// 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/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/sysctl.h> #include <linux/elf.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> static bool dump_vma_snapshot(struct coredump_params *cprm); static void free_vma_snapshot(struct coredump_params *cprm); static int core_uses_pid; static unsigned int core_pipe_limit; static char core_pattern[CORENAME_MAX_SIZE] = "core"; static int core_name_size = CORENAME_MAX_SIZE; struct core_name { char *corename; int used, size; }; static int expand_corename(struct core_name *cn, int size) { char *corename; size = kmalloc_size_roundup(size); 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 = size; 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; /* CPU the task ran on */ case 'C': err = cn_printf(cn, "%d", cprm->cpu); 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; /* Allow SIGKILL, see prepare_signal() */ start->signal->flags = SIGNAL_GROUP_EXIT; 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->flags & PF_POSTCOREDUMP)) { sigaddset(&t->pending.signal, SIGKILL); signal_wake_up(t, 1); /* The vhost_worker does not particpate in coredumps */ if ((t->flags & (PF_USER_WORKER | PF_IO_WORKER)) != PF_USER_WORKER) nr++; } } return nr; } static int zap_threads(struct task_struct *tsk, struct core_state *core_state, int exit_code) { struct signal_struct *signal = tsk->signal; int nr = -EAGAIN; spin_lock_irq(&tsk->sighand->siglock); if (!(signal->flags & SIGNAL_GROUP_EXIT) && !signal->group_exec_task) { signal->core_state = core_state; nr = zap_process(tsk, exit_code); clear_tsk_thread_flag(tsk, TIF_SIGPENDING); tsk->flags |= PF_DUMPCORE; atomic_set(&core_state->nr_threads, nr); } spin_unlock_irq(&tsk->sighand->siglock); return nr; } static int coredump_wait(int exit_code, struct core_state *core_state) { struct task_struct *tsk = current; int core_waiters = -EBUSY; init_completion(&core_state->startup); core_state->dumper.task = tsk; core_state->dumper.next = NULL; core_waiters = zap_threads(tsk, core_state, exit_code); if (core_waiters > 0) { struct core_thread *ptr; wait_for_completion_state(&core_state->startup, TASK_UNINTERRUPTIBLE|TASK_FREEZABLE); /* * 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, TASK_ANY); ptr = ptr->next; } } return core_waiters; } static void coredump_finish(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; next = current->signal->core_state->dumper.next; current->signal->core_state = NULL; spin_unlock_irq(¤t->sighand->siglock); while ((curr = next) != NULL) { next = curr->next; task = curr->task; /* * see coredump_task_exit(), curr->task must not see * ->task == NULL before we read ->next. */ smp_mb(); curr->task = NULL; wake_up_process(task); } } 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 fatal_signal_pending(current) || freezing(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; /* 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, .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, .vma_meta = NULL, .cpu = raw_smp_processor_id(), }; 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\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 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\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 = kmalloc_array(argc + 1, sizeof(*helper_argv), GFP_KERNEL); if (!helper_argv) { printk(KERN_WARNING "%s failed to allocate memory\n", __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\n", cn.corename); goto close_fail; } } else { struct mnt_idmap *idmap; struct inode *inode; int open_flags = O_CREAT | O_WRONLY | 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!