.60.

   */

  static int override_release(char __user *release, size_t len)

  {
  	int ret = 0;

  
  	if (current->personality & UNAME26) {

  		const char *rest = UTS_RELEASE;
  		char buf[65] = { 0 };

  		int ndots = 0;
  		unsigned v;

  		size_t copy;

  
  		while (*rest) {
  			if (*rest == '.' && ++ndots >= 3)
  				break;
  			if (!isdigit(*rest) && *rest != '.')
  				break;
  			rest++;
  		}

  		v = ((LINUX_VERSION_CODE >> 8) & 0xff) + 60;

  		copy = clamp_t(size_t, len, 1, sizeof(buf));

  		copy = scnprintf(buf, copy, "2.6.%u%s", v, rest);
  		ret = copy_to_user(release, buf, copy + 1);

  	}
  	return ret;
  }

  SYSCALL_DEFINE1(newuname, struct new_utsname __user *, name)

  {

  	struct new_utsname tmp;

  
  	down_read(&uts_sem);

  	memcpy(&tmp, utsname(), sizeof(tmp));

  	up_read(&uts_sem);

  	if (copy_to_user(name, &tmp, sizeof(tmp)))
  		return -EFAULT;

  	if (override_release(name->release, sizeof(name->release)))
  		return -EFAULT;
  	if (override_architecture(name))
  		return -EFAULT;
  	return 0;

  }

  #ifdef __ARCH_WANT_SYS_OLD_UNAME
  /*
   * Old cruft
   */
  SYSCALL_DEFINE1(uname, struct old_utsname __user *, name)
  {

  	struct old_utsname tmp;

  
  	if (!name)
  		return -EFAULT;
  
  	down_read(&uts_sem);

  	memcpy(&tmp, utsname(), sizeof(tmp));

  	up_read(&uts_sem);

  	if (copy_to_user(name, &tmp, sizeof(tmp)))
  		return -EFAULT;

  	if (override_release(name->release, sizeof(name->release)))
  		return -EFAULT;
  	if (override_architecture(name))
  		return -EFAULT;
  	return 0;

  }
  
  SYSCALL_DEFINE1(olduname, struct oldold_utsname __user *, name)
  {

  	struct oldold_utsname tmp = {};

  
  	if (!name)
  		return -EFAULT;

  
  	down_read(&uts_sem);

  	memcpy(&tmp.sysname, &utsname()->sysname, __OLD_UTS_LEN);
  	memcpy(&tmp.nodename, &utsname()->nodename, __OLD_UTS_LEN);
  	memcpy(&tmp.release, &utsname()->release, __OLD_UTS_LEN);
  	memcpy(&tmp.version, &utsname()->version, __OLD_UTS_LEN);
  	memcpy(&tmp.machine, &utsname()->machine, __OLD_UTS_LEN);

  	up_read(&uts_sem);

  	if (copy_to_user(name, &tmp, sizeof(tmp)))
  		return -EFAULT;

  	if (override_architecture(name))
  		return -EFAULT;
  	if (override_release(name->release, sizeof(name->release)))
  		return -EFAULT;
  	return 0;

  }
  #endif

  SYSCALL_DEFINE2(sethostname, char __user *, name, int, len)

  {
  	int errno;
  	char tmp[__NEW_UTS_LEN];

  	if (!ns_capable(current->nsproxy->uts_ns->user_ns, CAP_SYS_ADMIN))

  		return -EPERM;

  	if (len < 0 || len > __NEW_UTS_LEN)
  		return -EINVAL;

  	errno = -EFAULT;
  	if (!copy_from_user(tmp, name, len)) {

  		struct new_utsname *u;

  		down_write(&uts_sem);
  		u = utsname();

  		memcpy(u->nodename, tmp, len);
  		memset(u->nodename + len, 0, sizeof(u->nodename) - len);

  		errno = 0;

  		uts_proc_notify(UTS_PROC_HOSTNAME);

  		up_write(&uts_sem);

  	}

  	return errno;
  }
  
  #ifdef __ARCH_WANT_SYS_GETHOSTNAME

  SYSCALL_DEFINE2(gethostname, char __user *, name, int, len)

