diff options
Diffstat (limited to 'kernel/fs/exec.c')
| -rw-r--r-- | kernel/fs/exec.c | 1747 |
1 files changed, 1747 insertions, 0 deletions
diff --git a/kernel/fs/exec.c b/kernel/fs/exec.c new file mode 100644 index 000000000..0e7125be0 --- /dev/null +++ b/kernel/fs/exec.c @@ -0,0 +1,1747 @@ +/* + * linux/fs/exec.c + * + * Copyright (C) 1991, 1992 Linus Torvalds + */ + +/* + * #!-checking implemented by tytso. + */ +/* + * Demand-loading implemented 01.12.91 - no need to read anything but + * the header into memory. The inode of the executable is put into + * "current->executable", and page faults do the actual loading. Clean. + * + * Once more I can proudly say that linux stood up to being changed: it + * was less than 2 hours work to get demand-loading completely implemented. + * + * Demand loading changed July 1993 by Eric Youngdale. Use mmap instead, + * current->executable is only used by the procfs. This allows a dispatch + * table to check for several different types of binary formats. We keep + * trying until we recognize the file or we run out of supported binary + * formats. + */ + +#include <linux/slab.h> +#include <linux/file.h> +#include <linux/fdtable.h> +#include <linux/mm.h> +#include <linux/vmacache.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 <trace/events/task.h> +#include "internal.h" + +#include <trace/events/sched.h> + +int suid_dumpable = 0; + +static LIST_HEAD(formats); +static DEFINE_RWLOCK(binfmt_lock); + +void __register_binfmt(struct linux_binfmt * fmt, int insert) +{ + BUG_ON(!fmt); + if (WARN_ON(!fmt->load_binary)) + return; + write_lock(&binfmt_lock); + insert ? list_add(&fmt->lh, &formats) : + list_add_tail(&fmt->lh, &formats); + write_unlock(&binfmt_lock); +} + +EXPORT_SYMBOL(__register_binfmt); + +void unregister_binfmt(struct linux_binfmt * fmt) +{ + write_lock(&binfmt_lock); + list_del(&fmt->lh); + write_unlock(&binfmt_lock); +} + +EXPORT_SYMBOL(unregister_binfmt); + +static inline void put_binfmt(struct linux_binfmt * fmt) +{ + module_put(fmt->module); +} + +#ifdef CONFIG_USELIB +/* + * Note that a shared library must be both readable and executable due to + * security reasons. + * + * Also note that we take the address to load from from the file itself. + */ +SYSCALL_DEFINE1(uselib, const char __user *, library) +{ + struct linux_binfmt *fmt; + struct file *file; + struct filename *tmp = getname(library); + int error = PTR_ERR(tmp); + static const struct open_flags uselib_flags = { + .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC, + .acc_mode = MAY_READ | MAY_EXEC | MAY_OPEN, + .intent = LOOKUP_OPEN, + .lookup_flags = LOOKUP_FOLLOW, + }; + + if (IS_ERR(tmp)) + goto out; + + file = do_filp_open(AT_FDCWD, tmp, &uselib_flags); + putname(tmp); + error = PTR_ERR(file); + if (IS_ERR(file)) + goto out; + + error = -EINVAL; + if (!S_ISREG(file_inode(file)->i_mode)) + goto exit; + + error = -EACCES; + if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) + goto exit; + + fsnotify_open(file); + + error = -ENOEXEC; + + read_lock(&binfmt_lock); + list_for_each_entry(fmt, &formats, lh) { + if (!fmt->load_shlib) + continue; + if (!try_module_get(fmt->module)) + continue; + read_unlock(&binfmt_lock); + error = fmt->load_shlib(file); + read_lock(&binfmt_lock); + put_binfmt(fmt); + if (error != -ENOEXEC) + break; + } + read_unlock(&binfmt_lock); +exit: + fput(file); +out: + return error; +} +#endif /* #ifdef CONFIG_USELIB */ + +#ifdef CONFIG_MMU +/* + * The nascent bprm->mm is not visible until exec_mmap() but it can + * use a lot of memory, account these pages in current->mm temporary + * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we + * change the counter back via acct_arg_size(0). + */ +static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages) +{ + struct mm_struct *mm = current->mm; + long diff = (long)(pages - bprm->vma_pages); + + if (!mm || !diff) + return; + + bprm->vma_pages = pages; + add_mm_counter(mm, MM_ANONPAGES, diff); +} + +static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos, + int write) +{ + struct page *page; + int ret; + +#ifdef CONFIG_STACK_GROWSUP + if (write) { + ret = expand_downwards(bprm->vma, pos); + if (ret < 0) + return NULL; + } +#endif + ret = get_user_pages(current, bprm->mm, pos, + 1, write, 1, &page, NULL); + if (ret <= 0) + return NULL; + + if (write) { + unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start; + struct rlimit *rlim; + + acct_arg_size(bprm, size / PAGE_SIZE); + + /* + * We've historically supported up to 32 pages (ARG_MAX) + * of argument strings even with small stacks + */ + if (size <= ARG_MAX) + return page; + + /* + * Limit to 1/4-th the stack size for the argv+env strings. + * This ensures that: + * - the remaining binfmt code will not run out of stack space, + * - the program will have a reasonable amount of stack left + * to work from. + */ + rlim = current->signal->rlim; + if (size > ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur) / 4) { + put_page(page); + return NULL; + } + } + + return page; +} + +static void put_arg_page(struct page *page) +{ + put_page(page); +} + +static void free_arg_page(struct linux_binprm *bprm, int i) +{ +} + +static void free_arg_pages(struct linux_binprm *bprm) +{ +} + +static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos, + struct page *page) +{ + flush_cache_page(bprm->vma, pos, page_to_pfn(page)); +} + +static int __bprm_mm_init(struct linux_binprm *bprm) +{ + int err; + struct vm_area_struct *vma = NULL; + struct mm_struct *mm = bprm->mm; + + bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL); + if (!vma) + return -ENOMEM; + + down_write(&mm->mmap_sem); + vma->vm_mm = mm; + + /* + * Place the stack at the largest stack address the architecture + * supports. Later, we'll move this to an appropriate place. We don't + * use STACK_TOP because that can depend on attributes which aren't + * configured yet. + */ + BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP); + vma->vm_end = STACK_TOP_MAX; + vma->vm_start = vma->vm_end - PAGE_SIZE; + vma->vm_flags = VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP; + vma->vm_page_prot = vm_get_page_prot(vma->vm_flags); + INIT_LIST_HEAD(&vma->anon_vma_chain); + + err = insert_vm_struct(mm, vma); + if (err) + goto err; + + mm->stack_vm = mm->total_vm = 1; + arch_bprm_mm_init(mm, vma); + up_write(&mm->mmap_sem); + bprm->p = vma->vm_end - sizeof(void *); + return 0; +err: + up_write(&mm->mmap_sem); + bprm->vma = NULL; + kmem_cache_free(vm_area_cachep, vma); + return err; +} + +static bool valid_arg_len(struct linux_binprm *bprm, long len) +{ + return len <= MAX_ARG_STRLEN; +} + +#else + +static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages) +{ +} + +static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos, + int write) +{ + struct page *page; + + page = bprm->page[pos / PAGE_SIZE]; + if (!page && write) { + page = alloc_page(GFP_HIGHUSER|__GFP_ZERO); + if (!page) + return NULL; + bprm->page[pos / PAGE_SIZE] = page; + } + + return page; +} + +static void put_arg_page(struct page *page) +{ +} + +static void free_arg_page(struct linux_binprm *bprm, int i) +{ + if (bprm->page[i]) { + __free_page(bprm->page[i]); + bprm->page[i] = NULL; + } +} + +static void free_arg_pages(struct linux_binprm *bprm) +{ + int i; + + for (i = 0; i < MAX_ARG_PAGES; i++) + free_arg_page(bprm, i); +} + +static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos, + struct page *page) +{ +} + +static int __bprm_mm_init(struct linux_binprm *bprm) +{ + bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *); + return 0; +} + +static bool valid_arg_len(struct linux_binprm *bprm, long len) +{ + return len <= bprm->p; +} + +#endif /* CONFIG_MMU */ + +/* + * Create a new mm_struct and populate it with a temporary stack + * vm_area_struct. We don't have enough context at this point to set the stack + * flags, permissions, and offset, so we use temporary values. We'll update + * them later in setup_arg_pages(). + */ +static int bprm_mm_init(struct linux_binprm *bprm) +{ + int err; + struct mm_struct *mm = NULL; + + bprm->mm = mm = mm_alloc(); + err = -ENOMEM; + if (!mm) + goto err; + + err = __bprm_mm_init(bprm); + if (err) + goto err; + + return 0; + +err: + if (mm) { + bprm->mm = NULL; + mmdrop(mm); + } + + return err; +} + +struct user_arg_ptr { +#ifdef CONFIG_COMPAT + bool is_compat; +#endif + union { + const char __user *const __user *native; +#ifdef CONFIG_COMPAT + const compat_uptr_t __user *compat; +#endif + } ptr; +}; + +static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr) +{ + const char __user *native; + +#ifdef CONFIG_COMPAT + if (unlikely(argv.is_compat)) { + compat_uptr_t compat; + + if (get_user(compat, argv.ptr.compat + nr)) + return ERR_PTR(-EFAULT); + + return compat_ptr(compat); + } +#endif + + if (get_user(native, argv.ptr.native + nr)) + return ERR_PTR(-EFAULT); + + return native; +} + +/* + * count() counts the number of strings in array ARGV. + */ +static int count(struct user_arg_ptr argv, int max) +{ + int i = 0; + + if (argv.ptr.native != NULL) { + for (;;) { + const char __user *p = get_user_arg_ptr(argv, i); + + if (!p) + break; + + if (IS_ERR(p)) + return -EFAULT; + + if (i >= max) + return -E2BIG; + ++i; + + if (fatal_signal_pending(current)) + return -ERESTARTNOHAND; + cond_resched(); + } + } + return i; +} + +/* + * 'copy_strings()' copies argument/environment strings from the old + * processes's memory to the new process's stack. The call to get_user_pages() + * ensures the destination page is created and not swapped out. + */ +static int copy_strings(int argc, struct user_arg_ptr argv, + struct linux_binprm *bprm) +{ + struct page *kmapped_page = NULL; + char *kaddr = NULL; + unsigned long kpos = 0; + int ret; + + while (argc-- > 0) { + const char __user *str; + int len; + unsigned long pos; + + ret = -EFAULT; + str = get_user_arg_ptr(argv, argc); + if (IS_ERR(str)) + goto out; + + len = strnlen_user(str, MAX_ARG_STRLEN); + if (!len) + goto out; + + ret = -E2BIG; + if (!valid_arg_len(bprm, len)) + goto out; + + /* We're going to work our way backwords. */ + pos = bprm->p; + str += len; + bprm->p -= len; + + while (len > 0) { + int offset, bytes_to_copy; + + if (fatal_signal_pending(current)) { + ret = -ERESTARTNOHAND; + goto out; + } + cond_resched(); + + offset = pos % PAGE_SIZE; + if (offset == 0) + offset = PAGE_SIZE; + + bytes_to_copy = offset; + if (bytes_to_copy > len) + bytes_to_copy = len; + + offset -= bytes_to_copy; + pos -= bytes_to_copy; + str -= bytes_to_copy; + len -= bytes_to_copy; + + if (!kmapped_page || kpos != (pos & PAGE_MASK)) { + struct page *page; + + page = get_arg_page(bprm, pos, 1); + if (!page) { + ret = -E2BIG; + goto out; + } + + if (kmapped_page) { + flush_kernel_dcache_page(kmapped_page); + kunmap(kmapped_page); + put_arg_page(kmapped_page); + } + kmapped_page = page; + kaddr = kmap(kmapped_page); + kpos = pos & PAGE_MASK; + flush_arg_page(bprm, kpos, kmapped_page); + } + if (copy_from_user(kaddr+offset, str, bytes_to_copy)) { + ret = -EFAULT; + goto out; + } + } + } + ret = 0; +out: + if (kmapped_page) { + flush_kernel_dcache_page(kmapped_page); + kunmap(kmapped_page); + put_arg_page(kmapped_page); + } + return ret; +} + +/* + * Like copy_strings, but get argv and its values from kernel memory. + */ +int copy_strings_kernel(int argc, const char *const *__argv, + struct linux_binprm *bprm) +{ + int r; + mm_segment_t oldfs = get_fs(); + struct user_arg_ptr argv = { + .ptr.native = (const char __user *const __user *)__argv, + }; + + set_fs(KERNEL_DS); + r = copy_strings(argc, argv, bprm); + set_fs(oldfs); + + return r; +} +EXPORT_SYMBOL(copy_strings_kernel); + +#ifdef CONFIG_MMU + +/* + * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX. Once + * the binfmt code determines where the new stack should reside, we shift it to + * its final location. The process proceeds as follows: + * + * 1) Use shift to calculate the new vma endpoints. + * 2) Extend vma to cover both the old and new ranges. This ensures the + * arguments passed to subsequent functions are consistent. + * 3) Move vma's page tables to the new range. + * 4) Free up any cleared pgd range. + * 5) Shrink the vma to cover only the new range. + */ +static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift) +{ + struct mm_struct *mm = vma->vm_mm; + unsigned long old_start = vma->vm_start; + unsigned long old_end = vma->vm_end; + unsigned long length = old_end - old_start; + unsigned long new_start = old_start - shift; + unsigned long new_end = old_end - shift; + struct mmu_gather tlb; + + BUG_ON(new_start > new_end); + + /* + * ensure there are no vmas between where we want to go + * and where we are + */ + if (vma != find_vma(mm, new_start)) + return -EFAULT; + + /* + * cover the whole range: [new_start, old_end) + */ + if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL)) + return -ENOMEM; + + /* + * move the page tables downwards, on failure we rely on + * process cleanup to remove whatever mess we made. + */ + if (length != move_page_tables(vma, old_start, + vma, new_start, length, false)) + return -ENOMEM; + + lru_add_drain(); + tlb_gather_mmu(&tlb, mm, old_start, old_end); + if (new_end > old_start) { + /* + * when the old and new regions overlap clear from new_end. + */ + free_pgd_range(&tlb, new_end, old_end, new_end, + vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING); + } else { + /* + * otherwise, clean from old_start; this is done to not touch + * the address space in [new_end, old_start) some architectures + * have constraints on va-space that make this illegal (IA64) - + * for the others its just a little faster. + */ + free_pgd_range(&tlb, old_start, old_end, new_end, + vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING); + } + tlb_finish_mmu(&tlb, old_start, old_end); + + /* + * Shrink the vma to just the new range. Always succeeds. + */ + vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL); + + return 0; +} + +/* + * Finalizes the stack vm_area_struct. The flags and permissions are updated, + * the stack is optionally relocated, and some extra space is added. + */ +int setup_arg_pages(struct linux_binprm *bprm, + unsigned long stack_top, + int executable_stack) +{ + unsigned long ret; + unsigned long stack_shift; + struct mm_struct *mm = current->mm; + struct vm_area_struct *vma = bprm->vma; + struct vm_area_struct *prev = NULL; + unsigned long vm_flags; + unsigned long stack_base; + unsigned long stack_size; + unsigned long stack_expand; + unsigned long rlim_stack; + +#ifdef CONFIG_STACK_GROWSUP + /* Limit stack size */ + stack_base = rlimit_max(RLIMIT_STACK); + if (stack_base > STACK_SIZE_MAX) + stack_base = STACK_SIZE_MAX; + + /* Add space for stack randomization. */ + stack_base += (STACK_RND_MASK << PAGE_SHIFT); + + /* Make sure we didn't let the argument array grow too large. */ + if (vma->vm_end - vma->vm_start > stack_base) + return -ENOMEM; + + stack_base = PAGE_ALIGN(stack_top - stack_base); + + stack_shift = vma->vm_start - stack_base; + mm->arg_start = bprm->p - stack_shift; + bprm->p = vma->vm_end - stack_shift; +#else + stack_top = arch_align_stack(stack_top); + stack_top = PAGE_ALIGN(stack_top); + + if (unlikely(stack_top < mmap_min_addr) || + unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr)) + return -ENOMEM; + + stack_shift = vma->vm_end - stack_top; + + bprm->p -= stack_shift; + mm->arg_start = bprm->p; +#endif + + if (bprm->loader) + bprm->loader -= stack_shift; + bprm->exec -= stack_shift; + + down_write(&mm->mmap_sem); + vm_flags = VM_STACK_FLAGS; + + /* + * Adjust stack execute permissions; explicitly enable for + * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone + * (arch default) otherwise. + */ + if (unlikely(executable_stack == EXSTACK_ENABLE_X)) + vm_flags |= VM_EXEC; + else if (executable_stack == EXSTACK_DISABLE_X) + vm_flags &= ~VM_EXEC; + vm_flags |= mm->def_flags; + vm_flags |= VM_STACK_INCOMPLETE_SETUP; + + ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end, + vm_flags); + if (ret) + goto out_unlock; + BUG_ON(prev != vma); + + /* Move stack pages down in memory. */ + if (stack_shift) { + ret = shift_arg_pages(vma, stack_shift); + if (ret) + goto out_unlock; + } + + /* mprotect_fixup is overkill to remove the temporary stack flags */ + vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP; + + stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */ + stack_size = vma->vm_end - vma->vm_start; + /* + * Align this down to a page boundary as expand_stack + * will align it up. + */ + rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK; +#ifdef CONFIG_STACK_GROWSUP + if (stack_size + stack_expand > rlim_stack) + stack_base = vma->vm_start + rlim_stack; + else + stack_base = vma->vm_end + stack_expand; +#else + if (stack_size + stack_expand > rlim_stack) + stack_base = vma->vm_end - rlim_stack; + else + stack_base = vma->vm_start - stack_expand; +#endif + current->mm->start_stack = bprm->p; + ret = expand_stack(vma, stack_base); + if (ret) + ret = -EFAULT; + +out_unlock: + up_write(&mm->mmap_sem); + return ret; +} +EXPORT_SYMBOL(setup_arg_pages); + +#endif /* CONFIG_MMU */ + +static struct file *do_open_execat(int fd, struct filename *name, int flags) +{ + struct file *file; + int err; + struct open_flags open_exec_flags = { + .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC, + .acc_mode = MAY_EXEC | MAY_OPEN, + .intent = LOOKUP_OPEN, + .lookup_flags = LOOKUP_FOLLOW, + }; + + if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0) + return ERR_PTR(-EINVAL); + if (flags & AT_SYMLINK_NOFOLLOW) + open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW; + if (flags & AT_EMPTY_PATH) + open_exec_flags.lookup_flags |= LOOKUP_EMPTY; + + file = do_filp_open(fd, name, &open_exec_flags); + if (IS_ERR(file)) + goto out; + + err = -EACCES; + if (!S_ISREG(file_inode(file)->i_mode)) + goto exit; + + if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) + goto exit; + + err = deny_write_access(file); + if (err) + goto exit; + + if (name->name[0] != '\0') + fsnotify_open(file); + +out: + return file; + +exit: + fput(file); + return ERR_PTR(err); +} + +struct file *open_exec(const char *name) +{ + struct filename *filename = getname_kernel(name); + struct file *f = ERR_CAST(filename); + + if (!IS_ERR(filename)) { + f = do_open_execat(AT_FDCWD, filename, 0); + putname(filename); + } + return f; +} +EXPORT_SYMBOL(open_exec); + +int kernel_read(struct file *file, loff_t offset, + char *addr, unsigned long count) +{ + mm_segment_t old_fs; + loff_t pos = offset; + int result; + + old_fs = get_fs(); + set_fs(get_ds()); + /* The cast to a user pointer is valid due to the set_fs() */ + result = vfs_read(file, (void __user *)addr, count, &pos); + set_fs(old_fs); + return result; +} + +EXPORT_SYMBOL(kernel_read); + +ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len) +{ + ssize_t res = vfs_read(file, (void __user *)addr, len, &pos); + if (res > 0) + flush_icache_range(addr, addr + len); + return res; +} +EXPORT_SYMBOL(read_code); + +static int exec_mmap(struct mm_struct *mm) +{ + struct task_struct *tsk; + struct mm_struct *old_mm, *active_mm; + + /* Notify parent that we're no longer interested in the old VM */ + tsk = current; + old_mm = current->mm; + mm_release(tsk, old_mm); + + if (old_mm) { + sync_mm_rss(old_mm); + /* + * Make sure that if there is a core dump in progress + * for the old mm, we get out and die instead of going + * through with the exec. We must hold mmap_sem around + * checking core_state and changing tsk->mm. + */ + down_read(&old_mm->mmap_sem); + if (unlikely(old_mm->core_state)) { + up_read(&old_mm->mmap_sem); + return -EINTR; + } + } + task_lock(tsk); + preempt_disable_rt(); + active_mm = tsk->active_mm; + tsk->mm = mm; + tsk->active_mm = mm; + activate_mm(active_mm, mm); + tsk->mm->vmacache_seqnum = 0; + vmacache_flush(tsk); + preempt_enable_rt(); + task_unlock(tsk); + if (old_mm) { + up_read(&old_mm->mmap_sem); + BUG_ON(active_mm != old_mm); + setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm); + mm_update_next_owner(old_mm); + mmput(old_mm); + return 0; + } + mmdrop(active_mm); + return 0; +} + +/* + * This function makes sure the current process has its own signal table, + * so that flush_signal_handlers can later reset the handlers without + * disturbing other processes. (Other processes might share the signal + * table via the CLONE_SIGHAND option to clone().) + */ +static int de_thread(struct task_struct *tsk) +{ + struct signal_struct *sig = tsk->signal; + struct sighand_struct *oldsighand = tsk->sighand; + spinlock_t *lock = &oldsighand->siglock; + + if (thread_group_empty(tsk)) + goto no_thread_group; + + /* + * Kill all other threads in the thread group. + */ + spin_lock_irq(lock); + if (signal_group_exit(sig)) { + /* + * Another group action in progress, just + * return so that the signal