1/*
   2 *  linux/fs/exec.c
   3 *
   4 *  Copyright (C) 1991, 1992  Linus Torvalds
   5 */
   6
   7/*
   8 * #!-checking implemented by tytso.
   9 */
  10/*
  11 * Demand-loading implemented 01.12.91 - no need to read anything but
  12 * the header into memory. The inode of the executable is put into
  13 * "current->executable", and page faults do the actual loading. Clean.
  14 *
  15 * Once more I can proudly say that linux stood up to being changed: it
  16 * was less than 2 hours work to get demand-loading completely implemented.
  17 *
  18 * Demand loading changed July 1993 by Eric Youngdale.   Use mmap instead,
  19 * current->executable is only used by the procfs.  This allows a dispatch
  20 * table to check for several different types  of binary formats.  We keep
  21 * trying until we recognize the file or we run out of supported binary
  22 * formats. 
  23 */
  24
  25#include <linux/slab.h>
  26#include <linux/file.h>
  27#include <linux/fdtable.h>
  28#include <linux/mm.h>
  29#include <linux/vmacache.h>
  30#include <linux/stat.h>
  31#include <linux/fcntl.h>
  32#include <linux/swap.h>
  33#include <linux/string.h>
  34#include <linux/init.h>
  35#include <linux/pagemap.h>
  36#include <linux/perf_event.h>
  37#include <linux/highmem.h>
  38#include <linux/spinlock.h>
  39#include <linux/key.h>
  40#include <linux/personality.h>
  41#include <linux/binfmts.h>
  42#include <linux/utsname.h>
  43#include <linux/pid_namespace.h>
  44#include <linux/module.h>
  45#include <linux/namei.h>
  46#include <linux/mount.h>
  47#include <linux/security.h>
  48#include <linux/syscalls.h>
  49#include <linux/tsacct_kern.h>
  50#include <linux/cn_proc.h>
  51#include <linux/audit.h>
  52#include <linux/tracehook.h>
  53#include <linux/kmod.h>
  54#include <linux/fsnotify.h>
  55#include <linux/fs_struct.h>
  56#include <linux/pipe_fs_i.h>
  57#include <linux/oom.h>
  58#include <linux/compat.h>
  59#include <linux/vmalloc.h>
  60
  61#include <asm/uaccess.h>
  62#include <asm/mmu_context.h>
  63#include <asm/tlb.h>
  64
  65#include <trace/events/task.h>
  66#include "internal.h"
  67
  68#include <trace/events/sched.h>
  69
  70int suid_dumpable = 0;
  71
  72static LIST_HEAD(formats);
  73static DEFINE_RWLOCK(binfmt_lock);
  74
  75void __register_binfmt(struct linux_binfmt * fmt, int insert)
  76{
  77	BUG_ON(!fmt);
  78	if (WARN_ON(!fmt->load_binary))
  79		return;
  80	write_lock(&binfmt_lock);
  81	insert ? list_add(&fmt->lh, &formats) :
  82		 list_add_tail(&fmt->lh, &formats);
  83	write_unlock(&binfmt_lock);
  84}
  85
  86EXPORT_SYMBOL(__register_binfmt);
  87
  88void unregister_binfmt(struct linux_binfmt * fmt)
  89{
  90	write_lock(&binfmt_lock);
  91	list_del(&fmt->lh);
  92	write_unlock(&binfmt_lock);
  93}
  94
  95EXPORT_SYMBOL(unregister_binfmt);
  96
  97static inline void put_binfmt(struct linux_binfmt * fmt)
  98{
  99	module_put(fmt->module);
 100}
 101
 102bool path_noexec(const struct path *path)
 103{
 104	return (path->mnt->mnt_flags & MNT_NOEXEC) ||
 105	       (path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC);
 106}
 107
 108#ifdef CONFIG_USELIB
 109/*
 110 * Note that a shared library must be both readable and executable due to
 111 * security reasons.
 112 *
 113 * Also note that we take the address to load from from the file itself.
 114 */
 115SYSCALL_DEFINE1(uselib, const char __user *, library)
 116{
 117	struct linux_binfmt *fmt;
 118	struct file *file;
 119	struct filename *tmp = getname(library);
 120	int error = PTR_ERR(tmp);
 121	static const struct open_flags uselib_flags = {
 122		.open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
 123		.acc_mode = MAY_READ | MAY_EXEC,
 124		.intent = LOOKUP_OPEN,
 125		.lookup_flags = LOOKUP_FOLLOW,
 126	};
 127
 128	if (IS_ERR(tmp))
 129		goto out;
 130
 131	file = do_filp_open(AT_FDCWD, tmp, &uselib_flags);
 132	putname(tmp);
 133	error = PTR_ERR(file);
 134	if (IS_ERR(file))
 135		goto out;
 136
 137	error = -EINVAL;
 138	if (!S_ISREG(file_inode(file)->i_mode))
 139		goto exit;
 140
 141	error = -EACCES;
 142	if (path_noexec(&file->f_path))
 143		goto exit;
 144
 145	fsnotify_open(file);
 146
 147	error = -ENOEXEC;
 148
 149	read_lock(&binfmt_lock);
 150	list_for_each_entry(fmt, &formats, lh) {
 151		if (!fmt->load_shlib)
 152			continue;
 153		if (!try_module_get(fmt->module))
 154			continue;
 155		read_unlock(&binfmt_lock);
 156		error = fmt->load_shlib(file);
 157		read_lock(&binfmt_lock);
 158		put_binfmt(fmt);
 159		if (error != -ENOEXEC)
 160			break;
 161	}
 162	read_unlock(&binfmt_lock);
 163exit:
 164	fput(file);
 165out:
 166  	return error;
 167}
 168#endif /* #ifdef CONFIG_USELIB */
 169
 170#ifdef CONFIG_MMU
 171/*
 172 * The nascent bprm->mm is not visible until exec_mmap() but it can
 173 * use a lot of memory, account these pages in current->mm temporary
 174 * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we
 175 * change the counter back via acct_arg_size(0).
 176 */
 177static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 178{
 179	struct mm_struct *mm = current->mm;
 180	long diff = (long)(pages - bprm->vma_pages);
 181
 182	if (!mm || !diff)
 183		return;
 184
 185	bprm->vma_pages = pages;
 186	add_mm_counter(mm, MM_ANONPAGES, diff);
 187}
 188
 189static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 190		int write)
 191{
 192	struct page *page;
 193	int ret;
 194
 195#ifdef CONFIG_STACK_GROWSUP
 196	if (write) {
 197		ret = expand_downwards(bprm->vma, pos);
 198		if (ret < 0)
 199			return NULL;
 200	}
 201#endif
 202	/*
 203	 * We are doing an exec().  'current' is the process
 204	 * doing the exec and bprm->mm is the new process's mm.
 205	 */
 206	ret = get_user_pages_remote(current, bprm->mm, pos, 1, write,
 207			1, &page, NULL);
 208	if (ret <= 0)
 209		return NULL;
 210
 211	if (write) {
 212		unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
 213		struct rlimit *rlim;
 214
 215		acct_arg_size(bprm, size / PAGE_SIZE);
 216
 217		/*
 218		 * We've historically supported up to 32 pages (ARG_MAX)
 219		 * of argument strings even with small stacks
 220		 */
 221		if (size <= ARG_MAX)
 222			return page;
 223
 224		/*
 225		 * Limit to 1/4-th the stack size for the argv+env strings.
