coredump: move core dump functionality into its own file

This prepares for making core dump functionality optional.

The variable "suid_dumpable" and associated functions are left in fs/exec.c
because they're used elsewhere, such as in ptrace.

Signed-off-by: Alex Kelly <alex.page.kelly@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 1 insertions, 644 deletions

diff --git a/fs/exec.c b/fs/exec.c
index beb05a9..48fb26e 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -66,19 +66,8 @@
 
 #include <trace/events/sched.h>
 
-int core_uses_pid;
-char core_pattern[CORENAME_MAX_SIZE] = "core";
-unsigned int core_pipe_limit;
 int suid_dumpable = 0;
 
-struct core_name {
-	char *corename;
-	int used, size;
-};
-static atomic_t call_count = ATOMIC_INIT(1);
-
-/* The maximal length of core_pattern is also specified in sysctl.c */
-
 static LIST_HEAD(formats);
 static DEFINE_RWLOCK(binfmt_lock);
 
@@ -1603,353 +1592,6 @@ void set_binfmt(struct linux_binfmt *new)
 
 EXPORT_SYMBOL(set_binfmt);
 
-static int expand_corename(struct core_name *cn)
-{
-	char *old_corename = cn->corename;
-
-	cn->size = CORENAME_MAX_SIZE * atomic_inc_return(&call_count);
-	cn->corename = krealloc(old_corename, cn->size, GFP_KERNEL);
-
-	if (!cn->corename) {
-		kfree(old_corename);
-		return -ENOMEM;
-	}
-
-	return 0;
-}
-
-static int cn_printf(struct core_name *cn, const char *fmt, ...)
-{
-	char *cur;
-	int need;
-	int ret;
-	va_list arg;
-
-	va_start(arg, fmt);
-	need = vsnprintf(NULL, 0, fmt, arg);
-	va_end(arg);
-
-	if (likely(need < cn->size - cn->used - 1))
-		goto out_printf;
-
-	ret = expand_corename(cn);
-	if (ret)
-		goto expand_fail;
-
-out_printf:
-	cur = cn->corename + cn->used;
-	va_start(arg, fmt);
-	vsnprintf(cur, need + 1, fmt, arg);
-	va_end(arg);
-	cn->used += need;
-	return 0;
-
-expand_fail:
-	return ret;
-}
-
-static void cn_escape(char *str)
-{
-	for (; *str; str++)
-		if (*str == '/')
-			*str = '!';
-}
-
-static int cn_print_exe_file(struct core_name *cn)
-{
-	struct file *exe_file;
-	char *pathbuf, *path;
-	int ret;
-
-	exe_file = get_mm_exe_file(current->mm);
-	if (!exe_file) {
-		char *commstart = cn->corename + cn->used;
-		ret = cn_printf(cn, "%s (path unknown)", current->comm);
-		cn_escape(commstart);
-		return ret;
-	}
-
-	pathbuf = kmalloc(PATH_MAX, GFP_TEMPORARY);
-	if (!pathbuf) {
-		ret = -ENOMEM;
-		goto put_exe_file;
-	}
-
-	path = d_path(&exe_file->f_path, pathbuf, PATH_MAX);
-	if (IS_ERR(path)) {
-		ret = PTR_ERR(path);
-		goto free_buf;
-	}
-
-	cn_escape(path);
-
-	ret = cn_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, long signr)
-{
-	const struct cred *cred = current_cred();
-	const char *pat_ptr = core_pattern;
-	int ispipe = (*pat_ptr == '|');
-	int pid_in_pattern = 0;
-	int err = 0;
-
-	cn->size = CORENAME_MAX_SIZE * atomic_read(&call_count);
-	cn->corename = kmalloc(cn->size, GFP_KERNEL);
-	cn->used = 0;
-
-	if (!cn->corename)
-		return -ENOMEM;
-
-	/* Repeat as long as we have more pattern to process and more output
-	   space */
-	while (*pat_ptr) {
-		if (*pat_ptr != '%') {
-			if (*pat_ptr == 0)
-				goto out;