is processed. + */ + spin_unlock_irq(lock); + return -EAGAIN; + } + + sig->group_exit_task = tsk; + sig->notify_count = zap_other_threads(tsk); + if (!thread_group_leader(tsk)) + sig->notify_count--; + + while (sig->notify_count) { + __set_current_state(TASK_KILLABLE); + spin_unlock_irq(lock); + schedule(); + if (unlikely(__fatal_signal_pending(tsk))) + goto killed; + spin_lock_irq(lock); + } + spin_unlock_irq(lock); + + /* + * At this point all other threads have exited, all we have to + * do is to wait for the thread group leader to become inactive, + * and to assume its PID: + */ + if (!thread_group_leader(tsk)) { + struct task_struct *leader = tsk->group_leader; + + for (;;) { + threadgroup_change_begin(tsk); + write_lock_irq(&tasklist_lock); + /* + * Do this under tasklist_lock to ensure that + * exit_notify() can't miss ->group_exit_task + */ + sig->notify_count = -1; + if (likely(leader->exit_state)) + break; + __set_current_state(TASK_KILLABLE); + write_unlock_irq(&tasklist_lock); + threadgroup_change_end(tsk); + schedule(); + if (unlikely(__fatal_signal_pending(tsk))) + goto killed; + } + + /* + * The only record we have of the real-time age of a + * process, regardless of execs it's done, is start_time. + * All the past CPU time is accumulated in signal_struct + * from sister threads now dead. But in this non-leader + * exec, nothing survives from the original leader thread, + * whose birth marks the true age of this process now. + * When we take on its identity by switching to its PID, we + * also take its birthdate (always earlier than our own). + */ + tsk->start_time = leader->start_time; + tsk->real_start_time = leader->real_start_time; + + BUG_ON(!same_thread_group(leader, tsk)); + BUG_ON(has_group_leader_pid(tsk)); + /* + * An exec() starts a new thread group with the + * TGID of the previous thread group. Rehash the + * two threads with a switched PID, and release + * the former thread group leader: + */ + + /* Become a process group leader with the old leader's pid. + * The old leader becomes a thread of the this thread group. + * Note: The old leader also uses this pid until release_task + * is called. Odd but simple and correct. + */ + tsk->pid = leader->pid; + change_pid(tsk, PIDTYPE_PID, task_pid(leader)); + transfer_pid(leader, tsk, PIDTYPE_PGID); + transfer_pid(leader, tsk, PIDTYPE_SID); + + list_replace_rcu(&leader->tasks, &tsk->tasks); + list_replace_init(&leader->sibling, &tsk->sibling); + + tsk->group_leader = tsk; + leader->group_leader = tsk; + + tsk->exit_signal = SIGCHLD; + leader->exit_signal = -1; + + BUG_ON(leader->exit_state != EXIT_ZOMBIE); + leader->exit_state = EXIT_DEAD; + + /* + * We are going to release_task()->ptrace_unlink() silently, + * the tracer can sleep in do_wait(). EXIT_DEAD guarantees + * the tracer wont't block again waiting for this thread. + */ + if (unlikely(leader->ptrace)) + __wake_up_parent(leader, leader->parent); + write_unlock_irq(&tasklist_lock); + threadgroup_change_end(tsk); + + release_task(leader); + } + + sig->group_exit_task = NULL; + sig->notify_count = 0; + +no_thread_group: + /* we have changed execution domain */ + tsk->exit_signal = SIGCHLD; + + exit_itimers(sig); + flush_itimer_signals(); + + if (atomic_read(&oldsighand->count) != 1) { + struct sighand_struct *newsighand; + /* + * This ->sighand is shared with the CLONE_SIGHAND + * but not CLONE_THREAD task, switch to the new one. + */ + newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); + if (!newsighand) + return -ENOMEM; + + atomic_set(&newsighand->count, 1); + memcpy(newsighand->action, oldsighand->action, + sizeof(newsighand->action)); + + write_lock_irq(&tasklist_lock); + spin_lock(&oldsighand->siglock); + rcu_assign_pointer(tsk->sighand, newsighand); + spin_unlock(&oldsighand->siglock); + write_unlock_irq(&tasklist_lock); + + __cleanup_sighand(oldsighand); + } + + BUG_ON(!thread_group_leader(tsk)); + return 0; + +killed: + /* protects against exit_notify() and __exit_signal() */ + read_lock(&tasklist_lock); + sig->group_exit_task = NULL; + sig->notify_count = 0; + read_unlock(&tasklist_lock); + return -EAGAIN; +} + +char *get_task_comm(char *buf, struct task_struct *tsk) +{ + /* buf must be at least sizeof(tsk->comm) in size */ + task_lock(tsk); + strncpy(buf, tsk->comm, sizeof(tsk->comm)); + task_unlock(tsk); + return buf; +} +EXPORT_SYMBOL_GPL(get_task_comm); + +/* + * These functions flushes out all traces of the currently running executable + * so that a new one can be started + */ + +void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec) +{ + task_lock(tsk); + trace_task_rename(tsk, buf); + strlcpy(tsk->comm, buf, sizeof(tsk->comm)); + task_unlock(tsk); + perf_event_comm(tsk, exec); +} + +int flush_old_exec(struct linux_binprm * bprm) +{ + int retval; + + /* + * Make sure we have a private signal table and that + * we are unassociated from the previous thread group. + */ + retval = de_thread(current); + if (retval) + goto out; + + /* + * Must be called _before_ exec_mmap() as bprm->mm is + * not visibile until then. This also enables the update + * to be lockless. + */ + set_mm_exe_file(bprm->mm, bprm->file); + + /* + * Release all of the old mmap stuff + */ + acct_arg_size(bprm, 