// SPDX-License-Identifier: GPL-2.0

  #include <linux/slab.h>
  #include <linux/file.h>
  #include <linux/fdtable.h>

  #include <linux/freezer.h>

  #include <linux/mm.h>
  #include <linux/stat.h>
  #include <linux/fcntl.h>
  #include <linux/swap.h>

  #include <linux/ctype.h>

  #include <linux/string.h>
  #include <linux/init.h>
  #include <linux/pagemap.h>
  #include <linux/perf_event.h>
  #include <linux/highmem.h>
  #include <linux/spinlock.h>
  #include <linux/key.h>
  #include <linux/personality.h>
  #include <linux/binfmts.h>

  #include <linux/coredump.h>

  #include <linux/sched/coredump.h>

  #include <linux/sched/signal.h>

  #include <linux/sched/task_stack.h>

  #include <linux/utsname.h>
  #include <linux/pid_namespace.h>
  #include <linux/module.h>
  #include <linux/namei.h>
  #include <linux/mount.h>
  #include <linux/security.h>
  #include <linux/syscalls.h>
  #include <linux/tsacct_kern.h>
  #include <linux/cn_proc.h>
  #include <linux/audit.h>
  #include <linux/tracehook.h>
  #include <linux/kmod.h>
  #include <linux/fsnotify.h>
  #include <linux/fs_struct.h>
  #include <linux/pipe_fs_i.h>
  #include <linux/oom.h>
  #include <linux/compat.h>

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

  #include <linux/timekeeping.h>

  #include <linux/uaccess.h>

  #include <asm/mmu_context.h>
  #include <asm/tlb.h>
  #include <asm/exec.h>
  
  #include <trace/events/task.h>
  #include "internal.h"
  
  #include <trace/events/sched.h>
  
  int core_uses_pid;

  unsigned int core_pipe_limit;

  char core_pattern[CORENAME_MAX_SIZE] = "core";
  static int core_name_size = CORENAME_MAX_SIZE;

  
  struct core_name {
  	char *corename;
  	int used, size;
  };

  
  /* The maximal length of core_pattern is also specified in sysctl.c */

  static int expand_corename(struct core_name *cn, int size)

  {

  	char *corename = krealloc(cn->corename, size, GFP_KERNEL);

  	if (!corename)

  		return -ENOMEM;

  	if (size > core_name_size) /* racy but harmless */
  		core_name_size = size;
  
  	cn->size = ksize(corename);

  	cn->corename = corename;

  	return 0;
  }

  static __printf(2, 0) int cn_vprintf(struct core_name *cn, const char *fmt,
  				     va_list arg)

  {

  	int free, need;

  	va_list arg_copy;

  again:
  	free = cn->size - cn->used;

  
  	va_copy(arg_copy, arg);
  	need = vsnprintf(cn->corename + cn->used, free, fmt, arg_copy);
  	va_end(arg_copy);

  	if (need < free) {
  		cn->used += need;
  		return 0;
  	}

  	if (!expand_corename(cn, cn->size + need - free + 1))

  		goto again;

  	return -ENOMEM;

  }

  static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...)

  {
  	va_list arg;
  	int ret;
  
  	va_start(arg, fmt);
  	ret = cn_vprintf(cn, fmt, arg);
  	va_end(arg);
  
  	return ret;
  }

  static __printf(2, 3)
  int cn_esc_printf(struct core_name *cn, const char *fmt, ...)

  {

  	int cur = cn->used;
  	va_list arg;
  	int ret;
  
  	va_start(arg, fmt);
  	ret = cn_vprintf(cn, fmt, arg);
  	va_end(arg);

  	if (ret == 0) {
  		/*
  		 * Ensure that this coredump name component can't cause the
  		 * resulting corefile path to consist of a ".." or ".".
  		 */
  		if ((cn->used - cur == 1 && cn->corename[cur] == '.') ||
  				(cn->used - cur == 2 && cn->corename[cur] == '.'
  				&& cn->corename[cur+1] == '.'))
  			cn->corename[cur] = '!';
  
  		/*
  		 * Empty names are fishy and could be used to create a "//" in a
  		 * corefile name, causing the coredump to happen one directory
  		 * level too high. Enforce that all components of the core
  		 * pattern are at least one character long.
  		 */
  		if (cn->used == cur)
  			ret = cn_printf(cn, "!");
  	}

  	for (; cur < cn->used; ++cur) {
  		if (cn->corename[cur] == '/')
  			cn->corename[cur] = '!';
  	}
  	return ret;