 226		 * This ensures that:
 227		 *  - the remaining binfmt code will not run out of stack space,
 228		 *  - the program will have a reasonable amount of stack left
 229		 *    to work from.
 230		 */
 231		rlim = current->signal->rlim;
 232		if (size > ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur) / 4) {
 233			put_page(page);
 234			return NULL;
 235		}
 236	}
 237
 238	return page;
 239}
 240
 241static void put_arg_page(struct page *page)
 242{
 243	put_page(page);
 244}
 245
 246static void free_arg_page(struct linux_binprm *bprm, int i)
 247{
 248}
 249
 250static void free_arg_pages(struct linux_binprm *bprm)
 251{
 252}
 253
 254static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 255		struct page *page)
 256{
 257	flush_cache_page(bprm->vma, pos, page_to_pfn(page));
 258}
 259
 260static int __bprm_mm_init(struct linux_binprm *bprm)
 261{
 262	int err;
 263	struct vm_area_struct *vma = NULL;
 264	struct mm_struct *mm = bprm->mm;
 265
 266	bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
 267	if (!vma)
 268		return -ENOMEM;
 269
 270	down_write(&mm->mmap_sem);
 271	vma->vm_mm = mm;
 272
 273	/*
 274	 * Place the stack at the largest stack address the architecture
 275	 * supports. Later, we'll move this to an appropriate place. We don't
 276	 * use STACK_TOP because that can depend on attributes which aren't
 277	 * configured yet.
 278	 */
 279	BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
 280	vma->vm_end = STACK_TOP_MAX;
 281	vma->vm_start = vma->vm_end - PAGE_SIZE;
 282	vma->vm_flags = VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP;
 283	vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
 284	INIT_LIST_HEAD(&vma->anon_vma_chain);
 285
 286	err = insert_vm_struct(mm, vma);
 287	if (err)
 288		goto err;
 289
 290	mm->stack_vm = mm->total_vm = 1;
 291	arch_bprm_mm_init(mm, vma);
 292	up_write(&mm->mmap_sem);
 293	bprm->p = vma->vm_end - sizeof(void *);
 294	return 0;
 295err:
 296	up_write(&mm->mmap_sem);
 297	bprm->vma = NULL;
 298	kmem_cache_free(vm_area_cachep, vma);
 299	return err;
 300}
 301
 302static bool valid_arg_len(struct linux_binprm *bprm, long len)
 303{
 304	return len <= MAX_ARG_STRLEN;
 305}
 306
 307#else
 308
 309static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 310{
 311}
 312
 313static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 314		int write)
 315{
 316	struct page *page;
 317
 318	page = bprm->page[pos / PAGE_SIZE];
 319	if (!page && write) {
 320		page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
 321		if (!page)
 322			return NULL;
 323		bprm->page[pos / PAGE_SIZE] = page;
 324	}
 325
 326	return page;
 327}
 328
 329static void put_arg_page(struct page *page)
 330{
 331}
 332
 333static void free_arg_page(struct linux_binprm *bprm, int i)
 334{
 335	if (bprm->page[i]) {
 336		__free_page(bprm->page[i]);
 337		bprm->page[i] = NULL;
 338	}
 339}
 340
 341static void free_arg_pages(struct linux_binprm *bprm)
 342{
 343	int i;
 344
 345	for (i = 0; i < MAX_ARG_PAGES; i++)
 346		free_arg_page(bprm, i);
 347}
 348
 349static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 350		struct page *page)
 351{
 352}
 353
 354static int __bprm_mm_init(struct linux_binprm *bprm)
 355{
 356	bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
 357	return 0;
 358}
 359
 360static bool valid_arg_len(struct linux_binprm *bprm, long len)
 361{
 362	return len <= bprm->p;
 363}
 364
 365#endif /* CONFIG_MMU */
 366
 367/*
 368 * Create a new mm_struct and populate it with a temporary stack
 369 * vm_area_struct.  We don't have enough context at this point to set the stack
 370 * flags, permissions, and offset, so we use temporary values.  We'll update
 371 * them later in setup_arg_pages().
 372 */
 373static int bprm_mm_init(struct linux_binprm *bprm)
 374{
 375	int err;
 376	struct mm_struct *mm = NULL;
 377
 378	bprm->mm = mm = mm_alloc();
 379	err = -ENOMEM;
 380	if (!mm)
 381		goto err;
 382
 
 
 
 
 383	err = __bprm_mm_init(bprm);
 384	if (err)
 385		goto err;
 386
 387	return 0;
 388
 389err:
 390	if (mm) {
 391		bprm->mm = NULL;
 392		mmdrop(mm);
 393	}
 394
 395	return err;
 396}
 397
 398struct user_arg_ptr {
 399#ifdef CONFIG_COMPAT
 400	bool is_compat;
 401#endif
 402	union {
 403		const char __user *const __user *native;
 404#ifdef CONFIG_COMPAT
 405		const compat_uptr_t __user *compat;
 406#endif
 407	} ptr;
 408};
 409
 410static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
 411{
 412	const char __user *native;
 413
 414#ifdef CONFIG_COMPAT
 415	if (unlikely(argv.is_compat)) {
 416		compat_uptr_t compat;
 417
 418		if (get_user(compat, argv.ptr.compat + nr))
 419			return ERR_PTR(-EFAULT);
 420
 421		return compat_ptr(compat);
 422	}
 423#endif
 424
 425	if (get_user(native, argv.ptr.native + nr))
 426		return ERR_PTR(-EFAULT);
 427
 428	return native;
 429}
 430
 431/*
 432 * count() counts the number of strings in array ARGV.
 433 */
 434static int count(struct user_arg_ptr argv, int max)
 435{
 436	int i = 0;
 437
 438	if (argv.ptr.native != NULL) {
 439		for (;;) {
 440			const char __user *p = get_user_arg_ptr(argv, i);
 441
 442			if (!p)
 443				break;
 444
 445			if (IS_ERR(p))
 446				return -EFAULT;
 447
 448			if (i >= max)
 449				return -E2BIG;
 450			++i;
 451
 452			if (fatal_signal_pending(current))
 453				return -ERESTARTNOHAND;
 454			cond_resched();
 455		}
 456	}
 457	return i;
 458}
 459
 460/*
 461 * 'copy_strings()' copies argument/environment strings from the old
 462 * processes's memory to the new process's stack.  The call to get_user_pages()
 463 * ensures the destination page is created and not swapped out.