  {

  	int i;

  	struct new_utsname *u;

  	char tmp[__NEW_UTS_LEN + 1];

  
  	if (len < 0)
  		return -EINVAL;
  	down_read(&uts_sem);

  	u = utsname();
  	i = 1 + strlen(u->nodename);

  	if (i > len)
  		i = len;

  	memcpy(tmp, u->nodename, i);

  	up_read(&uts_sem);

  	if (copy_to_user(name, tmp, i))
  		return -EFAULT;
  	return 0;

  }
  
  #endif
  
  /*
   * Only setdomainname; getdomainname can be implemented by calling
   * uname()
   */

  SYSCALL_DEFINE2(setdomainname, char __user *, name, int, len)

  {
  	int errno;
  	char tmp[__NEW_UTS_LEN];

  	if (!ns_capable(current->nsproxy->uts_ns->user_ns, CAP_SYS_ADMIN))

  		return -EPERM;
  	if (len < 0 || len > __NEW_UTS_LEN)
  		return -EINVAL;

  	errno = -EFAULT;
  	if (!copy_from_user(tmp, name, len)) {

  		struct new_utsname *u;

  		down_write(&uts_sem);
  		u = utsname();

  		memcpy(u->domainname, tmp, len);
  		memset(u->domainname + len, 0, sizeof(u->domainname) - len);

  		errno = 0;

  		uts_proc_notify(UTS_PROC_DOMAINNAME);

  		up_write(&uts_sem);

  	}

  	return errno;
  }

  SYSCALL_DEFINE2(getrlimit, unsigned int, resource, struct rlimit __user *, rlim)

  {

  	struct rlimit value;
  	int ret;
  
  	ret = do_prlimit(current, resource, NULL, &value);
  	if (!ret)
  		ret = copy_to_user(rlim, &value, sizeof(*rlim)) ? -EFAULT : 0;
  
  	return ret;

  }

  #ifdef CONFIG_COMPAT
  
  COMPAT_SYSCALL_DEFINE2(setrlimit, unsigned int, resource,
  		       struct compat_rlimit __user *, rlim)
  {
  	struct rlimit r;
  	struct compat_rlimit r32;
  
  	if (copy_from_user(&r32, rlim, sizeof(struct compat_rlimit)))
  		return -EFAULT;
  
  	if (r32.rlim_cur == COMPAT_RLIM_INFINITY)
  		r.rlim_cur = RLIM_INFINITY;
  	else
  		r.rlim_cur = r32.rlim_cur;
  	if (r32.rlim_max == COMPAT_RLIM_INFINITY)
  		r.rlim_max = RLIM_INFINITY;
  	else
  		r.rlim_max = r32.rlim_max;
  	return do_prlimit(current, resource, &r, NULL);
  }
  
  COMPAT_SYSCALL_DEFINE2(getrlimit, unsigned int, resource,
  		       struct compat_rlimit __user *, rlim)
  {
  	struct rlimit r;
  	int ret;
  
  	ret = do_prlimit(current, resource, NULL, &r);
  	if (!ret) {

  		struct compat_rlimit r32;

  		if (r.rlim_cur > COMPAT_RLIM_INFINITY)
  			r32.rlim_cur = COMPAT_RLIM_INFINITY;
  		else
  			r32.rlim_cur = r.rlim_cur;
  		if (r.rlim_max > COMPAT_RLIM_INFINITY)
  			r32.rlim_max = COMPAT_RLIM_INFINITY;
  		else
  			r32.rlim_max = r.rlim_max;
  
  		if (copy_to_user(rlim, &r32, sizeof(struct compat_rlimit)))
  			return -EFAULT;
  	}
  	return ret;
  }
  
  #endif

  #ifdef __ARCH_WANT_SYS_OLD_GETRLIMIT
  
  /*
   *	Back compatibility for getrlimit. Needed for some apps.
   */

  SYSCALL_DEFINE2(old_getrlimit, unsigned int, resource,
  		struct rlimit __user *, rlim)

