Merge tag 'execve-v5.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull execve updates from Kees Cook:
 "Execve and binfmt updates.

  Eric and I have stepped up to be the active maintainers of this area,
  so here's our first collection. The bulk of the work was in coredump
  handling fixes; additional details are noted below:

   - Handle unusual AT_PHDR offsets (Akira Kawata)

   - Fix initial mapping size when PT_LOADs are not ordered (Alexey
     Dobriyan)

   - Move more code under CONFIG_COREDUMP (Alexey Dobriyan)

   - Fix missing mmap_lock in file_files_note (Eric W. Biederman)

   - Remove a.out support for alpha and m68k (Eric W. Biederman)

   - Include first pages of non-exec ELF libraries in coredump (Jann
     Horn)

   - Don't write past end of notes for regset gap in coredump (Rick
     Edgecombe)

   - Comment clean-ups (Tom Rix)

   - Force single empty string when argv is empty (Kees Cook)

   - Add NULL argv selftest (Kees Cook)

   - Properly redefine PT_GNU_* in terms of PT_LOOS (Kees Cook)

   - MAINTAINERS: Update execve entry with tree (Kees Cook)

   - Introduce initial KUnit testing for binfmt_elf (Kees Cook)"

* tag 'execve-v5.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  binfmt_elf: Don't write past end of notes for regset gap
  a.out: Stop building a.out/osf1 support on alpha and m68k
  coredump: Don't compile flat_core_dump when coredumps are disabled
  coredump: Use the vma snapshot in fill_files_note
  coredump/elf: Pass coredump_params into fill_note_info
  coredump: Remove the WARN_ON in dump_vma_snapshot
  coredump: Snapshot the vmas in do_coredump
  coredump: Move definition of struct coredump_params into coredump.h
  binfmt_elf: Introduce KUnit test
  ELF: Properly redefine PT_GNU_* in terms of PT_LOOS
  MAINTAINERS: Update execve entry with more details
  exec: cleanup comments
  fs/binfmt_elf: Refactor load_elf_binary function
  fs/binfmt_elf: Fix AT_PHDR for unusual ELF files
  binfmt: move more stuff undef CONFIG_COREDUMP
  selftests/exec: Test for empty string on NULL argv
  exec: Force single empty string when argv is empty
  coredump: Also dump first pages of non-executable ELF libraries
  ELF: fix overflow in total mapping size calculation

MAINTAINERS

@@ -7234,6 +7234,9 @@ F:	net/core/of_net.c
 EXEC & BINFMT API
 R:	Eric Biederman <ebiederm@xmission.com>
 R:	Kees Cook <keescook@chromium.org>
+L:	linux-mm@kvack.org
+S:	Supported
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git for-next/execve
 F:	arch/alpha/kernel/binfmt_loader.c
 F:	arch/x86/ia32/ia32_aout.c
 F:	fs/*binfmt_*.c
@@ -7241,6 +7244,7 @@ F:	fs/exec.c
 F:	include/linux/binfmts.h
 F:	include/linux/elf.h
 F:	include/uapi/linux/binfmts.h
+F:	include/uapi/linux/elf.h
 F:	tools/testing/selftests/exec/
 N:	asm/elf.h
 N:	binfmt

arch/alpha/Kconfig

@@ -12,7 +12,6 @@ config ALPHA
 	select FORCE_PCI if !ALPHA_JENSEN
 	select PCI_DOMAINS if PCI
 	select PCI_SYSCALL if PCI
-	select HAVE_AOUT
 	select HAVE_ASM_MODVERSIONS
 	select HAVE_PCSPKR_PLATFORM
 	select HAVE_PERF_EVENTS

arch/m68k/Kconfig

@@ -17,7 +17,6 @@ config M68K
 	select GENERIC_CPU_DEVICES
 	select GENERIC_IOMAP
 	select GENERIC_IRQ_SHOW
-	select HAVE_AOUT if MMU
 	select HAVE_ASM_MODVERSIONS
 	select HAVE_DEBUG_BUGVERBOSE
 	select HAVE_EFFICIENT_UNALIGNED_ACCESS if !CPU_HAS_NO_UNALIGNED

fs/Kconfig.binfmt

@@ -28,6 +28,16 @@ config BINFMT_ELF
 	  ld.so (check the file <file:Documentation/Changes> for location and
 	  latest version).
 