0); + retval = exec_mmap(bprm->mm); + if (retval) + goto out; + + bprm->mm = NULL; /* We're using it now */ + + set_fs(USER_DS); + current->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD | + PF_NOFREEZE | PF_NO_SETAFFINITY); + flush_thread(); + current->personality &= ~bprm->per_clear; + + return 0; + +out: + return retval; +} +EXPORT_SYMBOL(flush_old_exec); + +void would_dump(struct linux_binprm *bprm, struct file *file) +{ + if (inode_permission(file_inode(file), MAY_READ) < 0) + bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP; +} +EXPORT_SYMBOL(would_dump); + +void setup_new_exec(struct linux_binprm * bprm) +{ + arch_pick_mmap_layout(current->mm); + + /* This is the point of no return */ + current->sas_ss_sp = current->sas_ss_size = 0; + + if (uid_eq(current_euid(), current_uid()) && gid_eq(current_egid(), current_gid())) + set_dumpable(current->mm, SUID_DUMP_USER); + else + set_dumpable(current->mm, suid_dumpable); + + perf_event_exec(); + __set_task_comm(current, kbasename(bprm->filename), true); + + /* Set the new mm task size. We have to do that late because it may + * depend on TIF_32BIT which is only updated in flush_thread() on + * some architectures like powerpc + */ + current->mm->task_size = TASK_SIZE; + + /* install the new credentials */ + if (!uid_eq(bprm->cred->uid, current_euid()) || + !gid_eq(bprm->cred->gid, current_egid())) { + current->pdeath_signal = 0; + } else { + would_dump(bprm, bprm->file); + if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP) + set_dumpable(current->mm, suid_dumpable); + } + + /* An exec changes our domain. We are no longer part of the thread + group */ + current->self_exec_id++; + flush_signal_handlers(current, 0); + do_close_on_exec(current->files); +} +EXPORT_SYMBOL(setup_new_exec); + +/* + * Prepare credentials and lock ->cred_guard_mutex. + * install_exec_creds() commits the new creds and drops the lock. + * Or, if exec fails before, free_bprm() should release ->cred and + * and unlock. + */ +int prepare_bprm_creds(struct linux_binprm *bprm) +{ + if (mutex_lock_interruptible(¤t->signal->cred_guard_mutex)) + return -ERESTARTNOINTR; + + bprm->cred = prepare_exec_creds(); + if (likely(bprm->cred)) + return 0; + + mutex_unlock(¤t->signal->cred_guard_mutex); + return -ENOMEM; +} + +static void free_bprm(struct linux_binprm *bprm) +{ + free_arg_pages(bprm); + if (bprm->cred) { + mutex_unlock(¤t->signal->cred_guard_mutex); + abort_creds(bprm->cred); + } + if (bprm->file) { + allow_write_access(bprm->file); + fput(bprm->file); + } + /* If a binfmt changed the interp, free it. */ + if (bprm->interp != bprm->filename) + kfree(bprm->interp); + kfree(bprm); +} + +int bprm_change_interp(char *interp, struct linux_binprm *bprm) +{ + /* If a binfmt changed the interp, free it first. */ + if (bprm->interp != bprm->filename) + kfree(bprm->interp); + bprm->interp = kstrdup(interp, GFP_KERNEL); + if (!bprm->interp) + return -ENOMEM; + return 0; +} +EXPORT_SYMBOL(bprm_change_interp); + +/* + * install the new credentials for this executable + */ +void install_exec_creds(struct linux_binprm *bprm) +{ + security_bprm_committing_creds(bprm); + + commit_creds(bprm->cred); + bprm->cred = NULL; + + /* + * Disable monitoring for regular users + * when executing setuid binaries. Must + * wait until new credentials are committed + * by commit_creds() above + */ + if (get_dumpable(current->mm) != SUID_DUMP_USER) + perf_event_exit_task(current); + /* + * cred_guard_mutex must be held at least to this point to prevent + * ptrace_attach() from altering our determination of the task's + * credentials; any time after this it may be unlocked. + */ + security_bprm_committed_creds(bprm); + mutex_unlock(¤t->signal->cred_guard_mutex); +} +EXPORT_SYMBOL(install_exec_creds); + +/* + * determine how safe it is to execute the proposed program + * - the caller must hold ->cred_guard_mutex to protect against + * PTRACE_ATTACH or seccomp thread-sync + */ +static void check_unsafe_exec(struct linux_binprm *bprm) +{ + struct task_struct *p = current, *t; + unsigned n_fs; + + if (p->ptrace) { + if (p->ptrace & PT_PTRACE_CAP) + bprm->unsafe |= LSM_UNSAFE_PTRACE_CAP; + else + bprm->unsafe |= LSM_UNSAFE_PTRACE; + } + + /* + * This isn't strictly necessary, but it makes it harder for LSMs to + * mess up. + */ + if (task_no_new_privs(current)) + bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS; + + t = p; + n_fs = 1; + spin_lock(&p->fs->lock); + rcu_read_lock(); + while_each_thread(p, t) { + if (t->fs == p->fs) + n_fs++; + } + rcu_read_unlock(); + + if (p->fs->users > n_fs) + bprm->unsafe |= LSM_UNSAFE_SHARE; + else + p->fs->in_exec = 1; + spin_unlock(&p->fs->lock); +} + +static void bprm_fill_uid(struct linux_binprm *bprm) +{ + struct inode *inode; + unsigned int mode; + kuid_t uid; + kgid_t gid; + + /* clear any previous set[ug]id data from a previous binary */ + bprm->cred->euid = current_euid(); + bprm->cred->egid = current_egid(); + + if (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID) + return; + + if (task_no_new_privs(current)) + return; + + inode = file_inode(bprm->file); + mode = READ_ONCE(inode->i_mode); + if (!