-			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;
-			/* uid */
-			case 'u':
-				err = cn_printf(cn, "%d", cred->uid);
-				break;
-			/* gid */
-			case 'g':
-				err = cn_printf(cn, "%d", cred->gid);
-				break;
-			/* signal that caused the coredump */
-			case 's':
-				err = cn_printf(cn, "%ld", signr);
-				break;
-			/* UNIX time of coredump */
-			case 't': {
-				struct timeval tv;
-				do_gettimeofday(&tv);
-				err = cn_printf(cn, "%lu", tv.tv_sec);
-				break;
-			}
-			/* hostname */
-			case 'h': {
-				char *namestart = cn->corename + cn->used;
-				down_read(&uts_sem);
-				err = cn_printf(cn, "%s",
-					      utsname()->nodename);
-				up_read(&uts_sem);
-				cn_escape(namestart);
-				break;
-			}
-			/* executable */
-			case 'e': {
-				char *commstart = cn->corename + cn->used;
-				err = cn_printf(cn, "%s", current->comm);
-				cn_escape(commstart);
-				break;
-			}
-			case 'E':
-				err = cn_print_exe_file(cn);
-				break;
-			/* core limit size */
-			case 'c':
-				err = cn_printf(cn, "%lu",
-					      rlimit(RLIMIT_CORE));
-				break;
-			default:
-				break;
-			}
-			++pat_ptr;
-		}
-
-		if (err)
-			return err;
-	}
-
-	/* 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;
-	}
-out:
-	return ispipe;
-}
-
-static int zap_process(struct task_struct *start, int exit_code)
-{
-	struct task_struct *t;
-	int nr = 0;
-
-	start->signal->flags = SIGNAL_GROUP_EXIT;
-	start->signal->group_exit_code = exit_code;
-	start->signal->group_stop_count = 0;
-
-	t = start;
-	do {
-		task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
-		if (t != current && t->mm) {
-			sigaddset(&t->pending.signal, SIGKILL);
-			signal_wake_up(t, 1);
-			nr++;
-		}
-	} while_each_thread(start, t);
-
-	return nr;
-}
-
-static inline 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;
-		nr = zap_process(tsk, exit_code);
-	}
-	spin_unlock_irq(&tsk->sighand->siglock);
-	if (unlikely(nr < 0))
-		return nr;
-
-	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_sem. 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_sem
-	 *	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;
-		p = g;
-		do {
-			if (p->mm) {
-				if (unlikely(p->mm == mm)) {
-					lock_task_sighand(p, &flags);
-					nr += zap_process(p, exit_code);
-					unlock_task_sighand(p, &flags);
-				}
-				break;
-			}
-		} while_each_thread(g, p);
-	}
-	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;
-
-	down_write(&mm->mmap_sem);
-	if (!mm->core_state)
-		core_waiters = zap_threads(tsk, mm, core_state, exit_code);
-	up_write(&mm->mmap_sem);
-
-	if (core_waiters > 0) {
-		struct core_thread *ptr;
-
-		wait_for_completion(&core_state->startup);
-		/*
-		 * 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)
-{
-	struct core_thread *curr, *next;
-	struct task_struct *task;
-
-	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;
-}
-
 /*
  * set_dumpable converts traditional three-value dumpable to two flags and
  * stores them into mm->flags.  It modifies lower two bits of mm->flags, but
@@ -1991,7 +1633,7 @@ void set_dumpable(struct mm_struct *mm, int value)
 	}
 }
 
