diff options
Diffstat (limited to 'fs/exec.c')
| -rw-r--r-- | fs/exec.c | 2183 |
1 files changed, 2183 insertions, 0 deletions
diff --git a/fs/exec.c b/fs/exec.c new file mode 100644 index 0000000000..2f2b0acec4 --- /dev/null +++ b/fs/exec.c @@ -0,0 +1,2183 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * 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/kernel_read_file.h> +#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/sched/mm.h> +#include <linux/sched/coredump.h> +#include <linux/sched/signal.h> +#include <linux/sched/numa_balancing.h> +#include <linux/sched/task.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/kmod.h> +#include <linux/fsnotify.h> +#include <linux/fs_struct.h> +#include <linux/oom.h> +#include <linux/compat.h> +#include <linux/vmalloc.h> +#include <linux/io_uring.h> +#include <linux/syscall_user_dispatch.h> +#include <linux/coredump.h> +#include <linux/time_namespace.h> +#include <linux/user_events.h> + +#include <linux/uaccess.h> +#include <asm/mmu_context.h> +#include <asm/tlb.h> + +#include <trace/events/task.h> +#include "internal.h" + +#include <trace/events/sched.h> + +static int bprm_creds_from_file(struct linux_binprm *bprm); + +int suid_dumpable = 0; + +static LIST_HEAD(formats); +static DEFINE_RWLOCK(binfmt_lock); + +void __register_binfmt(struct linux_binfmt * fmt, int insert) +{ + 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); +} + +bool path_noexec(const struct path *path) +{ + return (path->mnt->mnt_flags & MNT_NOEXEC) || + (path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC); +} + +#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 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, + .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; + + /* + * may_open() has already checked for this, so it should be + * impossible to trip now. But we need to be extra cautious + * and check again at the very end too. + */ + error = -EACCES; + if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode) || + path_noexec(&file->f_path))) + goto exit; + + 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; + struct vm_area_struct *vma = bprm->vma; + struct mm_struct *mm = bprm->mm; + int ret; + + /* + * Avoid relying on expanding the stack down in GUP (which + * does not work for STACK_GROWSUP anyway), and just do it + * by hand ahead of time. + */ + if (write && pos < vma->vm_start) { + mmap_write_lock(mm); + ret = expand_downwards(vma, pos); + if (unlikely(ret < 0)) { + mmap_write_unlock(mm); + return NULL; + } + mmap_write_downgrade(mm); + } else + mmap_read_lock(mm); + + /* + * We are doing an exec(). 'current' is the process + * doing the exec and 'mm' is the new process's mm. + */ + ret = get_user_pages_remote(mm, pos, 1, + write ? FOLL_WRITE : 0, + &page, NULL); + mmap_read_unlock(mm); + if (ret <= 0) + return NULL; + + if (write) + acct_arg_size(bprm, vma_pages(vma)); + + return page; +} + +static void put_arg_page(struct page *page) +{ + put_page(page); +} + +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 = vm_area_alloc(mm); + if (!vma) + return -ENOMEM; + vma_set_anonymous(vma); + + if (mmap_write_lock_killable(mm)) { + err = -EINTR; + goto err_free; + } + + /* + * 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; + vm_flags_init(vma, VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP); + vma->vm_page_prot = vm_get_page_prot(vma->vm_flags); + + err = insert_vm_struct(mm, vma); + if (err) + goto err; + + mm->stack_vm = mm->total_vm = 1; + mmap_write_unlock(mm); + bprm->p = vma->vm_end - sizeof(void *); + return 0; +err: + mmap_write_unlock(mm); +err_free: + bprm->vma = NULL; + vm_area_free(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; + + /* Save current stack limit for all calculations made during exec. */ + task_lock(current->group_leader); + bprm->rlim_stack = current->signal->rlim[RLIMIT_STACK]; + task_unlock(current->group_leader); + + 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; +} + +static int count_strings_kernel(const char *const *argv) +{ + int i; + + if (!argv) + return 0; + + for (i = 