  {
  	struct rlimit x;
  	if (resource >= RLIM_NLIMITS)
  		return -EINVAL;

  	resource = array_index_nospec(resource, RLIM_NLIMITS);

  	task_lock(current->group_leader);
  	x = current->signal->rlim[resource];
  	task_unlock(current->group_leader);

  	if (x.rlim_cur > 0x7FFFFFFF)

  		x.rlim_cur = 0x7FFFFFFF;

  	if (x.rlim_max > 0x7FFFFFFF)

  		x.rlim_max = 0x7FFFFFFF;

  	return copy_to_user(rlim, &x, sizeof(x)) ? -EFAULT : 0;

  }

  #ifdef CONFIG_COMPAT
  COMPAT_SYSCALL_DEFINE2(old_getrlimit, unsigned int, resource,
  		       struct compat_rlimit __user *, rlim)
  {
  	struct rlimit r;
  
  	if (resource >= RLIM_NLIMITS)
  		return -EINVAL;

  	resource = array_index_nospec(resource, RLIM_NLIMITS);

  	task_lock(current->group_leader);
  	r = current->signal->rlim[resource];
  	task_unlock(current->group_leader);
  	if (r.rlim_cur > 0x7FFFFFFF)
  		r.rlim_cur = 0x7FFFFFFF;
  	if (r.rlim_max > 0x7FFFFFFF)
  		r.rlim_max = 0x7FFFFFFF;
  
  	if (put_user(r.rlim_cur, &rlim->rlim_cur) ||
  	    put_user(r.rlim_max, &rlim->rlim_max))
  		return -EFAULT;
  	return 0;
  }
  #endif

  #endif

  static inline bool rlim64_is_infinity(__u64 rlim64)
  {
  #if BITS_PER_LONG < 64
  	return rlim64 >= ULONG_MAX;
  #else
  	return rlim64 == RLIM64_INFINITY;
  #endif
  }
  
  static void rlim_to_rlim64(const struct rlimit *rlim, struct rlimit64 *rlim64)
  {
  	if (rlim->rlim_cur == RLIM_INFINITY)
  		rlim64->rlim_cur = RLIM64_INFINITY;
  	else
  		rlim64->rlim_cur = rlim->rlim_cur;
  	if (rlim->rlim_max == RLIM_INFINITY)
  		rlim64->rlim_max = RLIM64_INFINITY;
  	else
  		rlim64->rlim_max = rlim->rlim_max;
  }
  
  static void rlim64_to_rlim(const struct rlimit64 *rlim64, struct rlimit *rlim)
  {
  	if (rlim64_is_infinity(rlim64->rlim_cur))
  		rlim->rlim_cur = RLIM_INFINITY;
  	else
  		rlim->rlim_cur = (unsigned long)rlim64->rlim_cur;
  	if (rlim64_is_infinity(rlim64->rlim_max))
  		rlim->rlim_max = RLIM_INFINITY;
  	else
  		rlim->rlim_max = (unsigned long)rlim64->rlim_max;
  }

  /* make sure you are allowed to change @tsk limits before calling this */

  int do_prlimit(struct task_struct *tsk, unsigned int resource,
  		struct rlimit *new_rlim, struct rlimit *old_rlim)

  {

  	struct rlimit *rlim;

  	int retval = 0;

  
  	if (resource >= RLIM_NLIMITS)
  		return -EINVAL;

  	if (new_rlim) {
  		if (new_rlim->rlim_cur > new_rlim->rlim_max)
  			return -EINVAL;
  		if (resource == RLIMIT_NOFILE &&
  				new_rlim->rlim_max > sysctl_nr_open)
  			return -EPERM;
  	}