 464 */
 465static int copy_strings(int argc, struct user_arg_ptr argv,
 466			struct linux_binprm *bprm)
 467{
 468	struct page *kmapped_page = NULL;
 469	char *kaddr = NULL;
 470	unsigned long kpos = 0;
 471	int ret;
 472
 473	while (argc-- > 0) {
 474		const char __user *str;
 475		int len;
 476		unsigned long pos;
 477
 478		ret = -EFAULT;
 479		str = get_user_arg_ptr(argv, argc);
 480		if (IS_ERR(str))
 481			goto out;
 482
 483		len = strnlen_user(str, MAX_ARG_STRLEN);
 484		if (!len)
 485			goto out;
 486
 487		ret = -E2BIG;
 488		if (!valid_arg_len(bprm, len))
 489			goto out;
 490
 491		/* We're going to work our way backwords. */
 492		pos = bprm->p;
 493		str += len;
 494		bprm->p -= len;
 495
 496		while (len > 0) {
 497			int offset, bytes_to_copy;
 498
 499			if (fatal_signal_pending(current)) {
 500				ret = -ERESTARTNOHAND;
 501				goto out;
 502			}
 503			cond_resched();
 504
 505			offset = pos % PAGE_SIZE;
 506			if (offset == 0)
 507				offset = PAGE_SIZE;
 508
 509			bytes_to_copy = offset;
 510			if (bytes_to_copy > len)
 511				bytes_to_copy = len;
 512
 513			offset -= bytes_to_copy;
 514			pos -= bytes_to_copy;
 515			str -= bytes_to_copy;
 516			len -= bytes_to_copy;
 517
 518			if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
 519				struct page *page;
 520
 521				page = get_arg_page(bprm, pos, 1);
 522				if (!page) {
 523					ret = -E2BIG;
 524					goto out;
 525				}
 526
 527				if (kmapped_page) {
 528					flush_kernel_dcache_page(kmapped_page);
 529					kunmap(kmapped_page);
 530					put_arg_page(kmapped_page);
 531				}
 532				kmapped_page = page;
 533				kaddr = kmap(kmapped_page);
 534				kpos = pos & PAGE_MASK;
 535				flush_arg_page(bprm, kpos, kmapped_page);
 536			}
 537			if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
 538				ret = -EFAULT;
 539				goto out;
 540			}
 541		}
 542	}
 543	ret = 0;
 544out:
 545	if (kmapped_page) {
 546		flush_kernel_dcache_page(kmapped_page);
 547		kunmap(kmapped_page);
 548		put_arg_page(kmapped_page);
 549	}
 550	return ret;
 551}
 552
 553/*
 554 * Like copy_strings, but get argv and its values from kernel memory.
 555 */
 556int copy_strings_kernel(int argc, const char *const *__argv,
 557			struct linux_binprm *bprm)
 558{
 559	int r;
 560	mm_segment_t oldfs = get_fs();
 561	struct user_arg_ptr argv = {
 562		.ptr.native = (const char __user *const  __user *)__argv,
 563	};
 564
 565	set_fs(KERNEL_DS);
 566	r = copy_strings(argc, argv, bprm);
 567	set_fs(oldfs);
 568
 569	return r;
 570}
 571EXPORT_SYMBOL(copy_strings_kernel);
 572
 573#ifdef CONFIG_MMU
 574
 575/*
 576 * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
 577 * the binfmt code determines where the new stack should reside, we shift it to
 578 * its final location.  The process proceeds as follows:
 579 *
 580 * 1) Use shift to calculate the new vma endpoints.
 581 * 2) Extend vma to cover both the old and new ranges.  This ensures the
 582 *    arguments passed to subsequent functions are consistent.
 583 * 3) Move vma's page tables to the new range.
 584 * 4) Free up any cleared pgd range.
 585 * 5) Shrink the vma to cover only the new range.
 586 */
 587static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
 588{
 589	struct mm_struct *mm = vma->vm_mm;
 590	unsigned long old_start = vma->vm_start;
 591	unsigned long old_end = vma->vm_end;
 592	unsigned long length = old_end - old_start;
 593	unsigned long new_start = old_start - shift;
 594	unsigned long new_end = old_end - shift;
 595	struct mmu_gather tlb;
 596
 597	BUG_ON(new_start > new_end);
 598
 599	/*
 600	 * ensure there are no vmas between where we want to go
 601	 * and where we are
 602	 */
 603	if (vma != find_vma(mm, new_start))
 604		return -EFAULT;
 605
 606	/*
 607	 * cover the whole range: [new_start, old_end)
 608	 */
 609	if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL))
 610		return -ENOMEM;
 611
 612	/*
 613	 * move the page tables downwards, on failure we rely on
 614	 * process cleanup to remove whatever mess we made.
 615	 */
 616	if (length != move_page_tables(vma, old_start,
 617				       vma, new_start, length, false))
 618		return -ENOMEM;
 619
 620	lru_add_drain();
 621	tlb_gather_mmu(&tlb, mm, old_start, old_end);
 622	if (new_end > old_start) {
 623		/*
 624		 * when the old and new regions overlap clear from new_end.
 625		 */
 626		free_pgd_range(&tlb, new_end, old_end, new_end,
 627			vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
 628	} else {
 629		/*
 630		 * otherwise, clean from old_start; this is done to not touch
 631		 * the address space in [new_end, old_start) some architectures
 632		 * have constraints on va-space that make this illegal (IA64) -
 633		 * for the others its just a little faster.
 634		 */
 635		free_pgd_range(&tlb, old_start, old_end, new_end,
 636			vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
 637	}
 638	tlb_finish_mmu(&tlb, old_start, old_end);
 639
 640	/*
 641	 * Shrink the vma to just the new range.  Always succeeds.
 642	 */
 643	vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
 644
 645	return 0;
 646}
 647
 648/*
 649 * Finalizes the stack vm_area_struct. The flags and permissions are updated,
 650 * the stack is optionally relocated, and some extra space is added.
 651 */
 652int setup_arg_pages(struct linux_binprm *bprm,
 653		    unsigned long stack_top,
 654		    int executable_stack)
 655{
 656	unsigned long ret;
 657	unsigned long stack_shift;
 658	struct mm_struct *mm = current->mm;
 659	struct vm_area_struct *vma = bprm->vma;
 660	struct vm_area_struct *prev = NULL;
 661	unsigned long vm_flags;
 662	unsigned long stack_base;
 663	unsigned long stack_size;
 664	unsigned long stack_expand;
 665	unsigned long rlim_stack;
 666
 667#ifdef CONFIG_STACK_GROWSUP
 668	/* Limit stack size */
 669	stack_base = rlimit_max(RLIMIT_STACK);
 670	if (stack_base > STACK_SIZE_MAX)
 671		stack_base = STACK_SIZE_MAX;
 672
 673	/* Add space for stack randomization. */
 674	stack_base += (STACK_RND_MASK << PAGE_SHIFT);
 675
 676	/* Make sure we didn't let the argument array grow too large. */
 677	if (vma->vm_end - vma->vm_start > stack_base)
 678		return -ENOMEM;
 679
 680	stack_base = PAGE_ALIGN(stack_top - stack_base);
 681
 682	stack_shift = vma->vm_start - stack_base;
 683	mm->arg_start = bprm->p - stack_shift;
 684	bprm->p = vma->vm_end - stack_shift;
 685#else
 686	stack_top = arch_align_stack(stack_top);
 687	stack_top = PAGE_ALIGN(stack_top);
 688
 689	if (unlikely(stack_top < mmap_min_addr) ||
 690	    unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
 691		return -ENOMEM;
 692
 693	stack_shift = vma->vm_end - stack_top;
 694
 695	bprm->p -= stack_shift;
 696	mm->arg_start = bprm->p;
 697#endif
 698
 699	if (bprm->loader)
 700		bprm->loader -= stack_shift;
 701	bprm->exec -= stack_shift;
 702
 703	down_write(&mm->mmap_sem);
 704	vm_flags = VM_STACK_FLAGS;
 705
 706	/*
 707	 * Adjust stack execute permissions; explicitly enable for
 708	 * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
 709	 * (arch default) otherwise.