+config BINFMT_ELF_KUNIT_TEST
+	bool "Build KUnit tests for ELF binary support" if !KUNIT_ALL_TESTS
+	depends on KUNIT=y && BINFMT_ELF=y
+	default KUNIT_ALL_TESTS
+	help
+	  This builds the ELF loader KUnit tests, which try to gather
+	  prior bug fixes into a regression test collection. This is really
+	  only needed for debugging. Note that with CONFIG_COMPAT=y, the
+	  compat_binfmt_elf KUnit test is also created.
+
 config COMPAT_BINFMT_ELF
 	def_bool y
 	depends on COMPAT && BINFMT_ELF

fs/binfmt_elf.c

@@ -93,7 +93,7 @@ static int elf_core_dump(struct coredump_params *cprm);
 #define ELF_CORE_EFLAGS	0
 #endif
 
-#define ELF_PAGESTART(_v) ((_v) & ~(unsigned long)(ELF_MIN_ALIGN-1))
+#define ELF_PAGESTART(_v) ((_v) & ~(int)(ELF_MIN_ALIGN-1))
 #define ELF_PAGEOFFSET(_v) ((_v) & (ELF_MIN_ALIGN-1))
 #define ELF_PAGEALIGN(_v) (((_v) + ELF_MIN_ALIGN - 1) & ~(ELF_MIN_ALIGN - 1))
 
@@ -101,8 +101,10 @@ static struct linux_binfmt elf_format = {
 	.module		= THIS_MODULE,
 	.load_binary	= load_elf_binary,
 	.load_shlib	= load_elf_library,
+#ifdef CONFIG_COREDUMP
 	.core_dump	= elf_core_dump,
 	.min_coredump	= ELF_EXEC_PAGESIZE,
+#endif
 };
 
 #define BAD_ADDR(x) (unlikely((unsigned long)(x) >= TASK_SIZE))
@@ -170,8 +172,8 @@ static int padzero(unsigned long elf_bss)
 
 static int
 create_elf_tables(struct linux_binprm *bprm, const struct elfhdr *exec,
-		unsigned long load_addr, unsigned long interp_load_addr,
-		unsigned long e_entry)
+		unsigned long interp_load_addr,
+		unsigned long e_entry, unsigned long phdr_addr)
 {
 	struct mm_struct *mm = current->mm;
 	unsigned long p = bprm->p;
@@ -257,7 +259,7 @@ create_elf_tables(struct linux_binprm *bprm, const struct elfhdr *exec,
 	NEW_AUX_ENT(AT_HWCAP, ELF_HWCAP);
 	NEW_AUX_ENT(AT_PAGESZ, ELF_EXEC_PAGESIZE);
 	NEW_AUX_ENT(AT_CLKTCK, CLOCKS_PER_SEC);
-	NEW_AUX_ENT(AT_PHDR, load_addr + exec->e_phoff);
+	NEW_AUX_ENT(AT_PHDR, phdr_addr);
 	NEW_AUX_ENT(AT_PHENT, sizeof(struct elf_phdr));
 	NEW_AUX_ENT(AT_PHNUM, exec->e_phnum);
 	NEW_AUX_ENT(AT_BASE, interp_load_addr);
@@ -399,22 +401,21 @@ static unsigned long elf_map(struct file *filep, unsigned long addr,
 	return(map_addr);
 }
 
