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>
diff --git a/fs/coredump.c b/fs/coredump.c
new file mode 100644
index 0000000..f045bba
--- /dev/null
+++ b/fs/coredump.c
@@ -0,0 +1,686 @@
+#include <linux/slab.h>
+#include <linux/file.h>
+#include <linux/fdtable.h>
+#include <linux/mm.h>
+#include <linux/stat.h>
+#include <linux/fcntl.h>
+#include <linux/swap.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/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 <asm/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;
+char core_pattern[CORENAME_MAX_SIZE] = "core";
+unsigned int core_pipe_limit;
+
+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 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, ¤t->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;
+}
+
+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);