 710	 */
 711	if (unlikely(executable_stack == EXSTACK_ENABLE_X))
 712		vm_flags |= VM_EXEC;
 713	else if (executable_stack == EXSTACK_DISABLE_X)
 714		vm_flags &= ~VM_EXEC;
 715	vm_flags |= mm->def_flags;
 716	vm_flags |= VM_STACK_INCOMPLETE_SETUP;
 717
 718	ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
 719			vm_flags);
 720	if (ret)
 721		goto out_unlock;
 722	BUG_ON(prev != vma);
 723
 724	/* Move stack pages down in memory. */
 725	if (stack_shift) {
 726		ret = shift_arg_pages(vma, stack_shift);
 727		if (ret)
 728			goto out_unlock;
 729	}
 730
 731	/* mprotect_fixup is overkill to remove the temporary stack flags */
 732	vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP;
 733
 734	stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
 735	stack_size = vma->vm_end - vma->vm_start;
 736	/*
 737	 * Align this down to a page boundary as expand_stack
 738	 * will align it up.
 739	 */
 740	rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK;
 741#ifdef CONFIG_STACK_GROWSUP
 742	if (stack_size + stack_expand > rlim_stack)
 743		stack_base = vma->vm_start + rlim_stack;
 744	else
 745		stack_base = vma->vm_end + stack_expand;
 746#else
 747	if (stack_size + stack_expand > rlim_stack)
 748		stack_base = vma->vm_end - rlim_stack;
 749	else
 750		stack_base = vma->vm_start - stack_expand;
 751#endif
 752	current->mm->start_stack = bprm->p;
 753	ret = expand_stack(vma, stack_base);
 754	if (ret)
 755		ret = -EFAULT;
 756
 757out_unlock:
 758	up_write(&mm->mmap_sem);
 759	return ret;
 760}
 761EXPORT_SYMBOL(setup_arg_pages);
 762
 763#endif /* CONFIG_MMU */
 764
 765static struct file *do_open_execat(int fd, struct filename *name, int flags)
 766{
 767	struct file *file;
 768	int err;
 769	struct open_flags open_exec_flags = {
 770		.open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
 771		.acc_mode = MAY_EXEC,
 772		.intent = LOOKUP_OPEN,
 773		.lookup_flags = LOOKUP_FOLLOW,
 774	};
 775
 776	if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
 777		return ERR_PTR(-EINVAL);
 778	if (flags & AT_SYMLINK_NOFOLLOW)
 779		open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW;
 780	if (flags & AT_EMPTY_PATH)
 781		open_exec_flags.lookup_flags |= LOOKUP_EMPTY;
 782
 783	file = do_filp_open(fd, name, &open_exec_flags);
 784	if (IS_ERR(file))
 785		goto out;
 786
 787	err = -EACCES;
 788	if (!S_ISREG(file_inode(file)->i_mode))
 789		goto exit;
 790
 791	if (path_noexec(&file->f_path))
 792		goto exit;
 793
 
 
 794	err = deny_write_access(file);
 795	if (err)
 796		goto exit;
 797
 798	if (name->name[0] != '\0')
 799		fsnotify_open(file);
 800
 801out:
 802	return file;
 803
 804exit:
 805	fput(file);
 806	return ERR_PTR(err);
 807}
 808
 809struct file *open_exec(const char *name)
 810{
 811	struct filename *filename = getname_kernel(name);
 812	struct file *f = ERR_CAST(filename);
 813
 814	if (!IS_ERR(filename)) {
 815		f = do_open_execat(AT_FDCWD, filename, 0);
 816		putname(filename);
 817	}
 818	return f;
 819}
 820EXPORT_SYMBOL(open_exec);
 821
 822int kernel_read(struct file *file, loff_t offset,
 823		char *addr, unsigned long count)
 824{
 825	mm_segment_t old_fs;
 826	loff_t pos = offset;
 827	int result;
 828
 829	old_fs = get_fs();
 830	set_fs(get_ds());
 831	/* The cast to a user pointer is valid due to the set_fs() */
 832	result = vfs_read(file, (void __user *)addr, count, &pos);
 833	set_fs(old_fs);
 834	return result;
 835}
 836
 837EXPORT_SYMBOL(kernel_read);
 838
 839int kernel_read_file(struct file *file, void **buf, loff_t *size,
 840		     loff_t max_size, enum kernel_read_file_id id)
 841{
 842	loff_t i_size, pos;
 843	ssize_t bytes = 0;
 844	int ret;
 845
 846	if (!S_ISREG(file_inode(file)->i_mode) || max_size < 0)
 847		return -EINVAL;
 848
 849	ret = security_kernel_read_file(file, id);
 850	if (ret)
 851		return ret;
 852
 853	i_size = i_size_read(file_inode(file));
 854	if (max_size > 0 && i_size > max_size)
 855		return -EFBIG;
 856	if (i_size <= 0)
 857		return -EINVAL;
 858
 859	*buf = vmalloc(i_size);
 860	if (!*buf)
 861		return -ENOMEM;
 862
 863	pos = 0;
 864	while (pos < i_size) {
 865		bytes = kernel_read(file, pos, (char *)(*buf) + pos,
 866				    i_size - pos);
 867		if (bytes < 0) {
 868			ret = bytes;
 869			goto out;
 870		}
 871
 872		if (bytes == 0)
 873			break;
 874		pos += bytes;
 875	}
 876
 877	if (pos != i_size) {
 878		ret = -EIO;
 879		goto out;
 880	}
 881
 882	ret = security_kernel_post_read_file(file, *buf, i_size, id);
 883	if (!ret)
 884		*size = pos;
 885
 886out:
 887	if (ret < 0) {
 888		vfree(*buf);
 889		*buf = NULL;
 890	}
 891	return ret;
 892}
 893EXPORT_SYMBOL_GPL(kernel_read_file);
 894
 895int kernel_read_file_from_path(char *path, void **buf, loff_t *size,
 896			       loff_t max_size, enum kernel_read_file_id id)
 897{
 898	struct file *file;
 899	int ret;
 900
 901	if (!path || !*path)
 902		return -EINVAL;
 903
 904	file = filp_open(path, O_RDONLY, 0);
 905	if (IS_ERR(file))
 906		return PTR_ERR(file);
 907
 908	ret = kernel_read_file(file, buf, size, max_size, id);
 909	fput(file);
 910	return ret;
 911}
 912EXPORT_SYMBOL_GPL(kernel_read_file_from_path);
 913
 914int kernel_read_file_from_fd(int fd, void **buf, loff_t *size, loff_t max_size,
 915			     enum kernel_read_file_id id)
 916{
 917	struct fd f = fdget(fd);
 918	int ret = -EBADF;
 919
 920	if (!f.file)
 921		goto out;
 922
 923	ret = kernel_read_file(f.file, buf, size, max_size, id);
 924out:
 925	fdput(f);
 926	return ret;
 927}
 928EXPORT_SYMBOL_GPL(kernel_read_file_from_fd);
 929
 930ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
 931{
 932	ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
 933	if (res > 0)
 934		flush_icache_range(addr, addr + len);
 935	return res;
 936}
 937EXPORT_SYMBOL(read_code);
 938
 939static int exec_mmap(struct mm_struct *mm)
 940{
 941	struct task_struct *tsk;
 942	struct mm_struct *old_mm, *active_mm;
 943
 944	/* Notify parent that we're no longer interested in the old VM */
 945	tsk = current;
 946	old_mm = current->mm;
 947	mm_release(tsk, old_mm);
 948
 949	if (old_mm) {
 950		sync_mm_rss(old_mm);
 951		/*
 952		 * Make sure that if there is a core dump in progress
 953		 * for the old mm, we get out and die instead of going
 954		 * through with the exec.  We must hold mmap_sem around
 955		 * checking core_state and changing tsk->mm.