-static unsigned long total_mapping_size(const struct elf_phdr *cmds, int nr)
+static unsigned long total_mapping_size(const struct elf_phdr *phdr, int nr)
 {
-	int i, first_idx = -1, last_idx = -1;
+	elf_addr_t min_addr = -1;
+	elf_addr_t max_addr = 0;
+	bool pt_load = false;
+	int i;
 
 	for (i = 0; i < nr; i++) {
-		if (cmds[i].p_type == PT_LOAD) {
-			last_idx = i;
-			if (first_idx == -1)
-				first_idx = i;
+		if (phdr[i].p_type == PT_LOAD) {
+			min_addr = min(min_addr, ELF_PAGESTART(phdr[i].p_vaddr));
+			max_addr = max(max_addr, phdr[i].p_vaddr + phdr[i].p_memsz);
+			pt_load = true;
 		}
 	}
-	if (first_idx == -1)
-		return 0;
-
-	return cmds[last_idx].p_vaddr + cmds[last_idx].p_memsz -
-				ELF_PAGESTART(cmds[first_idx].p_vaddr);
+	return pt_load ? (max_addr - min_addr) : 0;
 }
 
 static int elf_read(struct file *file, void *buf, size_t len, loff_t pos)
@@ -823,8 +824,8 @@ static int parse_elf_properties(struct file *f, const struct elf_phdr *phdr,
 static int load_elf_binary(struct linux_binprm *bprm)
 {
 	struct file *interpreter = NULL; /* to shut gcc up */
- 	unsigned long load_addr = 0, load_bias = 0;
-	int load_addr_set = 0;
+	unsigned long load_bias = 0, phdr_addr = 0;
+	int first_pt_load = 1;
 	unsigned long error;
 	struct elf_phdr *elf_ppnt, *elf_phdata, *interp_elf_phdata = NULL;
 	struct elf_phdr *elf_property_phdata = NULL;
@@ -1074,12 +1075,12 @@ static int load_elf_binary(struct linux_binprm *bprm)
 
 		vaddr = elf_ppnt->p_vaddr;
 		/*
-		 * The first time through the loop, load_addr_set is false:
+		 * The first time through the loop, first_pt_load is true:
 		 * layout will be calculated. Once set, use MAP_FIXED since
 		 * we know we've already safely mapped the entire region with
 		 * MAP_FIXED_NOREPLACE in the once-per-binary logic following.
 		 */
-		if (load_addr_set) {
+		if (!first_pt_load) {
 			elf_flags |= MAP_FIXED;
 		} else if (elf_ex->e_type == ET_EXEC) {
 			/*
@@ -1170,16 +1171,25 @@ static int load_elf_binary(struct linux_binprm *bprm)
 			goto out_free_dentry;
 		}
 
-		if (!load_addr_set) {
-			load_addr_set = 1;
-			load_addr = (elf_ppnt->p_vaddr - elf_ppnt->p_offset);
+		if (first_pt_load) {
+			first_pt_load = 0;
 			if (elf_ex->e_type == ET_DYN) {
 				load_bias += error -
 				             ELF_PAGESTART(load_bias + vaddr);
-				load_addr += load_bias;
 				reloc_func_desc = load_bias;
 			}
 		}
+
+		/*
+		 * Figure out which segment in the file contains the Program
+		 * Header table, and map to the associated memory address.
+		 */
+		if (elf_ppnt->p_offset <= elf_ex->e_phoff &&
+		    elf_ex->e_phoff < elf_ppnt->p_offset + elf_ppnt->p_filesz) {
+			phdr_addr = elf_ex->e_phoff - elf_ppnt->p_offset +
+				    elf_ppnt->p_vaddr;
+		}
+
 		k = elf_ppnt->p_vaddr;
 		if ((elf_ppnt->p_flags & PF_X) && k < start_code)
 			start_code = k;
@@ -1215,6 +1225,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
 	}
 
 	e_entry = elf_ex->e_entry + load_bias;
+	phdr_addr += load_bias;
 	elf_bss += load_bias;
 	elf_brk += load_bias;
 	start_code += load_bias;
@@ -1278,8 +1289,8 @@ static int load_elf_binary(struct linux_binprm *bprm)
 		goto out;
 #endif /* ARCH_HAS_SETUP_ADDITIONAL_PAGES */
 
-	retval = create_elf_tables(bprm, elf_ex,
-			  load_addr, interp_load_addr, e_entry);
+	retval = create_elf_tables(bprm, elf_ex, interp_load_addr,
+				   e_entry, phdr_addr);
 	if (retval < 0)
 		goto out;
 