-static int __get_dumpable(unsigned long mm_flags)
+int __get_dumpable(unsigned long mm_flags)
 {
 	int ret;
 
@@ -2003,288 +1645,3 @@ int get_dumpable(struct mm_struct *mm)
 {
 	return __get_dumpable(mm->flags);
 }
-
-static void wait_for_dump_helpers(struct file *file)
-{
-	struct pipe_inode_info *pipe;
-
-	pipe = file->f_path.dentry->d_inode->i_pipe;
-
-	pipe_lock(pipe);
-	pipe->readers++;
-	pipe->writers--;
-
-	while ((pipe->readers > 1) && (!signal_pending(current))) {
-		wake_up_interruptible_sync(&pipe->wait);
-		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
-		pipe_wait(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];
-
-	replace_fd(0, files[0], 0);
-	/* and disallow core files too */
-	current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
-
-	return 0;
-}
-
-void do_coredump(long signr, int exit_code, struct pt_regs *regs)
-{
-	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 flag = 0;
-	int ispipe;
-	struct files_struct *displaced;
-	bool need_nonrelative = false;
-	static atomic_t core_dump_count = ATOMIC_INIT(0);
-	struct coredump_params cprm = {
-		.signr = signr,
-		.regs = 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(signr);
-
-	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_DUMPABLE_SAFE) {
-		/* Setuid core dump mode */
-		flag = O_EXCL;		/* Stop rewrite attacks */
-		cred->fsuid = GLOBAL_ROOT_UID;	/* Dump root private */
-		need_nonrelative = true;
-	}
-
-	retval = coredump_wait(exit_code, &core_state);
-	if (retval < 0)
-		goto fail_creds;
-
-	old_cred = override_creds(cred);
-
-	/*
-	 * Clear any false indication of pending signals that might
-	 * be seen by the filesystem code called to write the core file.
-	 */
-	clear_thread_flag(TIF_SIGPENDING);
-
-	ispipe = format_corename(&cn, signr);
-
- 	if (ispipe) {
-		int dump_count;
-		char **helper_argv;
-
-		if (ispipe < 0) {
-			printk(KERN_WARNING "format_corename failed\n");
-			printk(KERN_WARNING "Aborting core\n");
-			goto fail_corename;
-		}
-
-		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 speacial 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\n",
-				task_tgid_vnr(current), current->comm);
-			printk(KERN_WARNING "Aborting core\n");
-			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\n",
-			       task_tgid_vnr(current), current->comm);
-			printk(KERN_WARNING "Skipping core dump\n");
-			goto fail_dropcount;
-		}
-
-		helper_argv = argv_split(GFP_KERNEL, cn.corename+1, NULL);
-		if (!helper_argv) {
-			printk(KERN_WARNING "%s failed to allocate memory\n",
-			       __func__);
-			goto fail_dropcount;
-		}
-
-		retval = call_usermodehelper_fns(helper_argv[0], helper_argv,
-					NULL, UMH_WAIT_EXEC, umh_pipe_setup,
-					NULL, &cprm);
-		argv_free(helper_argv);
-		if (retval) {
- 			printk(KERN_INFO "Core dump to %s pipe failed\n",
-			       cn.corename);
-			goto close_fail;
- 		}
-	} else {
-		struct inode *inode;
-
-		if (cprm.limit < binfmt->min_coredump)
-			goto fail_unlock;
-
-		if (need_nonrelative && cn.corename[0] != '/') {
-			printk(KERN_WARNING "Pid %d(%s) can only dump core "\
-				"to fully qualified path!\n",
-				task_tgid_vnr(current), current->comm);
-			printk(KERN_WARNING "Skipping core dump\n");
-			goto fail_unlock;
-		}
-
-		cprm.file = filp_open(cn.corename,
-				 O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag,
-				 0600);
-		if (IS_ERR(cprm.file))
-			goto fail_unlock;
-
-		inode = cprm.file->f_path.dentry->d_inode;
-		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;
-		/*
-		 * Dont allow local users get cute and trick others to coredump
-		 * into their pre-created files.
-		 */
-		if (!uid_eq(inode->i_uid, current_fsuid()))
-			goto close_fail;
-		if (!cprm.file->f_op || !cprm.file->f_op->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);
-	retval = binfmt->core_dump(&cprm);
-	if (retval)
-		current->signal->group_exit_code |= 0x80;
-
-	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(cn.corename);
-fail_corename:
-	coredump_finish(mm);
-	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_write(struct file *file, const void *addr, int nr)
-{
-	return access_ok(VERIFY_READ, addr, nr) && file->f_op->write(file, addr, nr, &file->f_pos) == nr;
-}
-EXPORT_SYMBOL(dump_write);
-
-int dump_seek(struct file *file, loff_t off)
-{
-	int ret = 1;
-
-	if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
-		if (file->f_op->llseek(file, off, SEEK_CUR) < 0)
-			return 0;
-	} else {
-		char *buf = (char *)get_zeroed_page(GFP_KERNEL);
-
-		if (!buf)
-			return 0;
-		while (off > 0) {
-			unsigned long n = off;
-
-			if (n > PAGE_SIZE)
-				n = PAGE_SIZE;
-			if (!dump_write(file, buf, n)) {
-				ret = 0;
-				break;
-			}
-			off -= n;
-		}
-		free_page((unsigned long)buf);
-	}
-	return ret;
-}
-EXPORT_SYMBOL(dump_seek);