 956		 */
 957		down_read(&old_mm->mmap_sem);
 958		if (unlikely(old_mm->core_state)) {
 959			up_read(&old_mm->mmap_sem);
 960			return -EINTR;
 961		}
 962	}
 963	task_lock(tsk);
 964	active_mm = tsk->active_mm;
 965	tsk->mm = mm;
 966	tsk->active_mm = mm;
 967	activate_mm(active_mm, mm);
 968	tsk->mm->vmacache_seqnum = 0;
 969	vmacache_flush(tsk);
 970	task_unlock(tsk);
 971	if (old_mm) {
 972		up_read(&old_mm->mmap_sem);
 973		BUG_ON(active_mm != old_mm);
 974		setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm);
 975		mm_update_next_owner(old_mm);
 976		mmput(old_mm);
 977		return 0;
 978	}
 979	mmdrop(active_mm);
 980	return 0;
 981}
 982
 983/*
 984 * This function makes sure the current process has its own signal table,
 985 * so that flush_signal_handlers can later reset the handlers without
 986 * disturbing other processes.  (Other processes might share the signal
 987 * table via the CLONE_SIGHAND option to clone().)
 988 */
 989static int de_thread(struct task_struct *tsk)
 990{
 991	struct signal_struct *sig = tsk->signal;
 992	struct sighand_struct *oldsighand = tsk->sighand;
 993	spinlock_t *lock = &oldsighand->siglock;
 994
 995	if (thread_group_empty(tsk))
 996		goto no_thread_group;
 997
 998	/*
 999	 * Kill all other threads in the thread group.
1000	 */
1001	spin_lock_irq(lock);
1002	if (signal_group_exit(sig)) {
1003		/*
1004		 * Another group action in progress, just
1005		 * return so that the signal is processed.
1006		 */
1007		spin_unlock_irq(lock);
1008		return -EAGAIN;
1009	}
1010
1011	sig->group_exit_task = tsk;
1012	sig->notify_count = zap_other_threads(tsk);
1013	if (!thread_group_leader(tsk))
1014		sig->notify_count--;
1015
1016	while (sig->notify_count) {
1017		__set_current_state(TASK_KILLABLE);
1018		spin_unlock_irq(lock);
1019		schedule();
1020		if (unlikely(__fatal_signal_pending(tsk)))
1021			goto killed;
1022		spin_lock_irq(lock);
1023	}
1024	spin_unlock_irq(lock);
1025
1026	/*
1027	 * At this point all other threads have exited, all we have to
1028	 * do is to wait for the thread group leader to become inactive,
1029	 * and to assume its PID:
1030	 */
1031	if (!thread_group_leader(tsk)) {
1032		struct task_struct *leader = tsk->group_leader;
1033
 
1034		for (;;) {
1035			threadgroup_change_begin(tsk);
1036			write_lock_irq(&tasklist_lock);
1037			/*
1038			 * Do this under tasklist_lock to ensure that
1039			 * exit_notify() can't miss ->group_exit_task
1040			 */
1041			sig->notify_count = -1;
1042			if (likely(leader->exit_state))
1043				break;
1044			__set_current_state(TASK_KILLABLE);
1045			write_unlock_irq(&tasklist_lock);
1046			threadgroup_change_end(tsk);
1047			schedule();
1048			if (unlikely(__fatal_signal_pending(tsk)))
1049				goto killed;
1050		}
1051
1052		/*
1053		 * The only record we have of the real-time age of a
1054		 * process, regardless of execs it's done, is start_time.
1055		 * All the past CPU time is accumulated in signal_struct
1056		 * from sister threads now dead.  But in this non-leader
1057		 * exec, nothing survives from the original leader thread,
1058		 * whose birth marks the true age of this process now.
1059		 * When we take on its identity by switching to its PID, we
1060		 * also take its birthdate (always earlier than our own).
1061		 */
1062		tsk->start_time = leader->start_time;
1063		tsk->real_start_time = leader->real_start_time;
1064
1065		BUG_ON(!same_thread_group(leader, tsk));
1066		BUG_ON(has_group_leader_pid(tsk));
1067		/*
1068		 * An exec() starts a new thread group with the
1069		 * TGID of the previous thread group. Rehash the
1070		 * two threads with a switched PID, and release
1071		 * the former thread group leader:
1072		 */
1073
1074		/* Become a process group leader with the old leader's pid.
1075		 * The old leader becomes a thread of the this thread group.
1076		 * Note: The old leader also uses this pid until release_task
1077		 *       is called.  Odd but simple and correct.
1078		 */
1079		tsk->pid = leader->pid;
1080		change_pid(tsk, PIDTYPE_PID, task_pid(leader));
1081		transfer_pid(leader, tsk, PIDTYPE_PGID);
1082		transfer_pid(leader, tsk, PIDTYPE_SID);
1083
1084		list_replace_rcu(&leader->tasks, &tsk->tasks);
1085		list_replace_init(&leader->sibling, &tsk->sibling);
1086
1087		tsk->group_leader = tsk;
1088		leader->group_leader = tsk;
1089
1090		tsk->exit_signal = SIGCHLD;
1091		leader->exit_signal = -1;
1092
1093		BUG_ON(leader->exit_state != EXIT_ZOMBIE);
1094		leader->exit_state = EXIT_DEAD;
1095
1096		/*
1097		 * We are going to release_task()->ptrace_unlink() silently,
1098		 * the tracer can sleep in do_wait(). EXIT_DEAD guarantees
1099		 * the tracer wont't block again waiting for this thread.
1100		 */
1101		if (unlikely(leader->ptrace))
1102			__wake_up_parent(leader, leader->parent);
1103		write_unlock_irq(&tasklist_lock);
1104		threadgroup_change_end(tsk);
1105
1106		release_task(leader);
1107	}
1108
1109	sig->group_exit_task = NULL;
1110	sig->notify_count = 0;
1111
1112no_thread_group:
1113	/* we have changed execution domain */
1114	tsk->exit_signal = SIGCHLD;
1115
1116	exit_itimers(sig);
1117	flush_itimer_signals();
1118
1119	if (atomic_read(&oldsighand->count) != 1) {
1120		struct sighand_struct *newsighand;
1121		/*
1122		 * This ->sighand is shared with the CLONE_SIGHAND
1123		 * but not CLONE_THREAD task, switch to the new one.
1124		 */
1125		newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1126		if (!newsighand)
1127			return -ENOMEM;
1128
1129		atomic_set(&newsighand->count, 1);
1130		memcpy(newsighand->action, oldsighand->action,
1131		       sizeof(newsighand->action));
1132
1133		write_lock_irq(&tasklist_lock);
1134		spin_lock(&oldsighand->siglock);
1135		rcu_assign_pointer(tsk->sighand, newsighand);
1136		spin_unlock(&oldsighand->siglock);
1137		write_unlock_irq(&tasklist_lock);
1138
1139		__cleanup_sighand(oldsighand);
1140	}
1141
1142	BUG_ON(!thread_group_leader(tsk));
1143	return 0;
1144
1145killed:
1146	/* protects against exit_notify() and __exit_signal() */
1147	read_lock(&tasklist_lock);
1148	sig->group_exit_task = NULL;
1149	sig->notify_count = 0;
1150	read_unlock(&tasklist_lock);
1151	return -EAGAIN;
1152}
1153
1154char *get_task_comm(char *buf, struct task_struct *tsk)
1155{
1156	/* buf must be at least sizeof(tsk->comm) in size */
1157	task_lock(tsk);
1158	strncpy(buf, tsk->comm, sizeof(tsk->comm));
1159	task_unlock(tsk);
1160	return buf;
1161}
1162EXPORT_SYMBOL_GPL(get_task_comm);
1163
1164/*
1165 * These functions flushes out all traces of the currently running executable
1166 * so that a new one can be started
1167 */
1168
1169void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
1170{
1171	task_lock(tsk);
1172	trace_task_rename(tsk, buf);
1173	strlcpy(tsk->comm, buf, sizeof(tsk->comm));
1174	task_unlock(tsk);
1175	perf_event_comm(tsk, exec);
1176}
1177
1178int flush_old_exec(struct linux_binprm * bprm)
1179{
1180	int retval;
1181
1182	/*
1183	 * Make sure we have a private signal table and that
1184	 * we are unassociated from the previous thread group.