  	/* protect tsk->signal and tsk->sighand from disappearing */
  	read_lock(&tasklist_lock);
  	if (!tsk->sighand) {
  		retval = -ESRCH;
  		goto out;
  	}

  	rlim = tsk->signal->rlim + resource;

  	task_lock(tsk->group_leader);

  	if (new_rlim) {

  		/* Keep the capable check against init_user_ns until
  		   cgroups can contain all limits */

  		if (new_rlim->rlim_max > rlim->rlim_max &&
  				!capable(CAP_SYS_RESOURCE))
  			retval = -EPERM;
  		if (!retval)

  			retval = security_task_setrlimit(tsk, resource, new_rlim);

  		if (resource == RLIMIT_CPU && new_rlim->rlim_cur == 0) {
  			/*
  			 * The caller is asking for an immediate RLIMIT_CPU
  			 * expiry.  But we use the zero value to mean "it was
  			 * never set".  So let's cheat and make it one second
  			 * instead
  			 */
  			new_rlim->rlim_cur = 1;
  		}
  	}
  	if (!retval) {
  		if (old_rlim)
  			*old_rlim = *rlim;
  		if (new_rlim)
  			*rlim = *new_rlim;

  	}

  	task_unlock(tsk->group_leader);

  	/*
  	 * RLIMIT_CPU handling.   Note that the kernel fails to return an error
  	 * code if it rejected the user's attempt to set RLIMIT_CPU.  This is a
  	 * very long-standing error, and fixing it now risks breakage of
  	 * applications, so we live with it
  	 */

  	 if (!retval && new_rlim && resource == RLIMIT_CPU &&

  	     new_rlim->rlim_cur != RLIM_INFINITY &&
  	     IS_ENABLED(CONFIG_POSIX_TIMERS))

  		update_rlimit_cpu(tsk, new_rlim->rlim_cur);

  out:

  	read_unlock(&tasklist_lock);

  	return retval;

  }

  /* rcu lock must be held */

  static int check_prlimit_permission(struct task_struct *task,
  				    unsigned int flags)

  {
  	const struct cred *cred = current_cred(), *tcred;

  	bool id_match;

  	if (current == task)
  		return 0;

  	tcred = __task_cred(task);

  	id_match = (uid_eq(cred->uid, tcred->euid) &&
  		    uid_eq(cred->uid, tcred->suid) &&
  		    uid_eq(cred->uid, tcred->uid)  &&
  		    gid_eq(cred->gid, tcred->egid) &&
  		    gid_eq(cred->gid, tcred->sgid) &&
  		    gid_eq(cred->gid, tcred->gid));
  	if (!id_match && !ns_capable(tcred->user_ns, CAP_SYS_RESOURCE))
  		return -EPERM;

  	return security_task_prlimit(cred, tcred, flags);

  }
  
  SYSCALL_DEFINE4(prlimit64, pid_t, pid, unsigned int, resource,
  		const struct rlimit64 __user *, new_rlim,
  		struct rlimit64 __user *, old_rlim)
  {
  	struct rlimit64 old64, new64;
  	struct rlimit old, new;
  	struct task_struct *tsk;

  	unsigned int checkflags = 0;

  	int ret;

  	if (old_rlim)
  		checkflags |= LSM_PRLIMIT_READ;

  	if (new_rlim) {
  		if (copy_from_user(&new64, new_rlim, sizeof(new64)))
  			return -EFAULT;
  		rlim64_to_rlim(&new64, &new);

  		checkflags |= LSM_PRLIMIT_WRITE;

  	}
  
  	rcu_read_lock();
  	tsk = pid ? find_task_by_vpid(pid) : current;
  	if (!tsk) {
  		rcu_read_unlock();
  		return -ESRCH;
  	}

  	ret = check_prlimit_permission(tsk, checkflags);

  	if (ret) {
  		rcu_read_unlock();
  		return ret;
  	}
  	get_task_struct(tsk);
  	rcu_read_unlock();
  
  	ret = do_prlimit(tsk, resource, new_rlim ? &new : NULL,
  			old_rlim ? &old : NULL);
  
  	if (!ret && old_rlim) {
  		rlim_to_rlim64(&old, &old64);
  		if (copy_to_user(old_rlim, &old64, sizeof(old64)))
  			ret = -EFAULT;
  	}
  
  	put_task_struct(tsk);
  	return ret;
  }

  SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim)
  {
  	struct rlimit new_rlim;
  
  	if (copy_from_user(&new_rlim, rlim, sizeof(*rlim)))
  		return -EFAULT;

  	return do_prlimit(current, resource, &new_rlim, NULL);