\n", task_tgid_vnr(current), current->comm); printk(KERN_WARNING "Skipping core dump\n"); 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, 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. */ idmap = file_mnt_idmap(cprm.file); if (!vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, inode), current_fsuid())) { pr_info_ratelimited("Core dump to %s aborted: cannot preserve file owner\n", cn.corename); goto close_fail; } if ((inode->i_mode & 0677) != 0600) { pr_info_ratelimited("Core dump to %s aborted: cannot preserve file permissions\n", cn.corename); goto close_fail; } if (!(cprm.file->f_mode & FMODE_CAN_WRITE)) goto close_fail; if (do_truncate(idmap, cprm.file->f_path.dentry, 0, 0, cprm.file)) goto close_fail; } /* get us an unshared descriptor table; almost always a no-op */ /* The cell spufs coredump code reads the file descriptor tables */ retval = unshare_files(); if (retval) goto close_fail; 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\n", cn.corename); goto close_fail; } if (!dump_vma_snapshot(&cprm)) goto close_fail; file_start_write(cprm.file); core_dumped = binfmt->core_dump(&cprm); /* * 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. */ if (cprm.to_skip) { cprm.to_skip--; dump_emit(&cprm, "", 1); } file_end_write(cprm.file); free_vma_snapshot(&cprm); } 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(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. */ static 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; } static int __dump_skip(struct coredump_params *cprm, size_t nr) { static char zeroes[PAGE_SIZE]; struct file *file = cprm->file; if (file->f_mode & FMODE_LSEEK) { if (dump_interrupted() || vfs_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); } } int dump_emit(struct coredump_params *cprm, const void *addr, int nr) { if (cprm->to_skip) { if (!__dump_skip(cprm, cprm->to_skip)) return 0; cprm->to_skip = 0; } return __dump_emit(cprm, addr, nr); } EXPORT_SYMBOL(dump_emit); void dump_skip_to(struct coredump_params *cprm, unsigned long pos) { cprm->to_skip = pos - cprm->pos; } EXPORT_SYMBOL(dump_skip_to); void dump_skip(struct coredump_params *cprm, size_t nr) { cprm->to_skip += nr; } EXPORT_SYMBOL(dump_skip); #ifdef CONFIG_ELF_CORE static int dump_emit_page(struct coredump_params *cprm, struct page *page) { struct bio_vec bvec; struct iov_iter iter; struct file *file = cprm->file; loff_t pos; ssize_t n; if (!page) return 0; if (cprm->to_skip) { if (!__dump_skip(cprm, cprm->to_skip)) return 0; cprm->to_skip = 0; } if (cprm->written + PAGE_SIZE > cprm->limit) return 0; if (dump_interrupted()) return 0; pos = file->f_pos; bvec_set_page(&bvec, page, PAGE_SIZE, 0); iov_iter_bvec(&iter, ITER_SOURCE, &bvec, 1, PAGE_SIZE); n = __kernel_write_iter(cprm->file, &iter, &pos); if (n != PAGE_SIZE) return 0; file->f_pos = pos; cprm->written += PAGE_SIZE; cprm->pos += PAGE_SIZE; return 1; } /* * If we might get machine checks from kernel accesses during the * core dump, let's get those errors early rather than during the * IO. This is not performance-critical enough to warrant having * all the machine check logic in the iovec paths. */ #ifdef copy_mc_to_kernel #define dump_page_alloc() alloc_page(GFP_KERNEL) #define dump_page_free(x) __free_page(x) static struct page *dump_page_copy(struct page *src, struct page *dst) { void *buf = kmap_local_page(src); size_t left = copy_mc_to_kernel(page_address(dst), buf, PAGE_SIZE); kunmap_local(buf); return left ? NULL : dst; } #else /* We just want to return non-NULL; it's never used. */ #define dump_page_alloc() ERR_PTR(-EINVAL) #define dump_page_free(x) ((void)(x)) static inline struct page *dump_page_copy(struct page *src, struct page *dst) { return src; } #endif int dump_user_range(struct coredump_params *cprm, unsigned long start, unsigned long len) { unsigned long addr; struct page *dump_page; dump_page = dump_page_alloc(); if (!dump_page) return 0; for (addr = start; addr < start + len; addr += PAGE_SIZE) { struct page *page; /* * 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) { int stop = !dump_emit_page(cprm, dump_page_copy(page, dump_page)); put_page(page); if (stop) { dump_page_free(dump_page); return 0; } } else { dump_skip(cprm, PAGE_SIZE); } } dump_page_free(dump_page); return 1; } #endif int dump_align(struct coredump_params *cprm, int align) { unsigned mod = (cprm->pos + cprm->to_skip) & (align - 1); if (align & (align - 1)) return 0; if (mod) cprm->to_skip += align - mod; return 1; } EXPORT_SYMBOL(dump_align); #ifdef CONFIG_SYSCTL void validate_coredump_safety(void) { if (suid_dumpable == SUID_DUMP_ROOT && core_pattern[0] != '/' && core_pattern[0] != '|') { pr_warn( "Unsafe core_pattern used with fs.suid_dumpable=2.