1185	 */
1186	retval = de_thread(current);
1187	if (retval)
1188		goto out;
1189
1190	/*
1191	 * Must be called _before_ exec_mmap() as bprm->mm is
1192	 * not visibile until then. This also enables the update
1193	 * to be lockless.
1194	 */
1195	set_mm_exe_file(bprm->mm, bprm->file);
1196
1197	/*
1198	 * Release all of the old mmap stuff
1199	 */
1200	acct_arg_size(bprm, 0);
1201	retval = exec_mmap(bprm->mm);
1202	if (retval)
1203		goto out;
1204
1205	bprm->mm = NULL;		/* We're using it now */
1206
1207	set_fs(USER_DS);
1208	current->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
1209					PF_NOFREEZE | PF_NO_SETAFFINITY);
1210	flush_thread();
1211	current->personality &= ~bprm->per_clear;
1212
1213	return 0;
1214
1215out:
1216	return retval;
1217}
1218EXPORT_SYMBOL(flush_old_exec);
1219
1220void would_dump(struct linux_binprm *bprm, struct file *file)
1221{
1222	if (inode_permission(file_inode(file), MAY_READ) < 0)
1223		bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
1224}
1225EXPORT_SYMBOL(would_dump);
1226
1227void setup_new_exec(struct linux_binprm * bprm)
1228{
1229	arch_pick_mmap_layout(current->mm);
1230
1231	/* This is the point of no return */
1232	current->sas_ss_sp = current->sas_ss_size = 0;
1233
1234	if (uid_eq(current_euid(), current_uid()) && gid_eq(current_egid(), current_gid()))
1235		set_dumpable(current->mm, SUID_DUMP_USER);
1236	else
1237		set_dumpable(current->mm, suid_dumpable);
1238
1239	perf_event_exec();
1240	__set_task_comm(current, kbasename(bprm->filename), true);
1241
1242	/* Set the new mm task size. We have to do that late because it may
1243	 * depend on TIF_32BIT which is only updated in flush_thread() on
1244	 * some architectures like powerpc
1245	 */
1246	current->mm->task_size = TASK_SIZE;
1247
1248	/* install the new credentials */
1249	if (!uid_eq(bprm->cred->uid, current_euid()) ||
1250	    !gid_eq(bprm->cred->gid, current_egid())) {
1251		current->pdeath_signal = 0;
1252	} else {
1253		would_dump(bprm, bprm->file);
1254		if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)
1255			set_dumpable(current->mm, suid_dumpable);
1256	}
1257
1258	/* An exec changes our domain. We are no longer part of the thread
1259	   group */
1260	current->self_exec_id++;
1261	flush_signal_handlers(current, 0);
1262	do_close_on_exec(current->files);
1263}
1264EXPORT_SYMBOL(setup_new_exec);
1265
1266/*
1267 * Prepare credentials and lock ->cred_guard_mutex.
1268 * install_exec_creds() commits the new creds and drops the lock.
1269 * Or, if exec fails before, free_bprm() should release ->cred and
1270 * and unlock.
1271 */
1272int prepare_bprm_creds(struct linux_binprm *bprm)
1273{
1274	if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
1275		return -ERESTARTNOINTR;
1276
1277	bprm->cred = prepare_exec_creds();
1278	if (likely(bprm->cred))
1279		return 0;
1280
1281	mutex_unlock(&current->signal->cred_guard_mutex);
1282	return -ENOMEM;
1283}
1284
1285static void free_bprm(struct linux_binprm *bprm)
1286{
1287	free_arg_pages(bprm);
1288	if (bprm->cred) {
1289		mutex_unlock(&current->signal->cred_guard_mutex);
1290		abort_creds(bprm->cred);
1291	}
1292	if (bprm->file) {
1293		allow_write_access(bprm->file);
1294		fput(bprm->file);
1295	}
1296	/* If a binfmt changed the interp, free it. */
1297	if (bprm->interp != bprm->filename)
1298		kfree(bprm->interp);
1299	kfree(bprm);
1300}
1301
1302int bprm_change_interp(char *interp, struct linux_binprm *bprm)
1303{
1304	/* If a binfmt changed the interp, free it first. */
1305	if (bprm->interp != bprm->filename)
1306		kfree(bprm->interp);
1307	bprm->interp = kstrdup(interp, GFP_KERNEL);
1308	if (!bprm->interp)
1309		return -ENOMEM;
1310	return 0;
1311}
1312EXPORT_SYMBOL(bprm_change_interp);
1313
1314/*
1315 * install the new credentials for this executable
1316 */
1317void install_exec_creds(struct linux_binprm *bprm)
1318{
1319	security_bprm_committing_creds(bprm);
1320
1321	commit_creds(bprm->cred);
1322	bprm->cred = NULL;
1323
1324	/*
1325	 * Disable monitoring for regular users
1326	 * when executing setuid binaries. Must
1327	 * wait until new credentials are committed
1328	 * by commit_creds() above
1329	 */
1330	if (get_dumpable(current->mm) != SUID_DUMP_USER)
1331		perf_event_exit_task(current);
1332	/*
1333	 * cred_guard_mutex must be held at least to this point to prevent
1334	 * ptrace_attach() from altering our determination of the task's
1335	 * credentials; any time after this it may be unlocked.
1336	 */
1337	security_bprm_committed_creds(bprm);
1338	mutex_unlock(&current->signal->cred_guard_mutex);
1339}
1340EXPORT_SYMBOL(install_exec_creds);
1341
1342/*
1343 * determine how safe it is to execute the proposed program
1344 * - the caller must hold ->cred_guard_mutex to protect against
1345 *   PTRACE_ATTACH or seccomp thread-sync
1346 */
1347static void check_unsafe_exec(struct linux_binprm *bprm)
1348{
1349	struct task_struct *p = current, *t;
1350	unsigned n_fs;
1351
1352	if (p->ptrace) {
1353		if (p->ptrace & PT_PTRACE_CAP)
1354			bprm->unsafe |= LSM_UNSAFE_PTRACE_CAP;
1355		else
1356			bprm->unsafe |= LSM_UNSAFE_PTRACE;
1357	}
1358
1359	/*
1360	 * This isn't strictly necessary, but it makes it harder for LSMs to
1361	 * mess up.