  }

  static int cn_print_exe_file(struct core_name *cn, bool name_only)

  {
  	struct file *exe_file;

  	char *pathbuf, *path, *ptr;

  	int ret;
  
  	exe_file = get_mm_exe_file(current->mm);

  	if (!exe_file)
  		return cn_esc_printf(cn, "%s (path unknown)", current->comm);

  	pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);

  	if (!pathbuf) {
  		ret = -ENOMEM;
  		goto put_exe_file;
  	}

  	path = file_path(exe_file, pathbuf, PATH_MAX);

  	if (IS_ERR(path)) {
  		ret = PTR_ERR(path);
  		goto free_buf;
  	}

  	if (name_only) {
  		ptr = strrchr(path, '/');
  		if (ptr)
  			path = ptr + 1;
  	}

  	ret = cn_esc_printf(cn, "%s", path);

  
  free_buf:
  	kfree(pathbuf);
  put_exe_file:
  	fput(exe_file);
  	return ret;
  }
  
  /* format_corename will inspect the pattern parameter, and output a
   * name into corename, which must have space for at least
   * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
   */

  static int format_corename(struct core_name *cn, struct coredump_params *cprm,
  			   size_t **argv, int *argc)

  {
  	const struct cred *cred = current_cred();
  	const char *pat_ptr = core_pattern;
  	int ispipe = (*pat_ptr == '|');

  	bool was_space = false;

  	int pid_in_pattern = 0;
  	int err = 0;

  	cn->used = 0;

  	cn->corename = NULL;
  	if (expand_corename(cn, core_name_size))

  		return -ENOMEM;

  	cn->corename[0] = '\0';

  	if (ispipe) {
  		int argvs = sizeof(core_pattern) / 2;
  		(*argv) = kmalloc_array(argvs, sizeof(**argv), GFP_KERNEL);
  		if (!(*argv))
  			return -ENOMEM;
  		(*argv)[(*argc)++] = 0;

  		++pat_ptr;

  		if (!(*pat_ptr))
  			return -ENOMEM;

  	}

  
  	/* Repeat as long as we have more pattern to process and more output
  	   space */
  	while (*pat_ptr) {

  		/*
  		 * Split on spaces before doing template expansion so that
  		 * %e and %E don't get split if they have spaces in them
  		 */
  		if (ispipe) {
  			if (isspace(*pat_ptr)) {

  				if (cn->used != 0)
  					was_space = true;

  				pat_ptr++;
  				continue;
  			} else if (was_space) {
  				was_space = false;
  				err = cn_printf(cn, "%c", '\0');
  				if (err)
  					return err;
  				(*argv)[(*argc)++] = cn->used;
  			}
  		}

  		if (*pat_ptr != '%') {

  			err = cn_printf(cn, "%c", *pat_ptr++);
  		} else {
  			switch (*++pat_ptr) {
  			/* single % at the end, drop that */
  			case 0:
  				goto out;
  			/* Double percent, output one percent */
  			case '%':
  				err = cn_printf(cn, "%c", '%');
  				break;
  			/* pid */
  			case 'p':
  				pid_in_pattern = 1;
  				err = cn_printf(cn, "%d",
  					      task_tgid_vnr(current));
  				break;

  			/* global pid */
  			case 'P':
  				err = cn_printf(cn, "%d",
  					      task_tgid_nr(current));
  				break;

  			case 'i':
  				err = cn_printf(cn, "%d",
  					      task_pid_vnr(current));
  				break;
  			case 'I':
  				err = cn_printf(cn, "%d",
  					      task_pid_nr(current));
  				break;

  			/* uid */
  			case 'u':

  				err = cn_printf(cn, "%u",
  						from_kuid(&init_user_ns,
  							  cred->uid));

  				break;
  			/* gid */
  			case 'g':

  				err = cn_printf(cn, "%u",
  						from_kgid(&init_user_ns,
  							  cred->gid));

  				break;

  			case 'd':
  				err = cn_printf(cn, "%d",
  					__get_dumpable(cprm->mm_flags));
  				break;

  			/* signal that caused the coredump */
  			case 's':

  				err = cn_printf(cn, "%d",
  						cprm->siginfo->si_signo);

  				break;
  			/* UNIX time of coredump */
  			case 't': {

  				time64_t time;
  
  				time = ktime_get_real_seconds();
  				err = cn_printf(cn, "%lld", time);

  				break;
  			}
  			/* hostname */

  			case 'h':

  				down_read(&uts_sem);

  				err = cn_esc_printf(cn, "%s",

  					      utsname()->nodename);
  				up_read(&uts_sem);

  				break;