\n" "Pipe handler or fully qualified core dump path required.\n" "Set kernel.core_pattern before fs.suid_dumpable.\n" ); } } static int proc_dostring_coredump(struct ctl_table *table, int write, void *buffer, size_t *lenp, loff_t *ppos) { int error = proc_dostring(table, write, buffer, lenp, ppos); if (!error) validate_coredump_safety(); return error; } static struct ctl_table coredump_sysctls[] = { { .procname = "core_uses_pid", .data = &core_uses_pid, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec, }, { .procname = "core_pattern", .data = core_pattern, .maxlen = CORENAME_MAX_SIZE, .mode = 0644, .proc_handler = proc_dostring_coredump, }, { .procname = "core_pipe_limit", .data = &core_pipe_limit, .maxlen = sizeof(unsigned int), .mode = 0644, .proc_handler = proc_dointvec, }, }; static int __init init_fs_coredump_sysctls(void) { register_sysctl_init("kernel", coredump_sysctls); return 0; } fs_initcall(init_fs_coredump_sysctls); #endif /* CONFIG_SYSCTL */ /* * 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; } #define DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER 1 /* * 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)) { if ((READ_ONCE(file_inode(vma->vm_file)->i_mode) & 0111) != 0) return PAGE_SIZE; /* * ELF libraries aren't always executable. * We'll want to check whether the mapping starts with the ELF * magic, but not now - we're holding the mmap lock, * so copy_from_user() doesn't work here. * Use a placeholder instead, and fix it up later in * dump_vma_snapshot(). */ return DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER; } #undef FILTER return 0; whole: return vma->vm_end - vma->vm_start; } /* * 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 *coredump_next_vma(struct vma_iterator *vmi, struct vm_area_struct *vma, struct vm_area_struct *gate_vma) { if (gate_vma && (vma == gate_vma)) return NULL; vma = vma_next(vmi); if (vma) return vma; return gate_vma; } static void free_vma_snapshot(struct coredump_params *cprm) { if (cprm->vma_meta) { int i; for (i = 0; i < cprm->vma_count; i++) { struct file *file = cprm->vma_meta[i].file; if (file) fput(file); } kvfree(cprm->vma_meta); cprm->vma_meta = NULL; } } /* * Under the mmap_lock, take a snapshot of relevant information about the task's * VMAs. */ static bool dump_vma_snapshot(struct coredump_params *cprm) { struct vm_area_struct *gate_vma, *vma = NULL; struct mm_struct *mm = current->mm; VMA_ITERATOR(vmi, mm, 0); int i = 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 false; cprm->vma_data_size = 0; gate_vma = get_gate_vma(mm); cprm->vma_count = mm->map_count + (gate_vma ? 1 : 0); cprm->vma_meta = kvmalloc_array(cprm->vma_count, sizeof(*cprm->vma_meta), GFP_KERNEL); if (!cprm->vma_meta) { mmap_write_unlock(mm); return false; } while ((vma = coredump_next_vma(&vmi, vma, gate_vma)) != NULL) { struct core_vma_metadata *m = cprm->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); m->pgoff = vma->vm_pgoff; m->file = vma->vm_file; if (m->file) get_file(m->file); i++; } mmap_write_unlock(mm); for (i = 0; i < cprm->vma_count; i++) { struct core_vma_metadata *m = cprm->vma_meta + i; if (m->dump_size == DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER) { char elfmag[SELFMAG]; if (copy_from_user(elfmag, (void __user *)m->start, SELFMAG) || memcmp(elfmag, ELFMAG, SELFMAG) != 0) { m->dump_size = 0; } else { m->dump_size = PAGE_SIZE; } } cprm->vma_data_size += m->dump_size; } return true; }