@@ -1630,17 +1641,16 @@ static void fill_siginfo_note(struct memelfnote *note, user_siginfo_t *csigdata,
  *   long file_ofs
  * followed by COUNT filenames in ASCII: "FILE1" NUL "FILE2" NUL...
  */
-static int fill_files_note(struct memelfnote *note)
+static int fill_files_note(struct memelfnote *note, struct coredump_params *cprm)
 {
-	struct mm_struct *mm = current->mm;
-	struct vm_area_struct *vma;
 	unsigned count, size, names_ofs, remaining, n;
 	user_long_t *data;
 	user_long_t *start_end_ofs;
 	char *name_base, *name_curpos;
+	int i;
 
 	/* *Estimated* file count and total data size needed */
-	count = mm->map_count;
+	count = cprm->vma_count;
 	if (count > UINT_MAX / 64)
 		return -EINVAL;
 	size = count * 64;
@@ -1662,11 +1672,12 @@ static int fill_files_note(struct memelfnote *note)
 	name_base = name_curpos = ((char *)data) + names_ofs;
 	remaining = size - names_ofs;
 	count = 0;
-	for (vma = mm->mmap; vma != NULL; vma = vma->vm_next) {
+	for (i = 0; i < cprm->vma_count; i++) {
+		struct core_vma_metadata *m = &cprm->vma_meta[i];
 		struct file *file;
 		const char *filename;
 
-		file = vma->vm_file;
+		file = m->file;
 		if (!file)
 			continue;
 		filename = file_path(file, name_curpos, remaining);
@@ -1686,9 +1697,9 @@ static int fill_files_note(struct memelfnote *note)
 		memmove(name_curpos, filename, n);
 		name_curpos += n;
 
-		*start_end_ofs++ = vma->vm_start;
-		*start_end_ofs++ = vma->vm_end;
-		*start_end_ofs++ = vma->vm_pgoff;
+		*start_end_ofs++ = m->start;
+		*start_end_ofs++ = m->end;
+		*start_end_ofs++ = m->pgoff;
 		count++;
 	}
 
@@ -1699,7 +1710,7 @@ static int fill_files_note(struct memelfnote *note)
 	 * Count usually is less than mm->map_count,
 	 * we need to move filenames down.
 	 */
-	n = mm->map_count - count;
+	n = cprm->vma_count - count;
 	if (n != 0) {
 		unsigned shift_bytes = n * 3 * sizeof(data[0]);
 		memmove(name_base - shift_bytes, name_base,
@@ -1755,9 +1766,9 @@ static void do_thread_regset_writeback(struct task_struct *task,
 
 static int fill_thread_core_info(struct elf_thread_core_info *t,
 				 const struct user_regset_view *view,
-				 long signr, size_t *total)
+				 long signr, struct elf_note_info *info)
 {
-	unsigned int i;
+	unsigned int note_iter, view_iter;
 
 	/*
 	 * NT_PRSTATUS is the one special case, because the regset data
@@ -1771,17 +1782,17 @@ static int fill_thread_core_info(struct elf_thread_core_info *t,
 
 	fill_note(&t->notes[0], "CORE", NT_PRSTATUS,
 		  PRSTATUS_SIZE, &t->prstatus);
-	*total += notesize(&t->notes[0]);
+	info->size += notesize(&t->notes[0]);
 
 	do_thread_regset_writeback(t->task, &view->regsets[0]);
 
 	/*
 	 * Each other regset might generate a note too.  For each regset
-	 * that has no core_note_type or is inactive, we leave t->notes[i]
-	 * all zero and we'll know to skip writing it later.
+	 * that has no core_note_type or is inactive, skip it.
 	 */
-	for (i = 1; i < view->n; ++i) {
-		const struct user_regset *regset = &view->regsets[i];
+	note_iter = 1;
+	for (view_iter = 1; view_iter < view->n; ++view_iter) {
+		const struct user_regset *regset = &view->regsets[view_iter];
 		int note_type = regset->core_note_type;
 		bool is_fpreg = note_type == NT_PRFPREG;
 		void *data;
@@ -1797,13 +1808,17 @@ static int fill_thread_core_info(struct elf_thread_core_info *t,
 		if (ret < 0)
 			continue;
 