  			/* executable, could be changed by prctl PR_SET_NAME etc */

  			case 'e':
  				err = cn_esc_printf(cn, "%s", current->comm);

  				break;

  			/* file name of executable */
  			case 'f':
  				err = cn_print_exe_file(cn, true);
  				break;

  			case 'E':

  				err = cn_print_exe_file(cn, false);

  				break;
  			/* core limit size */
  			case 'c':
  				err = cn_printf(cn, "%lu",
  					      rlimit(RLIMIT_CORE));
  				break;
  			default:
  				break;
  			}
  			++pat_ptr;
  		}
  
  		if (err)
  			return err;
  	}

  out:

  	/* Backward compatibility with core_uses_pid:
  	 *
  	 * If core_pattern does not include a %p (as is the default)
  	 * and core_uses_pid is set, then .%pid will be appended to
  	 * the filename. Do not do this for piped commands. */
  	if (!ispipe && !pid_in_pattern && core_uses_pid) {
  		err = cn_printf(cn, ".%d", task_tgid_vnr(current));
  		if (err)
  			return err;
  	}

  	return ispipe;
  }

  static int zap_process(struct task_struct *start, int exit_code, int flags)

  {
  	struct task_struct *t;
  	int nr = 0;

  	/* ignore all signals except SIGKILL, see prepare_signal() */
  	start->signal->flags = SIGNAL_GROUP_COREDUMP | flags;

  	start->signal->group_exit_code = exit_code;
  	start->signal->group_stop_count = 0;

  	for_each_thread(start, t) {

  		task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
  		if (t != current && t->mm) {
  			sigaddset(&t->pending.signal, SIGKILL);
  			signal_wake_up(t, 1);
  			nr++;
  		}

  	}

  
  	return nr;
  }

  static int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
  			struct core_state *core_state, int exit_code)

  {
  	struct task_struct *g, *p;
  	unsigned long flags;
  	int nr = -EAGAIN;
  
  	spin_lock_irq(&tsk->sighand->siglock);
  	if (!signal_group_exit(tsk->signal)) {
  		mm->core_state = core_state;

  		tsk->signal->group_exit_task = tsk;

  		nr = zap_process(tsk, exit_code, 0);

  		clear_tsk_thread_flag(tsk, TIF_SIGPENDING);

  	}
  	spin_unlock_irq(&tsk->sighand->siglock);
  	if (unlikely(nr < 0))
  		return nr;

  	tsk->flags |= PF_DUMPCORE;

  	if (atomic_read(&mm->mm_users) == nr + 1)
  		goto done;
  	/*
  	 * We should find and kill all tasks which use this mm, and we should
  	 * count them correctly into ->nr_threads. We don't take tasklist
  	 * lock, but this is safe wrt:
  	 *
  	 * fork:
  	 *	None of sub-threads can fork after zap_process(leader). All
  	 *	processes which were created before this point should be
  	 *	visible to zap_threads() because copy_process() adds the new
  	 *	process to the tail of init_task.tasks list, and lock/unlock
  	 *	of ->siglock provides a memory barrier.
  	 *
  	 * do_exit:

  	 *	The caller holds mm->mmap_lock. This means that the task which

  	 *	uses this mm can't pass exit_mm(), so it can't exit or clear
  	 *	its ->mm.
  	 *
  	 * de_thread:
  	 *	It does list_replace_rcu(&leader->tasks, &current->tasks),
  	 *	we must see either old or new leader, this does not matter.
  	 *	However, it can change p->sighand, so lock_task_sighand(p)

  	 *	must be used. Since p->mm != NULL and we hold ->mmap_lock

  	 *	it can't fail.
  	 *
  	 *	Note also that "g" can be the old leader with ->mm == NULL
  	 *	and already unhashed and thus removed from ->thread_group.
  	 *	This is OK, __unhash_process()->list_del_rcu() does not
  	 *	clear the ->next pointer, we will find the new leader via
  	 *	next_thread().
  	 */
  	rcu_read_lock();
  	for_each_process(g) {
  		if (g == tsk->group_leader)
  			continue;
  		if (g->flags & PF_KTHREAD)
  			continue;

  
  		for_each_thread(g, p) {
  			if (unlikely(!p->mm))
  				continue;
  			if (unlikely(p->mm == mm)) {
  				lock_task_sighand(p, &flags);
  				nr += zap_process(p, exit_code,
  							SIGNAL_GROUP_EXIT);
  				unlock_task_sighand(p, &flags);