0; argv[i]; ++i) { + if (i >= MAX_ARG_STRINGS) + return -E2BIG; + if (fatal_signal_pending(current)) + return -ERESTARTNOHAND; + cond_resched(); + } + return i; +} + +static int bprm_stack_limits(struct linux_binprm *bprm) +{ + unsigned long limit, ptr_size; + + /* + * Limit to 1/4 of the max stack size or 3/4 of _STK_LIM + * (whichever is smaller) 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. + */ + limit = _STK_LIM / 4 * 3; + limit = min(limit, bprm->rlim_stack.rlim_cur / 4); + /* + * We've historically supported up to 32 pages (ARG_MAX) + * of argument strings even with small stacks + */ + limit = max_t(unsigned long, limit, ARG_MAX); + /* + * We must account for the size of all the argv and envp pointers to + * the argv and envp strings, since they will also take up space in + * the stack. They aren't stored until much later when we can't + * signal to the parent that the child has run out of stack space. + * Instead, calculate it here so it's possible to fail gracefully. + * + * In the case of argc = 0, make sure there is space for adding a + * empty string (which will bump argc to 1), to ensure confused + * userspace programs don't start processing from argv[1], thinking + * argc can never be 0, to keep them from walking envp by accident. + * See do_execveat_common(). + */ + ptr_size = (max(bprm->argc, 1) + bprm->envc) * sizeof(void *); + if (limit <= ptr_size) + return -E2BIG; + limit -= ptr_size; + + bprm->argmin = bprm->p - limit; + return 0; +} + +/* + * '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 backwards. */ + pos = bprm->p; + str += len; + bprm->p -= len; +#ifdef CONFIG_MMU + if (bprm->p < bprm->argmin) + goto out; +#endif + + 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_dcache_page(kmapped_page); + kunmap_local(kaddr); + put_arg_page(kmapped_page); + } + kmapped_page = page; + kaddr = kmap_local_page(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_dcache_page(kmapped_page); + kunmap_local(kaddr); + put_arg_page(kmapped_page); + } + return ret; +} + +/* + * Copy and argument/environment string from the kernel to the processes stack. + */ +int copy_string_kernel(const char *arg, struct linux_binprm *bprm) +{ + int len = strnlen(arg, MAX_ARG_STRLEN) + 1 /* terminating NUL */; + unsigned long pos = bprm->p; + + if (len == 0) + return -EFAULT; + if (!valid_arg_len(bprm, len)) + return -E2BIG; + + /* We're going to work our way backwards. */ + arg += len; + bprm->p -= len; + if (IS_ENABLED(CONFIG_MMU) && bprm->p < bprm->argmin) + return -E2BIG; + + while (len > 0) { + unsigned int bytes_to_copy = min_t(unsigned int, len, + min_not_zero(offset_in_page(pos), PAGE_SIZE)); + struct page *page; + + pos -= bytes_to_copy; + arg -= bytes_to_copy; + len -= bytes_to_copy; + + page = get_arg_page(bprm, pos, 1); + if (!page) + return -E2BIG; + flush_arg_page(bprm, pos & PAGE_MASK, page); + memcpy_to_page(page, offset_in_page(pos), arg, bytes_to_copy); + put_arg_page(page); + } + + return 0; +} +EXPORT_SYMBOL(copy_string_kernel); + +static int copy_strings_kernel(int argc, const char *const *argv, + struct linux_binprm *bprm) +{ + while (argc-- > 0) { + int ret = copy_string_kernel(argv[argc], bprm); + if (ret < 0) + return ret; + if (fatal_signal_pending(current)) + return -ERESTARTNOHAND; + cond_resched(); + } + return 0; +} + +#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; + VMA_ITERATOR(vmi, mm, new_start); + struct vm_area_struct *next; + 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 != vma_next(&vmi)) + return -EFAULT; + + vma_iter_prev_range(&vmi); + /* + * cover the whole range: [new_start, old_end) + */ + if (vma_expand(&vmi, 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); + next = vma_next(&vmi); + 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, + next ? 