+		if (WARN_ON_ONCE(note_iter >= info->thread_notes))
+			break;
+
 		if (is_fpreg)
 			SET_PR_FPVALID(&t->prstatus);
 
-		fill_note(&t->notes[i], is_fpreg ? "CORE" : "LINUX",
+		fill_note(&t->notes[note_iter], is_fpreg ? "CORE" : "LINUX",
 			  note_type, ret, data);
 
-		*total += notesize(&t->notes[i]);
+		info->size += notesize(&t->notes[note_iter]);
+		note_iter++;
 	}
 
 	return 1;
@@ -1811,7 +1826,7 @@ static int fill_thread_core_info(struct elf_thread_core_info *t,
 
 static int fill_note_info(struct elfhdr *elf, int phdrs,
 			  struct elf_note_info *info,
-			  const kernel_siginfo_t *siginfo, struct pt_regs *regs)
+			  struct coredump_params *cprm)
 {
 	struct task_struct *dump_task = current;
 	const struct user_regset_view *view = task_user_regset_view(dump_task);
@@ -1883,7 +1898,7 @@ static int fill_note_info(struct elfhdr *elf, int phdrs,
 	 * Now fill in each thread's information.
 	 */
 	for (t = info->thread; t != NULL; t = t->next)
-		if (!fill_thread_core_info(t, view, siginfo->si_signo, &info->size))
+		if (!fill_thread_core_info(t, view, cprm->siginfo->si_signo, info))
 			return 0;
 
 	/*
@@ -1892,13 +1907,13 @@ static int fill_note_info(struct elfhdr *elf, int phdrs,
 	fill_psinfo(psinfo, dump_task->group_leader, dump_task->mm);
 	info->size += notesize(&info->psinfo);
 
-	fill_siginfo_note(&info->signote, &info->csigdata, siginfo);
+	fill_siginfo_note(&info->signote, &info->csigdata, cprm->siginfo);
 	info->size += notesize(&info->signote);
 
 	fill_auxv_note(&info->auxv, current->mm);
 	info->size += notesize(&info->auxv);
 
-	if (fill_files_note(&info->files) == 0)
+	if (fill_files_note(&info->files, cprm) == 0)
 		info->size += notesize(&info->files);
 
 	return 1;
@@ -2040,7 +2055,7 @@ static int elf_note_info_init(struct elf_note_info *info)
 
 static int fill_note_info(struct elfhdr *elf, int phdrs,
 			  struct elf_note_info *info,
-			  const kernel_siginfo_t *siginfo, struct pt_regs *regs)
+			  struct coredump_params *cprm)
 {
 	struct core_thread *ct;
 	struct elf_thread_status *ets;
@@ -2061,13 +2076,13 @@ static int fill_note_info(struct elfhdr *elf, int phdrs,
 	list_for_each_entry(ets, &info->thread_list, list) {
 		int sz;
 
-		sz = elf_dump_thread_status(siginfo->si_signo, ets);
+		sz = elf_dump_thread_status(cprm->siginfo->si_signo, ets);
 		info->thread_status_size += sz;
 	}
 	/* now collect the dump for the current */
 	memset(info->prstatus, 0, sizeof(*info->prstatus));
-	fill_prstatus(&info->prstatus->common, current, siginfo->si_signo);
-	elf_core_copy_regs(&info->prstatus->pr_reg, regs);
+	fill_prstatus(&info->prstatus->common, current, cprm->siginfo->si_signo);
+	elf_core_copy_regs(&info->prstatus->pr_reg, cprm->regs);
 
 	/* Set up header */
 	fill_elf_header(elf, phdrs, ELF_ARCH, ELF_CORE_EFLAGS);
@@ -2083,18 +2098,18 @@ static int fill_note_info(struct elfhdr *elf, int phdrs,
 	fill_note(info->notes + 1, "CORE", NT_PRPSINFO,
 		  sizeof(*info->psinfo), info->psinfo);
 