  			}

  			break;
  		}

  	}
  	rcu_read_unlock();
  done:
  	atomic_set(&core_state->nr_threads, nr);
  	return nr;
  }
  
  static int coredump_wait(int exit_code, struct core_state *core_state)
  {
  	struct task_struct *tsk = current;
  	struct mm_struct *mm = tsk->mm;
  	int core_waiters = -EBUSY;
  
  	init_completion(&core_state->startup);
  	core_state->dumper.task = tsk;
  	core_state->dumper.next = NULL;

  	if (mmap_write_lock_killable(mm))

  		return -EINTR;

  	if (!mm->core_state)
  		core_waiters = zap_threads(tsk, mm, core_state, exit_code);

  	mmap_write_unlock(mm);

  
  	if (core_waiters > 0) {
  		struct core_thread *ptr;

  		freezer_do_not_count();

  		wait_for_completion(&core_state->startup);

  		freezer_count();

  		/*
  		 * Wait for all the threads to become inactive, so that
  		 * all the thread context (extended register state, like
  		 * fpu etc) gets copied to the memory.
  		 */
  		ptr = core_state->dumper.next;
  		while (ptr != NULL) {
  			wait_task_inactive(ptr->task, 0);
  			ptr = ptr->next;
  		}
  	}
  
  	return core_waiters;
  }

  static void coredump_finish(struct mm_struct *mm, bool core_dumped)

  {
  	struct core_thread *curr, *next;
  	struct task_struct *task;

  	spin_lock_irq(&current->sighand->siglock);

  	if (core_dumped && !__fatal_signal_pending(current))
  		current->signal->group_exit_code |= 0x80;

  	current->signal->group_exit_task = NULL;
  	current->signal->flags = SIGNAL_GROUP_EXIT;
  	spin_unlock_irq(&current->sighand->siglock);

  	next = mm->core_state->dumper.next;
  	while ((curr = next) != NULL) {
  		next = curr->next;
  		task = curr->task;
  		/*
  		 * see exit_mm(), curr->task must not see
  		 * ->task == NULL before we read ->next.
  		 */
  		smp_mb();
  		curr->task = NULL;
  		wake_up_process(task);
  	}
  
  	mm->core_state = NULL;
  }

  static bool dump_interrupted(void)
  {
  	/*
  	 * SIGKILL or freezing() interrupt the coredumping. Perhaps we
  	 * can do try_to_freeze() and check __fatal_signal_pending(),
  	 * but then we need to teach dump_write() to restart and clear
  	 * TIF_SIGPENDING.
  	 */
  	return signal_pending(current);
  }

  static void wait_for_dump_helpers(struct file *file)
  {

  	struct pipe_inode_info *pipe = file->private_data;

  
  	pipe_lock(pipe);
  	pipe->readers++;
  	pipe->writers--;

  	wake_up_interruptible_sync(&pipe->rd_wait);

  	kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
  	pipe_unlock(pipe);

  	/*
  	 * We actually want wait_event_freezable() but then we need
  	 * to clear TIF_SIGPENDING and improve dump_interrupted().
  	 */

  	wait_event_interruptible(pipe->rd_wait, pipe->readers == 1);

  	pipe_lock(pipe);

  	pipe->readers--;
  	pipe->writers++;
  	pipe_unlock(pipe);

  }
  
  /*
   * umh_pipe_setup
   * helper function to customize the process used
   * to collect the core in userspace.  Specifically
   * it sets up a pipe and installs it as fd 0 (stdin)
   * for the process.  Returns 0 on success, or
   * PTR_ERR on failure.
   * Note that it also sets the core limit to 1.  This
   * is a special value that we use to trap recursive
   * core dumps
   */
  static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
  {
  	struct file *files[2];
  	struct coredump_params *cp = (struct coredump_params *)info->data;
  	int err = create_pipe_files(files, 0);
  	if (err)
  		return err;
  
  	cp->file = files[1];

  	err = replace_fd(0, files[0], 0);
  	fput(files[0]);

  	/* and disallow core files too */
  	current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};

  	return err;

  }

  void do_coredump(const kernel_siginfo_t *siginfo)

  {
  	struct core_state core_state;
  	struct core_name cn;
  	struct mm_struct *mm = current->mm;
  	struct linux_binfmt * binfmt;
  	const struct cred *old_cred;
  	struct cred *cred;
  	int retval = 0;

  	int ispipe;

  	size_t *argv = NULL;
  	int argc = 0;

  	struct files_struct *displaced;