1362	 */
1363	if (task_no_new_privs(current))
1364		bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;
1365
1366	t = p;
1367	n_fs = 1;
1368	spin_lock(&p->fs->lock);
1369	rcu_read_lock();
1370	while_each_thread(p, t) {
1371		if (t->fs == p->fs)
1372			n_fs++;
1373	}
1374	rcu_read_unlock();
1375
1376	if (p->fs->users > n_fs)
1377		bprm->unsafe |= LSM_UNSAFE_SHARE;
1378	else
1379		p->fs->in_exec = 1;
1380	spin_unlock(&p->fs->lock);
1381}
1382
1383static void bprm_fill_uid(struct linux_binprm *bprm)
1384{
1385	struct inode *inode;
1386	unsigned int mode;
1387	kuid_t uid;
1388	kgid_t gid;
1389
1390	/* clear any previous set[ug]id data from a previous binary */
1391	bprm->cred->euid = current_euid();
1392	bprm->cred->egid = current_egid();
1393
1394	if (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)
1395		return;
1396
1397	if (task_no_new_privs(current))
1398		return;
1399
1400	inode = file_inode(bprm->file);
1401	mode = READ_ONCE(inode->i_mode);
1402	if (!(mode & (S_ISUID|S_ISGID)))
1403		return;
1404
1405	/* Be careful if suid/sgid is set */
1406	inode_lock(inode);
1407
1408	/* reload atomically mode/uid/gid now that lock held */
1409	mode = inode->i_mode;
1410	uid = inode->i_uid;
1411	gid = inode->i_gid;
1412	inode_unlock(inode);
1413
1414	/* We ignore suid/sgid if there are no mappings for them in the ns */
1415	if (!kuid_has_mapping(bprm->cred->user_ns, uid) ||
1416		 !kgid_has_mapping(bprm->cred->user_ns, gid))
1417		return;
1418
1419	if (mode & S_ISUID) {
1420		bprm->per_clear |= PER_CLEAR_ON_SETID;
1421		bprm->cred->euid = uid;
1422	}
1423
1424	if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1425		bprm->per_clear |= PER_CLEAR_ON_SETID;
1426		bprm->cred->egid = gid;
1427	}
1428}
1429
1430/*
1431 * Fill the binprm structure from the inode.
1432 * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
1433 *
1434 * This may be called multiple times for binary chains (scripts for example).
1435 */
1436int prepare_binprm(struct linux_binprm *bprm)
1437{
 
 
1438	int retval;
1439
1440	bprm_fill_uid(bprm);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1441
1442	/* fill in binprm security blob */
1443	retval = security_bprm_set_creds(bprm);
1444	if (retval)
1445		return retval;
1446	bprm->cred_prepared = 1;
1447
1448	memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1449	return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
1450}
1451
1452EXPORT_SYMBOL(prepare_binprm);
1453
1454/*
1455 * Arguments are '\0' separated strings found at the location bprm->p
1456 * points to; chop off the first by relocating brpm->p to right after
1457 * the first '\0' encountered.
1458 */
1459int remove_arg_zero(struct linux_binprm *bprm)
1460{
1461	int ret = 0;
1462	unsigned long offset;
1463	char *kaddr;
1464	struct page *page;
1465
1466	if (!bprm->argc)
1467		return 0;
1468
1469	do {
1470		offset = bprm->p & ~PAGE_MASK;
1471		page = get_arg_page(bprm, bprm->p, 0);
1472		if (!page) {
1473			ret = -EFAULT;
1474			goto out;
1475		}
1476		kaddr = kmap_atomic(page);
1477
1478		for (; offset < PAGE_SIZE && kaddr[offset];
1479				offset++, bprm->p++)
1480			;
1481
1482		kunmap_atomic(kaddr);
1483		put_arg_page(page);
1484
1485		if (offset == PAGE_SIZE)
1486			free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1);
1487	} while (offset == PAGE_SIZE);
1488
1489	bprm->p++;
1490	bprm->argc--;
1491	ret = 0;
1492
1493out:
1494	return ret;
1495}
1496EXPORT_SYMBOL(remove_arg_zero);
1497
1498#define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1499/*
1500 * cycle the list of binary formats handler, until one recognizes the image
1501 */
1502int search_binary_handler(struct linux_binprm *bprm)
1503{
1504	bool need_retry = IS_ENABLED(CONFIG_MODULES);
1505	struct linux_binfmt *fmt;
1506	int retval;
1507
1508	/* This allows 4 levels of binfmt rewrites before failing hard. */
1509	if (bprm->recursion_depth > 5)
1510		return -ELOOP;
1511
1512	retval = security_bprm_check(bprm);
1513	if (retval)
1514		return retval;
1515
1516	retval = -ENOENT;
1517 retry:
1518	read_lock(&binfmt_lock);
1519	list_for_each_entry(fmt, &formats, lh) {
1520		if (!try_module_get(fmt->module))
1521			continue;
1522		read_unlock(&binfmt_lock);
1523		bprm->recursion_depth++;
1524		retval = fmt->load_binary(bprm);
1525		read_lock(&binfmt_lock);
1526		put_binfmt(fmt);
1527		bprm->recursion_depth--;
1528		if (retval < 0 && !bprm->mm) {
1529			/* we got to flush_old_exec() and failed after it */
1530			read_unlock(&binfmt_lock);
1531			force_sigsegv(SIGSEGV, current);
1532			return retval;
1533		}
1534		if (retval != -ENOEXEC || !bprm->file) {
1535			read_unlock(&binfmt_lock);
1536			return retval;
1537		}
 
 
1538	}
1539	read_unlock(&binfmt_lock);
1540
1541	if (need_retry) {
1542		if (printable(bprm->buf[0]) && printable(bprm->buf[1]) &&
1543		    printable(bprm->buf[2]) && printable(bprm->buf[3]))
1544			return retval;
1545		if (request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2)) < 0)
1546			return retval;
1547		need_retry = false;
1548		goto retry;
1549	}
1550
1551	return retval;
1552}
1553EXPORT_SYMBOL(search_binary_handler);
1554
1555static int exec_binprm(struct linux_binprm *bprm)
1556{
1557	pid_t old_pid, old_vpid;
1558	int ret;
1559
1560	/* Need to fetch pid before load_binary changes it */
1561	old_pid = current->pid;
1562	rcu_read_lock();
1563	old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
1564	rcu_read_unlock();
1565
1566	ret = search_binary_handler(bprm);
1567	if (ret >= 0) {
1568		audit_bprm(bprm);
1569		trace_sched_process_exec(current, old_pid, bprm);
1570		ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
1571		proc_exec_connector(current);
1572	}
1573
1574	return ret;
1575}
1576
1577/*
1578 * sys_execve() executes a new program.
1579 */
1580static int do_execveat_common(int fd, struct filename *filename,
1581			      struct user_arg_ptr argv,
1582			      struct user_arg_ptr envp,
1583			      int flags)
1584{
1585	char *pathbuf = NULL;
1586	struct linux_binprm *bprm;
1587	struct file *file;
1588	struct files_struct *displaced;
1589	int retval;
1590
1591	if (IS_ERR(filename))
1592		return PTR_ERR(filename);
1593
1594	/*
1595	 * We move the actual failure in case of RLIMIT_NPROC excess from
1596	 * set*uid() to execve() because too many poorly written programs
1597	 * don't check setuid() return code.  Here we additionally recheck
1598	 * whether NPROC limit is still exceeded.