-	fill_siginfo_note(info->notes + 2, &info->csigdata, siginfo);
+	fill_siginfo_note(info->notes + 2, &info->csigdata, cprm->siginfo);
 	fill_auxv_note(info->notes + 3, current->mm);
 	info->numnote = 4;
 
-	if (fill_files_note(info->notes + info->numnote) == 0) {
+	if (fill_files_note(info->notes + info->numnote, cprm) == 0) {
 		info->notes_files = info->notes + info->numnote;
 		info->numnote++;
 	}
 
 	/* Try to dump the FPU. */
-	info->prstatus->pr_fpvalid = elf_core_copy_task_fpregs(current, regs,
-							       info->fpu);
+	info->prstatus->pr_fpvalid =
+		elf_core_copy_task_fpregs(current, cprm->regs, info->fpu);
 	if (info->prstatus->pr_fpvalid)
 		fill_note(info->notes + info->numnote++,
 			  "CORE", NT_PRFPREG, sizeof(*info->fpu), info->fpu);
@@ -2180,8 +2195,7 @@ static void fill_extnum_info(struct elfhdr *elf, struct elf_shdr *shdr4extnum,
 static int elf_core_dump(struct coredump_params *cprm)
 {
 	int has_dumped = 0;
-	int vma_count, segs, i;
-	size_t vma_data_size;
+	int segs, i;
 	struct elfhdr elf;
 	loff_t offset = 0, dataoff;
 	struct elf_note_info info = { };
@@ -2189,16 +2203,12 @@ static int elf_core_dump(struct coredump_params *cprm)
 	struct elf_shdr *shdr4extnum = NULL;
 	Elf_Half e_phnum;
 	elf_addr_t e_shoff;
-	struct core_vma_metadata *vma_meta;
-
-	if (dump_vma_snapshot(cprm, &vma_count, &vma_meta, &vma_data_size))
-		return 0;
 
 	/*
 	 * The number of segs are recored into ELF header as 16bit value.
 	 * Please check DEFAULT_MAX_MAP_COUNT definition when you modify here.
 	 */
-	segs = vma_count + elf_core_extra_phdrs();
+	segs = cprm->vma_count + elf_core_extra_phdrs();
 
 	/* for notes section */
 	segs++;
@@ -2212,7 +2222,7 @@ static int elf_core_dump(struct coredump_params *cprm)
 	 * Collect all the non-memory information about the process for the
 	 * notes.  This also sets up the file header.
 	 */
-	if (!fill_note_info(&elf, e_phnum, &info, cprm->siginfo, cprm->regs))
+	if (!fill_note_info(&elf, e_phnum, &info, cprm))
 		goto end_coredump;
 
 	has_dumped = 1;
@@ -2237,7 +2247,7 @@ static int elf_core_dump(struct coredump_params *cprm)
 
 	dataoff = offset = roundup(offset, ELF_EXEC_PAGESIZE);
 
-	offset += vma_data_size;
+	offset += cprm->vma_data_size;
 	offset += elf_core_extra_data_size();
 	e_shoff = offset;
 
@@ -2257,8 +2267,8 @@ static int elf_core_dump(struct coredump_params *cprm)
 		goto end_coredump;
 
 	/* Write program headers for segments dump */
-	for (i = 0; i < vma_count; i++) {
-		struct core_vma_metadata *meta = vma_meta + i;
+	for (i = 0; i < cprm->vma_count; i++) {
+		struct core_vma_metadata *meta = cprm->vma_meta + i;
 		struct elf_phdr phdr;
 
 		phdr.p_type = PT_LOAD;
@@ -2295,8 +2305,8 @@ static int elf_core_dump(struct coredump_params *cprm)
 	/* Align to page */
 	dump_skip_to(cprm, dataoff);
 
