#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/coredump.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 "coredump.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 int cn_vprintf(struct core_name *cn, const char *fmt, va_list arg) { int free, need; again: free = cn->size - cn->used; need = vsnprintf(cn->corename + cn->used, free, fmt, arg); if (need < free) { cn->used += need; return 0; } if (!expand_corename(cn, cn->size + need - free + 1)) goto again; return -ENOMEM; } static 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 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); for (; cur < cn->used; ++cur) { if (cn->corename[cur] == '/') cn->corename[cur] = '!'; } return ret; } 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) return cn_esc_printf(cn, "%s (path unknown)", current->comm); 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; } 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) { 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->used = 0; cn->corename = NULL; if (expand_corename(cn, core_name_size)) return -ENOMEM; cn->corename[0] = '\0'; if (ispipe) ++pat_ptr; /* Repeat as long as we have more pattern to process and more output space */ while (*pat_ptr) { 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; /* uid */ case 'u': err = cn_printf(cn, "%d", cred->uid); break; /* gid */ case 'g': err = cn_printf(cn, "%d", 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, "%ld", cprm->siginfo->si_signo); 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': down_read(&uts_sem); err = cn_esc_printf(cn, "%s", utsname()->nodename); up_read(&uts_sem); break; /* executable */ case 'e': err = cn_esc_printf(cn, "%s", current->comm); 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; } 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) { struct task_struct *t; int nr = 0; 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 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); tsk->signal->group_exit_task = tsk; /* ignore all signals except SIGKILL, see prepare_signal() */ tsk->signal->flags = SIGNAL_GROUP_COREDUMP; 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_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); p->signal->flags = SIGNAL_GROUP_EXIT; 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, bool core_dumped) { struct core_thread *curr, *next; struct task_struct *task; spin_lock_irq(¤t->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(¤t->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->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->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(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 flag = 0; int ispipe; struct files_struct *displaced; bool need_nonrelative = 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 */ flag = O_EXCL; /* Stop rewrite attacks */ cred->fsuid = GLOBAL_ROOT_UID; /* Dump root private */ need_nonrelative = 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); if (ispipe) { int dump_count; char **helper_argv; struct subprocess_info *sub_info; if (ispipe < 0) { printk(KERN_WARNING "format_corename failed\n"); printk(KERN_WARNING "Aborting core\n"); 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 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, NULL); if (!helper_argv) { printk(KERN_WARNING "%s failed to allocate memory\n", __func__); goto fail_dropcount; } 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); 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 = 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; /* * 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); if (!dump_interrupted()) { 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(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_write(struct file *file, const void *addr, int nr) { return !dump_interrupted() && 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 (dump_interrupted() || 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);