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, + next ? next->vm_start : USER_PGTABLES_CEILING); + } + tlb_finish_mmu(&tlb); + + vma_prev(&vmi); + /* Shrink the vma to just the new range */ + return vma_shrink(&vmi, vma, new_start, new_end, vma->vm_pgoff); +} + +/* + * 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; + struct mmu_gather tlb; + struct vma_iterator vmi; + +#ifdef CONFIG_STACK_GROWSUP + /* Limit stack size */ + stack_base = bprm->rlim_stack.rlim_max; + + stack_base = calc_max_stack_size(stack_base); + + /* 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; + + if (mmap_write_lock_killable(mm)) + return -EINTR; + + 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; + + vma_iter_init(&vmi, mm, vma->vm_start); + + tlb_gather_mmu(&tlb, mm); + ret = mprotect_fixup(&vmi, &tlb, vma, &prev, vma->vm_start, vma->vm_end, + vm_flags); + tlb_finish_mmu(&tlb); + + if (ret) + goto out_unlock; + BUG_ON(prev != vma); + + if (unlikely(vm_flags & VM_EXEC)) { + pr_warn_once("process '%pD4' started with executable stack\n", + bprm->file); + } + + /* 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 */ + vm_flags_clear(vma, 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 = bprm->rlim_stack.rlim_cur & PAGE_MASK; + + stack_expand = min(rlim_stack, stack_size + stack_expand); + +#ifdef CONFIG_STACK_GROWSUP + stack_base = vma->vm_start + stack_expand; +#else + stack_base = vma->vm_end - stack_expand; +#endif + current->mm->start_stack = bprm->p; + ret = expand_stack_locked(vma, stack_base); + if (ret) + ret = -EFAULT; + +out_unlock: + mmap_write_unlock(mm); + return ret; +} +EXPORT_SYMBOL(setup_arg_pages); + +#else + +/* + * Transfer the program arguments and environment from the holding pages + * onto the stack. The provided stack pointer is adjusted accordingly. + */ +int transfer_args_to_stack(struct linux_binprm *bprm, + unsigned long *sp_location) +{ + unsigned long index, stop, sp; + int ret = 0; + + stop = bprm->p >> PAGE_SHIFT; + sp = *sp_location; + + for (index = MAX_ARG_PAGES - 1; index >= stop; index--) { + unsigned int offset = index == stop ? bprm->p & ~PAGE_MASK : 0; + char *src = kmap_local_page(bprm->page[index]) + offset; + sp -= PAGE_SIZE - offset; + if (copy_to_user((void *) sp, src, PAGE_SIZE - offset) != 0) + ret = -EFAULT; + kunmap_local(src); + if (ret) + goto out; + } + + *sp_location = sp; + +out: + return ret; +} +EXPORT_SYMBOL(transfer_args_to_stack); + +#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, + .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; + + /* + * may_open() has already checked for this, so it should be + * impossible to trip now. But we need to be extra cautious + * and check again at the very end too. + */ + err = -EACCES; + if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode) || + path_noexec(&file->f_path))) + goto exit; + + err = deny_write_access(file); + if (err) + goto exit; + +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); + +#if defined(CONFIG_BINFMT_FLAT) || defined(CONFIG_BINFMT_ELF_FDPIC) +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_user_range(addr, addr + len); + return res; +} +EXPORT_SYMBOL(read_code); +#endif + +/* + * Maps the mm_struct mm into the current task struct. + * On success, this function returns with exec_update_lock + * held for writing. + */ +static int exec_mmap(struct mm_struct *mm) +{ + struct task_struct *tsk; + struct mm_struct *old_mm, *active_mm; + int ret; + + /* Notify parent that we're no longer interested in the old VM */ + tsk = current; + old_mm = current->mm; + exec_mm_release(tsk, old_mm); + if (old_mm) + sync_mm_rss(old_mm); + + ret = down_write_killable(&tsk->signal->exec_update_lock); + if (ret) + return ret; + + if (old_mm) { + /* + * If there is a pending fatal signal perhaps a signal + * whose default action is to create a coredump get + * out and die instead of going through with the exec. + */ + ret = mmap_read_lock_killable(old_mm); + if (ret) { + up_write(&tsk->signal->exec_update_lock); + return ret; + } + } + + task_lock(tsk); + membarrier_exec_mmap(mm); + + local_irq_disable(); + active_mm = tsk->active_mm; + tsk->active_mm = mm; + tsk->mm = mm; + mm_init_cid(mm); + /* + * This prevents preemption while active_mm is being loaded and + * it and mm are being updated, which could cause problems for + * lazy tlb mm refcounting when these are updated by context + * switches. Not