  	/* require nonrelative corefile path and be extra careful */
  	bool need_suid_safe = false;

  	bool core_dumped = false;

  	static atomic_t core_dump_count = ATOMIC_INIT(0);
  	struct coredump_params cprm = {

  		.siginfo = siginfo,

  		.regs = signal_pt_regs(),

  		.limit = rlimit(RLIMIT_CORE),
  		/*
  		 * We must use the same mm->flags while dumping core to avoid
  		 * inconsistency of bit flags, since this flag is not protected
  		 * by any locks.
  		 */
  		.mm_flags = mm->flags,
  	};

  	audit_core_dumps(siginfo->si_signo);

  
  	binfmt = mm->binfmt;
  	if (!binfmt || !binfmt->core_dump)
  		goto fail;
  	if (!__get_dumpable(cprm.mm_flags))
  		goto fail;
  
  	cred = prepare_creds();
  	if (!cred)
  		goto fail;
  	/*
  	 * We cannot trust fsuid as being the "true" uid of the process
  	 * nor do we know its entire history. We only know it was tainted
  	 * so we dump it as root in mode 2, and only into a controlled
  	 * environment (pipe handler or fully qualified path).
  	 */

  	if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) {

  		/* Setuid core dump mode */

  		cred->fsuid = GLOBAL_ROOT_UID;	/* Dump root private */

  		need_suid_safe = true;

  	}

  	retval = coredump_wait(siginfo->si_signo, &core_state);

  	if (retval < 0)
  		goto fail_creds;
  
  	old_cred = override_creds(cred);

  	ispipe = format_corename(&cn, &cprm, &argv, &argc);

  	if (ispipe) {

  		int argi;

  		int dump_count;
  		char **helper_argv;

  		struct subprocess_info *sub_info;

  
  		if (ispipe < 0) {
  			printk(KERN_WARNING "format_corename failed
  ");
  			printk(KERN_WARNING "Aborting core
  ");

  			goto fail_unlock;

  		}
  
  		if (cprm.limit == 1) {
  			/* See umh_pipe_setup() which sets RLIMIT_CORE = 1.
  			 *
  			 * Normally core limits are irrelevant to pipes, since
  			 * we're not writing to the file system, but we use

  			 * cprm.limit of 1 here as a special value, this is a

  			 * consistent way to catch recursive crashes.
  			 * We can still crash if the core_pattern binary sets
  			 * RLIM_CORE = !1, but it runs as root, and can do
  			 * lots of stupid things.
  			 *
  			 * Note that we use task_tgid_vnr here to grab the pid
  			 * of the process group leader.  That way we get the
  			 * right pid if a thread in a multi-threaded
  			 * core_pattern process dies.
  			 */
  			printk(KERN_WARNING
  				"Process %d(%s) has RLIMIT_CORE set to 1
  ",
  				task_tgid_vnr(current), current->comm);
  			printk(KERN_WARNING "Aborting core
  ");
  			goto fail_unlock;
  		}
  		cprm.limit = RLIM_INFINITY;
  
  		dump_count = atomic_inc_return(&core_dump_count);
  		if (core_pipe_limit && (core_pipe_limit < dump_count)) {
  			printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit
  ",
  			       task_tgid_vnr(current), current->comm);
  			printk(KERN_WARNING "Skipping core dump
  ");
  			goto fail_dropcount;
  		}

  		helper_argv = kmalloc_array(argc + 1, sizeof(*helper_argv),
  					    GFP_KERNEL);

  		if (!helper_argv) {
  			printk(KERN_WARNING "%s failed to allocate memory
  ",
  			       __func__);
  			goto fail_dropcount;
  		}

  		for (argi = 0; argi < argc; argi++)
  			helper_argv[argi] = cn.corename + argv[argi];
  		helper_argv[argi] = NULL;

  		retval = -ENOMEM;
  		sub_info = call_usermodehelper_setup(helper_argv[0],
  						helper_argv, NULL, GFP_KERNEL,
  						umh_pipe_setup, NULL, &cprm);
  		if (sub_info)
  			retval = call_usermodehelper_exec(sub_info,
  							  UMH_WAIT_EXEC);

  		kfree(helper_argv);

  		if (retval) {

  			printk(KERN_INFO "Core dump to |%s pipe failed
  ",

  			       cn.corename);
  			goto close_fail;