  }

  /*
   * It would make sense to put struct rusage in the task_struct,
   * except that would make the task_struct be *really big*.  After
   * task_struct gets moved into malloc'ed memory, it would
   * make sense to do this.  It will make moving the rest of the information
   * a lot simpler!  (Which we're not doing right now because we're not
   * measuring them yet).
   *

   * When sampling multiple threads for RUSAGE_SELF, under SMP we might have
   * races with threads incrementing their own counters.  But since word
   * reads are atomic, we either get new values or old values and we don't
   * care which for the sums.  We always take the siglock to protect reading
   * the c* fields from p->signal from races with exit.c updating those
   * fields when reaping, so a sample either gets all the additions of a
   * given child after it's reaped, or none so this sample is before reaping.

   *

   * Locking:
   * We need to take the siglock for CHILDEREN, SELF and BOTH
   * for  the cases current multithreaded, non-current single threaded
   * non-current multithreaded.  Thread traversal is now safe with
   * the siglock held.
   * Strictly speaking, we donot need to take the siglock if we are current and
   * single threaded,  as no one else can take our signal_struct away, no one
   * else can  reap the  children to update signal->c* counters, and no one else
   * can race with the signal-> fields. If we do not take any lock, the
   * signal-> fields could be read out of order while another thread was just
   * exiting. So we should  place a read memory barrier when we avoid the lock.
   * On the writer side,  write memory barrier is implied in  __exit_signal
   * as __exit_signal releases  the siglock spinlock after updating the signal->
   * fields. But we don't do this yet to keep things simple.

   *

   */

  static void accumulate_thread_rusage(struct task_struct *t, struct rusage *r)

  {

  	r->ru_nvcsw += t->nvcsw;
  	r->ru_nivcsw += t->nivcsw;
  	r->ru_minflt += t->min_flt;
  	r->ru_majflt += t->maj_flt;
  	r->ru_inblock += task_io_get_inblock(t);
  	r->ru_oublock += task_io_get_oublock(t);
  }

  void getrusage(struct task_struct *p, int who, struct rusage *r)

  {
  	struct task_struct *t;
  	unsigned long flags;

  	u64 tgutime, tgstime, utime, stime;

  	unsigned long maxrss = 0;

  	memset((char *)r, 0, sizeof (*r));

  	utime = stime = 0;

  	if (who == RUSAGE_THREAD) {

  		task_cputime_adjusted(current, &utime, &stime);

  		accumulate_thread_rusage(p, r);

  		maxrss = p->signal->maxrss;

  		goto out;
  	}

  	if (!lock_task_sighand(p, &flags))

  		return;

  	switch (who) {

  	case RUSAGE_BOTH:
  	case RUSAGE_CHILDREN:
  		utime = p->signal->cutime;
  		stime = p->signal->cstime;
  		r->ru_nvcsw = p->signal->cnvcsw;
  		r->ru_nivcsw = p->signal->cnivcsw;
  		r->ru_minflt = p->signal->cmin_flt;
  		r->ru_majflt = p->signal->cmaj_flt;
  		r->ru_inblock = p->signal->cinblock;
  		r->ru_oublock = p->signal->coublock;
  		maxrss = p->signal->cmaxrss;
  
  		if (who == RUSAGE_CHILDREN)

  			break;

  	case RUSAGE_SELF:
  		thread_group_cputime_adjusted(p, &tgutime, &tgstime);
  		utime += tgutime;
  		stime += tgstime;
  		r->ru_nvcsw += p->signal->nvcsw;
  		r->ru_nivcsw += p->signal->nivcsw;
  		r->ru_minflt += p->signal->min_flt;
  		r->ru_majflt += p->signal->maj_flt;
  		r->ru_inblock += p->signal->inblock;
  		r->ru_oublock += p->signal->oublock;
  		if (maxrss < p->signal->maxrss)
  			maxrss = p->signal->maxrss;
  		t = p;
  		do {
  			accumulate_thread_rusage(t, r);
  		} while_each_thread(p, t);
  		break;
  
  	default:
  		BUG();

  	}

  	unlock_task_sighand(p, &flags);

  out:

  	r->ru_utime = ns_to_timeval(utime);
  	r->ru_stime = ns_to_timeval(stime);