all architectures can handle irqs off over + * activate_mm yet. + */ + if (!IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM)) + local_irq_enable(); + activate_mm(active_mm, mm); + if (IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM)) + local_irq_enable(); + lru_gen_add_mm(mm); + task_unlock(tsk); + lru_gen_use_mm(mm); + if (old_mm) { + mmap_read_unlock(old_mm); + 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_lazy_tlb(active_mm); + return 0; +} + +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 ((sig->flags & SIGNAL_GROUP_EXIT) || sig->group_exec_task) { + /* + * Another group action in progress, just + * return so that the signal is processed. + */ + spin_unlock_irq(lock); + return -EAGAIN; + } + + sig->group_exec_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 (__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 (;;) { + cgroup_threadgroup_change_begin(tsk); + write_lock_irq(&tasklist_lock); + /* + * Do this under tasklist_lock to ensure that + * exit_notify() can't miss ->group_exec_task + */ + sig->notify_count = -1; + if (likely(leader->exit_state)) + break; + __set_current_state(TASK_KILLABLE); + write_unlock_irq(&tasklist_lock); + cgroup_threadgroup_change_end(tsk); + schedule(); + if (__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->start_boottime = leader->start_boottime; + + BUG_ON(!same_thread_group(leader, 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. + */ + exchange_tids(tsk, leader); + transfer_pid(leader, tsk, PIDTYPE_TGID); + 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 won't block again waiting for this thread. + */ + if (unlikely(leader->ptrace)) + __wake_up_parent(leader, leader->parent); + write_unlock_irq(&tasklist_lock); + cgroup_threadgroup_change_end(tsk); + + release_task(leader); + } + + sig->group_exec_task = NULL; + sig->notify_count = 0; + +no_thread_group: + /* we have changed execution domain */ + tsk->exit_signal = SIGCHLD; + + BUG_ON(!thread_group_leader(tsk)); + return 0; + +killed: + /* protects against exit_notify() and __exit_signal() */ + read_lock(&tasklist_lock); + sig->group_exec_task = NULL; + sig->notify_count = 0; + read_unlock(&tasklist_lock); + return -EAGAIN; +} + + +/* + * 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 unshare_sighand(struct task_struct *me) +{ + struct sighand_struct *oldsighand = me->sighand; + + if (refcount_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; + + refcount_set(&newsighand->count, 1); + + write_lock_irq(&tasklist_lock); + spin_lock(&oldsighand->siglock); + memcpy(newsighand->action, oldsighand->action, + sizeof(newsighand->action)); + rcu_assign_pointer(me->sighand, newsighand); + spin_unlock(&oldsighand->siglock); + write_unlock_irq(&tasklist_lock); + + __cleanup_sighand(oldsighand); + } + return 0; +} + +char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk) +{ + task_lock(tsk); + /* Always NUL terminated and zero-padded */ + strscpy_pad(buf, tsk->comm, buf_size); + 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); + strscpy_pad(tsk->comm, buf, sizeof(tsk->comm)); + task_unlock(tsk); + perf_event_comm(tsk, exec); +} + +/* + * Calling this is the point of no return. None of the failures will be + * seen by userspace since either the process is already taking a fatal + * signal (via de_thread() or coredump), or will have SEGV raised + * (after exec_mmap()) by search_binary_handler (see below). + */ +int begin_new_exec(struct linux_binprm * bprm) +{ + struct task_struct *me = current; + int retval; + + /* Once we are committed compute the creds */ + retval = bprm_creds_from_file(bprm); + if (retval) + return retval; + + /* + * Ensure all future errors are fatal. + */ + bprm->point_of_no_return = true; + + /* + * Make this the only thread in the thread group. + */ + retval = de_thread(me); + if (retval) + goto out; + + /* + * Cancel any io_uring activity across execve + */ + io_uring_task_cancel(); + + /* Ensure the files table is not shared. */ + retval = unshare_files(); + if (retval) + goto out; + + /* + * Must be called _before_ exec_mmap() as