  		}

  	} else {
  		struct inode *inode;

  		int open_flags = O_CREAT | O_RDWR | O_NOFOLLOW |
  				 O_LARGEFILE | O_EXCL;

  
  		if (cprm.limit < binfmt->min_coredump)
  			goto fail_unlock;

  		if (need_suid_safe && cn.corename[0] != '/') {

  			printk(KERN_WARNING "Pid %d(%s) can only dump core "\
  				"to fully qualified path!
  ",
  				task_tgid_vnr(current), current->comm);
  			printk(KERN_WARNING "Skipping core dump
  ");
  			goto fail_unlock;
  		}

  		/*
  		 * Unlink the file if it exists unless this is a SUID
  		 * binary - in that case, we're running around with root
  		 * privs and don't want to unlink another user's coredump.
  		 */
  		if (!need_suid_safe) {

  			/*
  			 * If it doesn't exist, that's fine. If there's some
  			 * other problem, we'll catch it at the filp_open().
  			 */

  			do_unlinkat(AT_FDCWD, getname_kernel(cn.corename));

  		}
  
  		/*
  		 * There is a race between unlinking and creating the
  		 * file, but if that causes an EEXIST here, that's
  		 * fine - another process raced with us while creating
  		 * the corefile, and the other process won. To userspace,
  		 * what matters is that at least one of the two processes
  		 * writes its coredump successfully, not which one.
  		 */

  		if (need_suid_safe) {
  			/*
  			 * Using user namespaces, normal user tasks can change
  			 * their current->fs->root to point to arbitrary
  			 * directories. Since the intention of the "only dump
  			 * with a fully qualified path" rule is to control where
  			 * coredumps may be placed using root privileges,
  			 * current->fs->root must not be used. Instead, use the
  			 * root directory of init_task.
  			 */
  			struct path root;
  
  			task_lock(&init_task);
  			get_fs_root(init_task.fs, &root);
  			task_unlock(&init_task);
  			cprm.file = file_open_root(root.dentry, root.mnt,
  				cn.corename, open_flags, 0600);
  			path_put(&root);
  		} else {
  			cprm.file = filp_open(cn.corename, open_flags, 0600);
  		}

  		if (IS_ERR(cprm.file))
  			goto fail_unlock;

  		inode = file_inode(cprm.file);

  		if (inode->i_nlink > 1)
  			goto close_fail;
  		if (d_unhashed(cprm.file->f_path.dentry))
  			goto close_fail;
  		/*
  		 * AK: actually i see no reason to not allow this for named
  		 * pipes etc, but keep the previous behaviour for now.
  		 */
  		if (!S_ISREG(inode->i_mode))
  			goto close_fail;
  		/*

  		 * Don't dump core if the filesystem changed owner or mode
  		 * of the file during file creation. This is an issue when
  		 * a process dumps core while its cwd is e.g. on a vfat
  		 * filesystem.

  		 */
  		if (!uid_eq(inode->i_uid, current_fsuid()))
  			goto close_fail;

  		if ((inode->i_mode & 0677) != 0600)
  			goto close_fail;

  		if (!(cprm.file->f_mode & FMODE_CAN_WRITE))

  			goto close_fail;
  		if (do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file))
  			goto close_fail;
  	}
  
  	/* get us an unshared descriptor table; almost always a no-op */
  	retval = unshare_files(&displaced);
  	if (retval)
  		goto close_fail;
  	if (displaced)
  		put_files_struct(displaced);

  	if (!dump_interrupted()) {

  		/*
  		 * umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would
  		 * have this set to NULL.
  		 */
  		if (!cprm.file) {
  			pr_info("Core dump to |%s disabled
  ", cn.corename);
  			goto close_fail;
  		}

  		file_start_write(cprm.file);
  		core_dumped = binfmt->core_dump(&cprm);
  		file_end_write(cprm.file);
  	}

  	if (ispipe && core_pipe_limit)
  		wait_for_dump_helpers(cprm.file);
  close_fail:
  	if (cprm.file)
  		filp_close(cprm.file, NULL);
  fail_dropcount:
  	if (ispipe)
  		atomic_dec(&core_dump_count);
  fail_unlock:

  	kfree(argv);

  	kfree(cn.corename);

  	coredump_finish(mm, core_dumped);

  	revert_creds(old_cred);
  fail_creds:
  	put_cred(cred);
  fail:
  	return;
  }
  
  /*
   * Core dumping helper functions.  These are the only things you should
   * do on a core-file: use only these functions to write out all the
   * necessary info.
   */

  int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
  {
  	struct file *file = cprm->file;

  	loff_t pos = file->f_pos;
  	ssize_t n;

  	if (cprm->written + nr > cprm->limit)

  		return 0;