(mode & (S_ISUID|S_ISGID))) + return; + + /* Be careful if suid/sgid is set */ + mutex_lock(&inode->i_mutex); + + /* reload atomically mode/uid/gid now that lock held */ + mode = inode->i_mode; + uid = inode->i_uid; + gid = inode->i_gid; + mutex_unlock(&inode->i_mutex); + + /* We ignore suid/sgid if there are no mappings for them in the ns */ + if (!kuid_has_mapping(bprm->cred->user_ns, uid) || + !kgid_has_mapping(bprm->cred->user_ns, gid)) + return; + + if (mode & S_ISUID) { + bprm->per_clear |= PER_CLEAR_ON_SETID; + bprm->cred->euid = uid; + } + + if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { + bprm->per_clear |= PER_CLEAR_ON_SETID; + bprm->cred->egid = gid; + } +} + +/* + * Fill the binprm structure from the inode. + * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes + * + * This may be called multiple times for binary chains (scripts for example). + */ +int prepare_binprm(struct linux_binprm *bprm) +{ + int retval; + + bprm_fill_uid(bprm); + + /* fill in binprm security blob */ + retval = security_bprm_set_creds(bprm); + if (retval) + return retval; + bprm->cred_prepared = 1; + + memset(bprm->buf, 0, BINPRM_BUF_SIZE); + return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE); +} + +EXPORT_SYMBOL(prepare_binprm); + +/* + * Arguments are '\0' separated strings found at the location bprm->p + * points to; chop off the first by relocating brpm->p to right after + * the first '\0' encountered. + */ +int remove_arg_zero(struct linux_binprm *bprm) +{ + int ret = 0; + unsigned long offset; + char *kaddr; + struct page *page; + + if (!bprm->argc) + return 0; + + do { + offset = bprm->p & ~PAGE_MASK; + page = get_arg_page(bprm, bprm->p, 0); + if (!page) { + ret = -EFAULT; + goto out; + } + kaddr = kmap_atomic(page); + + for (; offset < PAGE_SIZE && kaddr[offset]; + offset++, bprm->p++) + ; + + kunmap_atomic(kaddr); + put_arg_page(page); + + if (offset == PAGE_SIZE) + free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1); + } while (offset == PAGE_SIZE); + + bprm->p++; + bprm->argc--; + ret = 0; + +out: + return ret; +} +EXPORT_SYMBOL(remove_arg_zero); + +#define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e)) +/* + * cycle the list of binary formats handler, until one recognizes the image + */ +int search_binary_handler(struct linux_binprm *bprm) +{ + bool need_retry = IS_ENABLED(CONFIG_MODULES); + struct linux_binfmt *fmt; + int retval; + + /* This allows 4 levels of binfmt rewrites before failing hard. */ + if (bprm->recursion_depth > 5) + return -ELOOP; + + retval = security_bprm_check(bprm); + if (retval) + return retval; + + retval = -ENOENT; + retry: + read_lock(&binfmt_lock); + list_for_each_entry(fmt, &formats, lh) { + if (!try_module_get(fmt->module)) + continue; + read_unlock(&binfmt_lock); + bprm->recursion_depth++; + retval = fmt->load_binary(bprm); + read_lock(&binfmt_lock); + put_binfmt(fmt); + bprm->recursion_depth--; + if (retval < 0 && !bprm->mm) { + /* we got to flush_old_exec() and failed after it */ + read_unlock(&binfmt_lock); + force_sigsegv(SIGSEGV, current); + return retval; + } + if (retval != -ENOEXEC || !bprm->file) { + read_unlock(&binfmt_lock); + return retval; + } + } + read_unlock(&binfmt_lock); + + if (need_retry) { + if (printable(bprm->buf[0]) && printable(bprm->buf[1]) && + printable(bprm->buf[2]) && printable(bprm->buf[3])) + return retval; + if (request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2)) < 0) + return retval; + need_retry = false; + goto retry; + } + + return retval; +} +EXPORT_SYMBOL(search_binary_handler); + +static int exec_binprm(struct linux_binprm *bprm) +{ + pid_t old_pid, old_vpid; + int ret; + + /* Need to fetch pid before load_binary changes it */ + old_pid = current->pid; + rcu_read_lock(); + old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent)); + rcu_read_unlock(); + + ret = search_binary_handler(bprm); + if (ret >= 0) { + audit_bprm(bprm); + trace_sched_process_exec(current, old_pid, bprm); + ptrace_event(PTRACE_EVENT_EXEC, old_vpid); + proc_exec_connector(current); + } + + return ret; +} + +/* + * sys_execve() executes a new program. + */ +static int do_execveat_common(int fd, struct filename *filename, + struct user_arg_ptr argv, + struct user_arg_ptr envp, + int flags) +{ + char *pathbuf = NULL; + struct linux_binprm *bprm; + struct file *file; + struct files_struct *displaced; + int retval; + + if (IS_ERR(filename)) + return PTR_ERR(filename); + + /* + * We move the actual failure in case of RLIMIT_NPROC excess from + * set*uid() to execve() because too many poorly written programs + * don't check setuid() return code. Here we additionally recheck + * whether NPROC limit is still exceeded. + */ + if ((current->flags & PF_NPROC_EXCEEDED) && + atomic_read(¤t_user()->processes) > rlimit(RLIMIT_NPROC)) { + retval = -EAGAIN; + goto out_ret; + } + + /* We're below the limit (still or again), so we don't want to make + * further execve() calls fail. */ + current->flags &= ~PF_NPROC_EXCEEDED; + + retval = unshare_files(&displaced); + if (retval) + goto out_ret; + + retval = -ENOMEM; + bprm = kzalloc(sizeof(*bprm), GFP_KERNEL); + if (!bprm) + goto out_files; + + retval = prepare_bprm_creds(bprm); + if (retval) + goto out_free; + + check_unsafe_exec(bprm); + current->in_execve = 1; + + file = do_open_execat(fd, filename, flags); + retval = PTR_ERR(file); + if (IS_ERR(file)) + goto out_unmark; + + sched_exec(); + + bprm->file = file; + if (fd == AT_FDCWD || filename->name[0] == '/') { + bprm->filename = filename->name; + } else { + if (filename->name[0] == '\0') + pathbuf = kasprintf(GFP_TEMPORARY, "/dev/fd/%d", fd); + else + pathbuf = kasprintf(GFP_TEMPORARY, "/dev/fd/%d/%s", + fd, filename->name); + if (!pathbuf) { + retval = -ENOMEM; + goto out_unmark; + } + /* + * Record that a name derived from an O_CLOEXEC fd will be + * inaccessible after exec. Relies on having exclusive access to + * current->files (due to unshare_files above). + */ + if (close_on_exec(fd, rcu_dereference_raw(current->files->fdt))) + bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE; + bprm->filename = pathbuf; + } + bprm->interp = bprm->filename; + + retval = bprm_mm_init(bprm); + if (retval) + goto out_unmark; + + bprm->argc = count(argv, MAX_ARG_STRINGS); + if ((retval = bprm->argc) < 0) + goto out; + + bprm->envc = count(envp, MAX_ARG_STRINGS); + if ((retval = bprm->envc) < 0) + goto out; + + retval = prepare_binprm(bprm); + if (retval < 0) + goto out; + + retval = copy_strings_kernel(1, &bprm->filename, bprm); + if (retval < 0) + goto out; + + bprm->exec = bprm->p; + retval = copy_strings(bprm->envc, envp, bprm); + if (retval < 0) + goto out; + + retval = copy_strings(bprm->argc, argv, bprm); + if (retval < 0) + goto out; + + retval = exec_binprm(bprm); + if (retval < 0) + goto out; + + /* execve succeeded */ + current->fs->in_exec = 0; + current->in_execve = 0; + acct_update_integrals(current); + task_numa_free(current); + free_bprm(bprm); + kfree(pathbuf); + putname(filename); + if (displaced) + put_files_struct(displaced); + return retval; + +out: + if (bprm->mm) { + acct_arg_size(bprm, 0); + mmput(bprm->mm); + } + +out_unmark: + current->fs->in_exec = 0; + current->in_execve = 0; + +out_free: + free_bprm(bprm); + kfree(pathbuf); + +out_files: + if (displaced) + reset_files_struct(displaced); +out_ret: + putname(filename); + return retval; +} + +int do_execve(struct filename *filename, + const char __user *const __user *__argv, + const char __user *const __user *__envp) +{ + struct user_arg_ptr argv = { .ptr.native = __argv }; + struct user_arg_ptr envp = { .ptr.native = __envp }; + return do_execveat_common(AT_FDCWD, filename, argv, envp, 0); +} + +int do_execveat(int fd, struct filename *filename, + const char __user *const __user *__argv, + const char __user *const __user *__envp, + int flags) +{ + struct user_arg_ptr argv = { .ptr.native = __argv }; + struct user_arg_ptr envp = { .ptr.native = __envp }; + + return do_execveat_common(fd, filename, argv, envp, flags); +} + +#ifdef CONFIG_COMPAT +static int compat_do_execve(struct filename *filename, + const compat_uptr_t __user *__argv, + const compat_uptr_t __user *__envp) +{ + struct user_arg_ptr argv = { + .is_compat = true, + .ptr.compat = __argv, + }; + struct user_arg_ptr envp = { + .is_compat = true, + .ptr.compat = __envp, + }; + return do_execveat_common(AT_FDCWD, filename, argv, envp, 0); +} + +static int compat_do_execveat(int fd, struct filename *filename, + const compat_uptr_t __user *__argv, + const compat_uptr_t __user *__envp, + int flags) +{ + struct user_arg_ptr argv = { + .is_compat = true, + .ptr.compat = __argv, + }; + struct user_arg_ptr envp = { + .is_compat = true, + .ptr.compat = __envp, + }; + return do_execveat_common(fd, filename, argv, envp, flags); +} +#endif + +void set_binfmt(struct linux_binfmt *new) +{ + struct mm_struct *mm = current->mm; + + if (mm->binfmt) + module_put(mm->binfmt->module); + + mm->binfmt = new; + if (new) + __module_get(new->module); +} +EXPORT_SYMBOL(set_binfmt); + +/* + * set_dumpable stores three-value SUID_DUMP_* into mm->flags. + */ +void set_dumpable(struct mm_struct *mm, int value) +{ + unsigned long old, new; + + if (WARN_ON((unsigned)value > SUID_DUMP_ROOT)) + return; + + do { + old = ACCESS_ONCE(mm->flags); + new = (old & ~MMF_DUMPABLE_MASK) | value; + } while (cmpxchg(&mm->flags, old, new) != old); +} + +SYSCALL_DEFINE3(execve, + const char __user *, filename, + const char __user *const __user *, argv, + const char __user *const __user *, envp) +{ + return do_execve(getname(filename), argv, envp); +} + +SYSCALL_DEFINE5(execveat, + int, fd, const char __user *, filename, + const char __user *const __user *, argv, + const char __user *const __user *, envp, + int, flags) +{ + int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0; + + return do_execveat(fd, + getname_flags(filename, lookup_flags, NULL), + argv, envp, flags); +} + +#ifdef CONFIG_COMPAT +COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename, + const compat_uptr_t __user *, argv, + const compat_uptr_t __user *, envp) +{ + return compat_do_execve(getname(filename), argv, envp); +} + +COMPAT_SYSCALL_DEFINE5(execveat, int, fd, + const char __user *, filename, + const compat_uptr_t __user *, argv, + const compat_uptr_t __user *, envp, + int, flags) +{ + int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0; + + return compat_do_execveat(fd, + getname_flags(filename, lookup_flags, NULL), + argv, envp, flags); +} +#endif |