bprm->mm is + * not visible until then. Doing it here also ensures + * we don't race against replace_mm_exe_file(). + */ + retval = set_mm_exe_file(bprm->mm, bprm->file); + if (retval) + goto out; + + /* If the binary is not readable then enforce mm->dumpable=0 */ + would_dump(bprm, bprm->file); + if (bprm->have_execfd) + would_dump(bprm, bprm->executable); + + /* + * Release all of the old mmap stuff + */ + acct_arg_size(bprm, 0); + retval = exec_mmap(bprm->mm); + if (retval) + goto out; + + bprm->mm = NULL; + + retval = exec_task_namespaces(); + if (retval) + goto out_unlock; + +#ifdef CONFIG_POSIX_TIMERS + spin_lock_irq(&me->sighand->siglock); + posix_cpu_timers_exit(me); + spin_unlock_irq(&me->sighand->siglock); + exit_itimers(me); + flush_itimer_signals(); +#endif + + /* + * Make the signal table private. + */ + retval = unshare_sighand(me); + if (retval) + goto out_unlock; + + me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | + PF_NOFREEZE | PF_NO_SETAFFINITY); + flush_thread(); + me->personality &= ~bprm->per_clear; + + clear_syscall_work_syscall_user_dispatch(me); + + /* + * We have to apply CLOEXEC before we change whether the process is + * dumpable (in setup_new_exec) to avoid a race with a process in userspace + * trying to access the should-be-closed file descriptors of a process + * undergoing exec(2). + */ + do_close_on_exec(me->files); + + if (bprm->secureexec) { + /* Make sure parent cannot signal privileged process. */ + me->pdeath_signal = 0; + + /* + * For secureexec, reset the stack limit to sane default to + * avoid bad behavior from the prior rlimits. This has to + * happen before arch_pick_mmap_layout(), which examines + * RLIMIT_STACK, but after the point of no return to avoid + * needing to clean up the change on failure. + */ + if (bprm->rlim_stack.rlim_cur > _STK_LIM) + bprm->rlim_stack.rlim_cur = _STK_LIM; + } + + me->sas_ss_sp = me->sas_ss_size = 0; + + /* + * Figure out dumpability. Note that this checking only of current + * is wrong, but userspace depends on it. This should be testing + * bprm->secureexec instead. + */ + if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP || + !(uid_eq(current_euid(), current_uid()) && + gid_eq(current_egid(), current_gid()))) + set_dumpable(current->mm, suid_dumpable); + else + set_dumpable(current->mm, SUID_DUMP_USER); + + perf_event_exec(); + __set_task_comm(me, kbasename(bprm->filename), true); + + /* An exec changes our domain. We are no longer part of the thread + group */ + WRITE_ONCE(me->self_exec_id, me->self_exec_id + 1); + flush_signal_handlers(me, 0); + + retval = set_cred_ucounts(bprm->cred); + if (retval < 0) + goto out_unlock; + + /* + * install the new credentials for this executable + */ + 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(me->mm) != SUID_DUMP_USER) + perf_event_exit_task(me); + /* + * 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); + + /* Pass the opened binary to the interpreter. */ + if (bprm->have_execfd) { + retval = get_unused_fd_flags(0); + if (retval < 0) + goto out_unlock; + fd_install(retval, bprm->executable); + bprm->executable = NULL; + bprm->execfd = retval; + } + return 0; + +out_unlock: + up_write(&me->signal->exec_update_lock); + if (!bprm->cred) + mutex_unlock(&me->signal->cred_guard_mutex); + +out: + return retval; +} +EXPORT_SYMBOL(begin_new_exec); + +void would_dump(struct linux_binprm *bprm, struct file *file) +{ + struct inode *inode = file_inode(file); + struct mnt_idmap *idmap = file_mnt_idmap(file); + if (inode_permission(idmap, inode, MAY_READ) < 0) { + struct user_namespace *old, *user_ns; + bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP; + + /* Ensure mm->user_ns contains the executable */ + user_ns = old = bprm->mm->user_ns; + while ((user_ns != &init_user_ns) && + !privileged_wrt_inode_uidgid(user_ns, idmap, inode)) + user_ns = user_ns->parent; + + if (old != user_ns) { + bprm->mm->user_ns = get_user_ns(user_ns); + put_user_ns(old); + } + } +} +EXPORT_SYMBOL(would_dump); + +void setup_new_exec(struct linux_binprm * bprm) +{ + /* Setup things that can depend upon