  
  
  	if (dump_interrupted())
  		return 0;
  	n = __kernel_write(file, addr, nr, &pos);
  	if (n != nr)
  		return 0;
  	file->f_pos = pos;
  	cprm->written += n;
  	cprm->pos += n;

  	return 1;
  }
  EXPORT_SYMBOL(dump_emit);

  int dump_skip(struct coredump_params *cprm, size_t nr)

  {

  	static char zeroes[PAGE_SIZE];
  	struct file *file = cprm->file;

  	if (file->f_op->llseek && file->f_op->llseek != no_llseek) {

  		if (dump_interrupted() ||

  		    file->f_op->llseek(file, nr, SEEK_CUR) < 0)

  			return 0;

  		cprm->pos += nr;

  		return 1;

  	} else {

  		while (nr > PAGE_SIZE) {
  			if (!dump_emit(cprm, zeroes, PAGE_SIZE))
  				return 0;
  			nr -= PAGE_SIZE;

  		}

  		return dump_emit(cprm, zeroes, nr);

  	}

  }

  EXPORT_SYMBOL(dump_skip);

  #ifdef CONFIG_ELF_CORE
  int dump_user_range(struct coredump_params *cprm, unsigned long start,
  		    unsigned long len)
  {
  	unsigned long addr;
  
  	for (addr = start; addr < start + len; addr += PAGE_SIZE) {
  		struct page *page;
  		int stop;
  
  		/*
  		 * To avoid having to allocate page tables for virtual address
  		 * ranges that have never been used yet, and also to make it
  		 * easy to generate sparse core files, use a helper that returns
  		 * NULL when encountering an empty page table entry that would
  		 * otherwise have been filled with the zero page.
  		 */
  		page = get_dump_page(addr);
  		if (page) {
  			void *kaddr = kmap(page);
  
  			stop = !dump_emit(cprm, kaddr, PAGE_SIZE);
  			kunmap(page);
  			put_page(page);
  		} else {
  			stop = !dump_skip(cprm, PAGE_SIZE);
  		}
  		if (stop)
  			return 0;
  	}
  	return 1;
  }
  #endif

  int dump_align(struct coredump_params *cprm, int align)
  {

  	unsigned mod = cprm->pos & (align - 1);

  	if (align & (align - 1))

  		return 0;
  	return mod ? dump_skip(cprm, align - mod) : 1;

  }
  EXPORT_SYMBOL(dump_align);

  
  /*
   * Ensures that file size is big enough to contain the current file
   * postion. This prevents gdb from complaining about a truncated file
   * if the last "write" to the file was dump_skip.
   */
  void dump_truncate(struct coredump_params *cprm)
  {
  	struct file *file = cprm->file;
  	loff_t offset;
  
  	if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
  		offset = file->f_op->llseek(file, 0, SEEK_CUR);
  		if (i_size_read(file->f_mapping->host) < offset)
  			do_truncate(file->f_path.dentry, offset, 0, file);
  	}
  }
  EXPORT_SYMBOL(dump_truncate);

  
  /*
   * The purpose of always_dump_vma() is to make sure that special kernel mappings
   * that are useful for post-mortem analysis are included in every core dump.
   * In that way we ensure that the core dump is fully interpretable later
   * without matching up the same kernel and hardware config to see what PC values
   * meant. These special mappings include - vDSO, vsyscall, and other
   * architecture specific mappings
   */
  static bool always_dump_vma(struct vm_area_struct *vma)
  {
  	/* Any vsyscall mappings? */
  	if (vma == get_gate_vma(vma->vm_mm))
  		return true;
  
  	/*
  	 * Assume that all vmas with a .name op should always be dumped.
  	 * If this changes, a new vm_ops field can easily be added.
  	 */
  	if (vma->vm_ops && vma->vm_ops->name && vma->vm_ops->name(vma))
  		return true;
  
  	/*
  	 * arch_vma_name() returns non-NULL for special architecture mappings,
  	 * such as vDSO sections.
  	 */
  	if (arch_vma_name(vma))
  		return true;
  
  	return false;
  }
  
  /*
   * Decide how much of @vma's contents should be included in a core dump.
   */

  static unsigned long vma_dump_size(struct vm_area_struct *vma,
  				   unsigned long mm_flags)

  {
  #define FILTER(type)	(mm_flags & (1UL << MMF_DUMP_##type))
  
  	/* always dump the vdso and vsyscall sections */
  	if (always_dump_vma(vma))
  		goto whole;
  
  	if (vma->vm_flags & VM_DONTDUMP)
  		return 0;
  