1599	 */
1600	if ((current->flags & PF_NPROC_EXCEEDED) &&
1601	    atomic_read(&current_user()->processes) > rlimit(RLIMIT_NPROC)) {
1602		retval = -EAGAIN;
1603		goto out_ret;
1604	}
1605
1606	/* We're below the limit (still or again), so we don't want to make
1607	 * further execve() calls fail. */
1608	current->flags &= ~PF_NPROC_EXCEEDED;
1609
1610	retval = unshare_files(&displaced);
1611	if (retval)
1612		goto out_ret;
1613
1614	retval = -ENOMEM;
1615	bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1616	if (!bprm)
1617		goto out_files;
1618
1619	retval = prepare_bprm_creds(bprm);
1620	if (retval)
1621		goto out_free;
1622
1623	check_unsafe_exec(bprm);
1624	current->in_execve = 1;
1625
1626	file = do_open_execat(fd, filename, flags);
1627	retval = PTR_ERR(file);
1628	if (IS_ERR(file))
1629		goto out_unmark;
1630
1631	sched_exec();
1632
1633	bprm->file = file;
1634	if (fd == AT_FDCWD || filename->name[0] == '/') {
1635		bprm->filename = filename->name;
1636	} else {
1637		if (filename->name[0] == '\0')
1638			pathbuf = kasprintf(GFP_TEMPORARY, "/dev/fd/%d", fd);
1639		else
1640			pathbuf = kasprintf(GFP_TEMPORARY, "/dev/fd/%d/%s",
1641					    fd, filename->name);
1642		if (!pathbuf) {
1643			retval = -ENOMEM;
1644			goto out_unmark;
1645		}
1646		/*
1647		 * Record that a name derived from an O_CLOEXEC fd will be
1648		 * inaccessible after exec. Relies on having exclusive access to
1649		 * current->files (due to unshare_files above).
1650		 */
1651		if (close_on_exec(fd, rcu_dereference_raw(current->files->fdt)))
1652			bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE;
1653		bprm->filename = pathbuf;
1654	}
1655	bprm->interp = bprm->filename;
1656
1657	retval = bprm_mm_init(bprm);
1658	if (retval)
1659		goto out_unmark;
1660
1661	bprm->argc = count(argv, MAX_ARG_STRINGS);
1662	if ((retval = bprm->argc) < 0)
1663		goto out;
1664
1665	bprm->envc = count(envp, MAX_ARG_STRINGS);
1666	if ((retval = bprm->envc) < 0)
1667		goto out;
1668
1669	retval = prepare_binprm(bprm);
1670	if (retval < 0)
1671		goto out;
1672
1673	retval = copy_strings_kernel(1, &bprm->filename, bprm);
1674	if (retval < 0)
1675		goto out;
1676
1677	bprm->exec = bprm->p;
1678	retval = copy_strings(bprm->envc, envp, bprm);
1679	if (retval < 0)
1680		goto out;
1681
1682	retval = copy_strings(bprm->argc, argv, bprm);
1683	if (retval < 0)
1684		goto out;
1685
1686	retval = exec_binprm(bprm);
1687	if (retval < 0)
1688		goto out;
1689
1690	/* execve succeeded */
1691	current->fs->in_exec = 0;
1692	current->in_execve = 0;
1693	acct_update_integrals(current);
1694	task_numa_free(current);
1695	free_bprm(bprm);
1696	kfree(pathbuf);
1697	putname(filename);
1698	if (displaced)
1699		put_files_struct(displaced);
1700	return retval;
1701
1702out:
1703	if (bprm->mm) {
1704		acct_arg_size(bprm, 0);
1705		mmput(bprm->mm);
1706	}
1707
1708out_unmark:
1709	current->fs->in_exec = 0;
1710	current->in_execve = 0;
1711
1712out_free:
1713	free_bprm(bprm);
1714	kfree(pathbuf);
1715
1716out_files:
1717	if (displaced)
1718		reset_files_struct(displaced);
1719out_ret:
1720	putname(filename);
1721	return retval;
1722}
1723
1724int do_execve(struct filename *filename,
1725	const char __user *const __user *__argv,
1726	const char __user *const __user *__envp)
1727{
1728	struct user_arg_ptr argv = { .ptr.native = __argv };
1729	struct user_arg_ptr envp = { .ptr.native = __envp };
1730	return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
1731}
1732
1733int do_execveat(int fd, struct filename *filename,
1734		const char __user *const __user *__argv,
1735		const char __user *const __user *__envp,
1736		int flags)
1737{
1738	struct user_arg_ptr argv = { .ptr.native = __argv };
1739	struct user_arg_ptr envp = { .ptr.native = __envp };
1740
1741	return do_execveat_common(fd, filename, argv, envp, flags);
1742}
1743
1744#ifdef CONFIG_COMPAT
1745static int compat_do_execve(struct filename *filename,
1746	const compat_uptr_t __user *__argv,
1747	const compat_uptr_t __user *__envp)
1748{
1749	struct user_arg_ptr argv = {
1750		.is_compat = true,
1751		.ptr.compat = __argv,
1752	};
1753	struct user_arg_ptr envp = {
1754		.is_compat = true,
1755		.ptr.compat = __envp,
1756	};
1757	return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
1758}
1759
1760static int compat_do_execveat(int fd, struct filename *filename,
1761			      const compat_uptr_t __user *__argv,
1762			      const compat_uptr_t __user *__envp,
1763			      int flags)
1764{
1765	struct user_arg_ptr argv = {
1766		.is_compat = true,
1767		.ptr.compat = __argv,
1768	};
1769	struct user_arg_ptr envp = {
1770		.is_compat = true,
1771		.ptr.compat = __envp,
1772	};
1773	return do_execveat_common(fd, filename, argv, envp, flags);
1774}
1775#endif
1776
1777void set_binfmt(struct linux_binfmt *new)
1778{
1779	struct mm_struct *mm = current->mm;
1780
1781	if (mm->binfmt)
1782		module_put(mm->binfmt->module);
1783
1784	mm->binfmt = new;
1785	if (new)
1786		__module_get(new->module);
1787}
1788EXPORT_SYMBOL(set_binfmt);
1789
1790/*
1791 * set_dumpable stores three-value SUID_DUMP_* into mm->flags.
1792 */
1793void set_dumpable(struct mm_struct *mm, int value)
1794{
1795	unsigned long old, new;
1796
1797	if (WARN_ON((unsigned)value > SUID_DUMP_ROOT))
1798		return;
1799
1800	do {
1801		old = ACCESS_ONCE(mm->flags);
1802		new = (old & ~MMF_DUMPABLE_MASK) | value;
1803	} while (cmpxchg(&mm->flags, old, new) != old);
1804}
1805
1806SYSCALL_DEFINE3(execve,
1807		const char __user *, filename,
1808		const char __user *const __user *, argv,
1809		const char __user *const __user *, envp)
1810{
1811	return do_execve(getname(filename), argv, envp);
1812}
1813
1814SYSCALL_DEFINE5(execveat,
1815		int, fd, const char __user *, filename,
1816		const char __user *const __user *, argv,
1817		const char __user *const __user *, envp,
1818		int, flags)
1819{
1820	int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
1821
1822	return do_execveat(fd,
1823			   getname_flags(filename, lookup_flags, NULL),
1824			   argv, envp, flags);
1825}
1826
1827#ifdef CONFIG_COMPAT
1828COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename,
1829	const compat_uptr_t __user *, argv,
1830	const compat_uptr_t __user *, envp)
1831{
1832	return compat_do_execve(getname(filename), argv, envp);
1833}
1834
1835COMPAT_SYSCALL_DEFINE5(execveat, int, fd,
1836		       const char __user *, filename,
1837		       const compat_uptr_t __user *, argv,
1838		       const compat_uptr_t __user *, envp,
1839		       int,  flags)
1840{
1841	int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
1842
1843	return compat_do_execveat(fd,
1844				  getname_flags(filename, lookup_flags, NULL),
1845				  argv, envp, flags);
1846}
1847#endif