the personality */ + struct task_struct *me = current; + + arch_pick_mmap_layout(me->mm, &bprm->rlim_stack); + + arch_setup_new_exec(); + + /* 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 + */ + me->mm->task_size = TASK_SIZE; + up_write(&me->signal->exec_update_lock); + mutex_unlock(&me->signal->cred_guard_mutex); +} +EXPORT_SYMBOL(setup_new_exec); + +/* Runs immediately before start_thread() takes over. */ +void finalize_exec(struct linux_binprm *bprm) +{ + /* Store any stack rlimit changes before starting thread. */ + task_lock(current->group_leader); + current->signal->rlim[RLIMIT_STACK] = bprm->rlim_stack; + task_unlock(current->group_leader); +} +EXPORT_SYMBOL(finalize_exec); + +/* + * Prepare credentials and lock ->cred_guard_mutex. + * setup_new_exec() commits the new creds and drops the lock. + * Or, if exec fails before, free_bprm() should release ->cred + * and unlock. + */ +static 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) +{ + if (bprm->mm) { + acct_arg_size(bprm, 0); + mmput(bprm->mm); + } + 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 (bprm->executable) + fput(bprm->executable); + /* If a binfmt changed the interp, free it. */ + if (bprm->interp != bprm->filename) + kfree(bprm->interp); + kfree(bprm->fdpath); + kfree(bprm); +} + +static struct linux_binprm *alloc_bprm(int fd, struct filename *filename) +{ + struct linux_binprm *bprm = kzalloc(sizeof(*bprm), GFP_KERNEL); + int retval = -ENOMEM; + if (!bprm) + goto out; + + if (fd == AT_FDCWD || filename->name[0] == '/') { + bprm->filename = filename->name; + } else { + if (filename->name[0] == '\0') + bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d", fd); + else + bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d/%s", + fd, filename->name); + if (!bprm->fdpath) + goto out_free; + + bprm->filename = bprm->fdpath; + } + bprm->interp = bprm->filename; + + retval = bprm_mm_init(bprm); + if (retval) + goto out_free; + return bprm; + +out_free: + free_bprm(bprm); +out: + return ERR_PTR(retval); +} + +int bprm_change_interp(const 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); + +/* + * 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) + 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; + + /* + * If another task is sharing our fs, we cannot safely + * suid exec because the differently privileged task + * will be able to manipulate the current directory, etc. + * It would be nice to force an unshare instead... + */ + 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 file *file) +{ + /* Handle suid and sgid on files */ + struct mnt_idmap *idmap; + struct inode *inode = file_inode(file); + unsigned int mode; + vfsuid_t vfsuid; + vfsgid_t vfsgid; + + if (!mnt_may_suid(file->f_path.mnt)) + return; + + if (task_no_new_privs(current)) + return; + + mode = READ_ONCE(inode->i_mode); + if (!(mode & (S_ISUID|S_ISGID))) + return; + + idmap = file_mnt_idmap(file); + + /* Be careful if suid/sgid is set */ + inode_lock(inode); + + /* reload atomically mode/uid/gid now that lock held */ + mode = inode->i_mode; + vfsuid = i_uid_into_vfsuid(idmap, inode); + vfsgid = i_gid_into_vfsgid(idmap, inode); + inode_unlock(inode); + + /* We ignore suid/sgid if there are no mappings for them in the ns */ + if (!vfsuid_has_mapping(bprm->cred->user_ns, vfsuid) || + !vfsgid_has_mapping(bprm->cred->user_ns, vfsgid)) + return; + + if (mode & S_ISUID) { + bprm->per_clear |= PER_CLEAR_ON_SETID; + bprm->cred->euid = vfsuid_into_kuid(vfsuid); + } + + if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { + bprm->per_clear |= PER_CLEAR_ON_SETID; + bprm->cred->egid = vfsgid_into_kgid(vfsgid); + } +} + +/* + * Compute brpm->cred based upon the final binary. + */ +static int bprm_creds_from_file(struct linux_binprm *bprm) +{ + /* Compute creds based on which file? */ + struct file *file = bprm->execfd_creds ? bprm->executable : bprm->file; + + bprm_fill_uid(bprm, file); + return security_bprm_creds_from_file(bprm, file); +} + +/* + * Fill the binprm structure from the inode. + * Read the first BINPRM_BUF_SIZE bytes + * + * This may be called