  	/* support for DAX */
  	if (vma_is_dax(vma)) {
  		if ((vma->vm_flags & VM_SHARED) && FILTER(DAX_SHARED))
  			goto whole;
  		if (!(vma->vm_flags & VM_SHARED) && FILTER(DAX_PRIVATE))
  			goto whole;
  		return 0;
  	}
  
  	/* Hugetlb memory check */
  	if (is_vm_hugetlb_page(vma)) {
  		if ((vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_SHARED))
  			goto whole;
  		if (!(vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_PRIVATE))
  			goto whole;
  		return 0;
  	}
  
  	/* Do not dump I/O mapped devices or special mappings */
  	if (vma->vm_flags & VM_IO)
  		return 0;
  
  	/* By default, dump shared memory if mapped from an anonymous file. */
  	if (vma->vm_flags & VM_SHARED) {
  		if (file_inode(vma->vm_file)->i_nlink == 0 ?
  		    FILTER(ANON_SHARED) : FILTER(MAPPED_SHARED))
  			goto whole;
  		return 0;
  	}
  
  	/* Dump segments that have been written to.  */
  	if ((!IS_ENABLED(CONFIG_MMU) || vma->anon_vma) && FILTER(ANON_PRIVATE))
  		goto whole;
  	if (vma->vm_file == NULL)
  		return 0;
  
  	if (FILTER(MAPPED_PRIVATE))
  		goto whole;
  
  	/*
  	 * If this is the beginning of an executable file mapping,
  	 * dump the first page to aid in determining what was mapped here.
  	 */
  	if (FILTER(ELF_HEADERS) &&
  	    vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ) &&
  	    (READ_ONCE(file_inode(vma->vm_file)->i_mode) & 0111) != 0)
  		return PAGE_SIZE;
  
  #undef	FILTER
  
  	return 0;
  
  whole:
  	return vma->vm_end - vma->vm_start;
  }

  
  static struct vm_area_struct *first_vma(struct task_struct *tsk,
  					struct vm_area_struct *gate_vma)
  {
  	struct vm_area_struct *ret = tsk->mm->mmap;
  
  	if (ret)
  		return ret;
  	return gate_vma;
  }
  
  /*
   * Helper function for iterating across a vma list.  It ensures that the caller
   * will visit `gate_vma' prior to terminating the search.
   */
  static struct vm_area_struct *next_vma(struct vm_area_struct *this_vma,
  				       struct vm_area_struct *gate_vma)
  {
  	struct vm_area_struct *ret;
  
  	ret = this_vma->vm_next;
  	if (ret)
  		return ret;
  	if (this_vma == gate_vma)
  		return NULL;
  	return gate_vma;
  }
  
  /*
   * Under the mmap_lock, take a snapshot of relevant information about the task's
   * VMAs.
   */
  int dump_vma_snapshot(struct coredump_params *cprm, int *vma_count,
  		      struct core_vma_metadata **vma_meta,
  		      size_t *vma_data_size_ptr)
  {
  	struct vm_area_struct *vma, *gate_vma;
  	struct mm_struct *mm = current->mm;
  	int i;
  	size_t vma_data_size = 0;
  
  	/*
  	 * Once the stack expansion code is fixed to not change VMA bounds
  	 * under mmap_lock in read mode, this can be changed to take the
  	 * mmap_lock in read mode.
  	 */
  	if (mmap_write_lock_killable(mm))
  		return -EINTR;
  
  	gate_vma = get_gate_vma(mm);
  	*vma_count = mm->map_count + (gate_vma ? 1 : 0);
  
  	*vma_meta = kvmalloc_array(*vma_count, sizeof(**vma_meta), GFP_KERNEL);
  	if (!*vma_meta) {
  		mmap_write_unlock(mm);
  		return -ENOMEM;
  	}
  
  	for (i = 0, vma = first_vma(current, gate_vma); vma != NULL;
  			vma = next_vma(vma, gate_vma), i++) {
  		struct core_vma_metadata *m = (*vma_meta) + i;
  
  		m->start = vma->vm_start;
  		m->end = vma->vm_end;
  		m->flags = vma->vm_flags;
  		m->dump_size = vma_dump_size(vma, cprm->mm_flags);
  
  		vma_data_size += m->dump_size;
  	}
  
  	mmap_write_unlock(mm);
  
  	if (WARN_ON(i != *vma_count))
  		return -EFAULT;
  
  	*vma_data_size_ptr = vma_data_size;
  	return 0;
  }