multiple times for binary chains (scripts for example). + */ +static int prepare_binprm(struct linux_binprm *bprm) +{ + loff_t pos = 0; + + memset(bprm->buf, 0, BINPRM_BUF_SIZE); + return kernel_read(bprm->file, bprm->buf, BINPRM_BUF_SIZE, &pos); +} + +/* + * 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_local_page(page); + + for (; offset < PAGE_SIZE && kaddr[offset]; + offset++, bprm->p++) + ; + + kunmap_local(kaddr); + put_arg_page(page); + } 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 + */ +static int search_binary_handler(struct linux_binprm *bprm) +{ + bool need_retry = IS_ENABLED(CONFIG_MODULES); + struct linux_binfmt *fmt; + int retval; + + retval = prepare_binprm(bprm); + if (retval < 0) + return retval; + + 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); + + retval = fmt->load_binary(bprm); + + read_lock(&binfmt_lock); + put_binfmt(fmt); + if (bprm->point_of_no_return || (retval != -ENOEXEC)) { + 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; +} + +/* binfmt handlers will call back into begin_new_exec() on success. */ +static int exec_binprm(struct linux_binprm *bprm) +{ + pid_t old_pid, old_vpid; + int ret, depth; + + /* 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(); + + /* This allows 4 levels of binfmt rewrites before failing hard. */ + for (depth = 0;; depth++) { + struct file *exec; + if (depth > 5) + return -ELOOP; + + ret = search_binary_handler(bprm); + if (ret < 0) + return ret; + if (!bprm->interpreter) + break; + + exec = bprm->file; + bprm->file = bprm->interpreter; + bprm->interpreter = NULL; + + allow_write_access(exec); + if (unlikely(bprm->have_execfd)) { + if (bprm->executable) { + fput(exec); + return -ENOEXEC; + } + bprm->executable = exec; + } else + fput(exec); + } + + audit_bprm(bprm); + trace_sched_process_exec(current, old_pid, bprm); + ptrace_event(PTRACE_EVENT_EXEC, old_vpid); + proc_exec_connector(current); + return 0; +} + +/* + * sys_execve() executes a new program. + */ +static int bprm_execve(struct linux_binprm *bprm, + int fd, struct filename *filename, int flags) +{ + struct file *file; + int retval; + + retval = prepare_bprm_creds(bprm); + if (retval) + return retval; + + /* + * Check for unsafe execution states before exec_binprm(), which + * will call back into begin_new_exec(), into bprm_creds_from_file(), + * where setuid-ness is evaluated. + */ + check_unsafe_exec(bprm); + current->in_execve = 1; + sched_mm_cid_before_execve(current); + + file = do_open_execat(fd, filename, flags); + retval = PTR_ERR(file); + if (IS_ERR(file)) + goto out_unmark; + + sched_exec(); + + bprm->file = file; + /* + * Record that a name derived from an O_CLOEXEC fd will be + * inaccessible after exec. This allows the code in exec to + * choose to fail when the executable is not mmaped into the + * interpreter and an open file descriptor is not passed to + * the interpreter. This makes for a better user experience + * than having the interpreter start and then immediately fail + * when it finds the executable is inaccessible. + */ + if (bprm->fdpath && get_close_on_exec(fd)) + bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE; + + /* Set the unchanging part of bprm->cred */ + retval = security_bprm_creds_for_exec(bprm); + if (retval) + goto out; + + retval = exec_binprm(bprm); + if (retval < 0) + goto out; + + sched_mm_cid_after_execve(current); + /* execve succeeded */ + current->fs->in_exec = 0; + current->in_execve = 0; + rseq_execve(current); + user_events_execve(current); + acct_update_integrals(current); + task_numa_free(current, false); + return retval; + +out: + /* + * If past the point of no return ensure the code never + * returns to the userspace process. Use an existing fatal + * signal if present otherwise terminate the process with + * SIGSEGV. + */ + if (bprm->point_of_no_return && !fatal_signal_pending(current)) + force_fatal_sig(SIGSEGV); + +out_unmark: + sched_mm_cid_after_execve(current); + current->fs->in_exec = 0; + current->in_execve = 0; + + return retval; +} + +static int do_execveat_common(int fd, struct filename *filename, + struct user_arg_ptr argv, + struct user_arg_ptr envp, + int flags) +{ + struct linux_binprm *bprm; + 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) && + is_rlimit_overlimit(current_ucounts(), UCOUNT_RLIMIT_NPROC, 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; + + bprm = alloc_bprm(fd, filename); + if (IS_ERR(bprm)) { + retval = PTR_ERR(bprm); + goto out_ret; + } + + retval = count(argv, MAX_ARG_STRINGS); + if (retval == 0) + pr_warn_once("process '%s' launched '%s' with NULL argv: empty string added\n", + current->comm, bprm->filename); + if (retval < 0) + goto out_free; + bprm->argc = retval; + + retval = count(envp, MAX_ARG_STRINGS); + if (retval < 0) + goto out_free; + bprm->envc = retval; + + retval = bprm_stack_limits(bprm); + if (retval < 0) + goto out_free; + + retval = copy_string_kernel(bprm->filename, bprm); + if (retval < 0) + goto out_free; + bprm->exec = bprm->p; + + retval = copy_strings(bprm->envc, envp, bprm); + if (retval < 0) + goto out_free; + + retval = copy_strings(bprm->argc, argv, bprm); + if (retval < 0) + goto out_free; + + /* + * When argv is empty, add an empty string ("") as argv[0] to + * ensure confused userspace programs that start processing + * from argv[1] won't end up walking envp. See also + * bprm_stack_limits(). + */ + if (bprm->argc == 0) { + retval = copy_string_kernel("", bprm); + if (retval < 0) + goto out_free; + bprm->argc = 1; + } + + retval = bprm_execve(bprm, fd, filename, flags); +out_free: + free_bprm(bprm); + +out_ret: + putname(filename); + return retval; +} + +int kernel_execve(const char *kernel_filename, + const char *const *argv, const char *const *envp) +{ + struct filename *filename; + struct linux_binprm *bprm; + int fd = AT_FDCWD; + int retval; + + /* It is non-sense for kernel threads to call execve */ + if (WARN_ON_ONCE(current->flags & PF_KTHREAD)) + return -EINVAL; + + filename = getname_kernel(kernel_filename); + if (IS_ERR(filename)) + return PTR_ERR(filename); + + bprm = alloc_bprm(fd, filename); + if (IS_ERR(bprm)) { + retval = PTR_ERR(bprm); + goto out_ret; + } + + retval = count_strings_kernel(argv); + if (WARN_ON_ONCE(retval == 0)) + retval = -EINVAL; + if (retval < 0) + goto out_free; + bprm->argc = retval; + + retval = count_strings_kernel(envp); + if (retval < 0) + goto out_free; + bprm->envc = retval; + + retval = bprm_stack_limits(bprm); + if (retval < 0) + goto out_free; + + retval = copy_string_kernel(bprm->filename, bprm); + if (retval < 0) + goto out_free; + bprm->exec = bprm->p; + + retval = copy_strings_kernel(bprm->envc, envp, bprm); + if (retval < 0) + goto out_free; + + retval = copy_strings_kernel(bprm->argc, argv, bprm); + if (retval < 0) + goto out_free; + + retval = bprm_execve(bprm, fd, filename, 0); +out_free: + free_bprm(bprm); +out_ret: + putname(filename); + return retval; +} + +static 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); +} + +static 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) +{ + if (WARN_ON((unsigned)value > SUID_DUMP_ROOT)) + return; + + set_mask_bits(&mm->flags, MMF_DUMPABLE_MASK, value); +} + +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) +{ + return do_execveat(fd, + getname_uflags(filename, flags), + 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) +{ + return compat_do_execveat(fd, + getname_uflags(filename, flags), + argv, envp, flags); +} +#endif + +#ifdef CONFIG_SYSCTL + +static int proc_dointvec_minmax_coredump(struct ctl_table *table, int write, + void *buffer, size_t *lenp, loff_t *ppos) +{ + int error = proc_dointvec_minmax(table, write, buffer, lenp, ppos); + + if (!error) + validate_coredump_safety(); + return error; +} + +static struct ctl_table fs_exec_sysctls[] = { + { + .procname = "suid_dumpable", + .data = &suid_dumpable, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec_minmax_coredump, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_TWO, + }, + { } +}; + +static int __init init_fs_exec_sysctls(void) +{ + register_sysctl_init("fs", fs_exec_sysctls); + return 0; +} + +fs_initcall(init_fs_exec_sysctls); +#endif /* CONFIG_SYSCTL */ |