-	for (i = 0; i < vma_count; i++) {
-		struct core_vma_metadata *meta = vma_meta + i;
+	for (i = 0; i < cprm->vma_count; i++) {
+		struct core_vma_metadata *meta = cprm->vma_meta + i;
 
 		if (!dump_user_range(cprm, meta->start, meta->dump_size))
 			goto end_coredump;
@@ -2313,7 +2323,6 @@ static int elf_core_dump(struct coredump_params *cprm)
 end_coredump:
 	free_note_info(&info);
 	kfree(shdr4extnum);
-	kvfree(vma_meta);
 	kfree(phdr4note);
 	return has_dumped;
 }
@@ -2335,3 +2344,7 @@ static void __exit exit_elf_binfmt(void)
 core_initcall(init_elf_binfmt);
 module_exit(exit_elf_binfmt);
 MODULE_LICENSE("GPL");
+
+#ifdef CONFIG_BINFMT_ELF_KUNIT_TEST
+#include "binfmt_elf_test.c"
+#endif

fs/binfmt_elf_fdpic.c

@@ -83,8 +83,8 @@ static struct linux_binfmt elf_fdpic_format = {
 	.load_binary	= load_elf_fdpic_binary,
 #ifdef CONFIG_ELF_CORE
 	.core_dump	= elf_fdpic_core_dump,
-#endif
 	.min_coredump	= ELF_EXEC_PAGESIZE,
+#endif
 };
 
 static int __init init_elf_fdpic_binfmt(void)
@@ -1465,7 +1465,7 @@ static bool elf_fdpic_dump_segments(struct coredump_params *cprm,
 static int elf_fdpic_core_dump(struct coredump_params *cprm)
 {
 	int has_dumped = 0;
-	int vma_count, segs;
+	int segs;
 	int i;
 	struct elfhdr *elf = NULL;
 	loff_t offset = 0, dataoff;
@@ -1480,8 +1480,6 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
 	elf_addr_t e_shoff;
 	struct core_thread *ct;
 	struct elf_thread_status *tmp;
-	struct core_vma_metadata *vma_meta = NULL;
-	size_t vma_data_size;
 
 	/* alloc memory for large data structures: too large to be on stack */
 	elf = kmalloc(sizeof(*elf), GFP_KERNEL);
@@ -1491,9 +1489,6 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
 	if (!psinfo)
 		goto end_coredump;
 
-	if (dump_vma_snapshot(cprm, &vma_count, &vma_meta, &vma_data_size))
-		goto end_coredump;
-
 	for (ct = current->signal->core_state->dumper.next;
 					ct; ct = ct->next) {
 		tmp = elf_dump_thread_status(cprm->siginfo->si_signo,
@@ -1513,7 +1508,7 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
 	tmp->next = thread_list;
 	thread_list = tmp;
 
-	segs = vma_count + elf_core_extra_phdrs();
+	segs = cprm->vma_count + elf_core_extra_phdrs();
 
 	/* for notes section */
 	segs++;
@@ -1558,7 +1553,7 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
 	/* Page-align dumped data */
 	dataoff = offset = roundup(offset, ELF_EXEC_PAGESIZE);
 
-	offset += vma_data_size;
+	offset += cprm->vma_data_size;
 	offset += elf_core_extra_data_size();
 	e_shoff = offset;
 
@@ -1578,8 +1573,8 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
 		goto end_coredump;
 
 	/* write program headers for segments dump */
-	for (i = 0; i < vma_count; i++) {
-		struct core_vma_metadata *meta = vma_meta + i;
+	for (i = 0; i < cprm->vma_count; i++) {
+		struct core_vma_metadata *meta = cprm->vma_meta + i;
 		struct elf_phdr phdr;
 		size_t sz;
 
@@ -1628,7 +1623,7 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
 
 	dump_skip_to(cprm, dataoff);
 
-	if (!elf_fdpic_dump_segments(cprm, vma_meta, vma_count))
+	if (!elf_fdpic_dump_segments(cprm, cprm->vma_meta, cprm->vma_count))
 		goto end_coredump;
 
 	if (!elf_core_write_extra_data(cprm))
@@ -1652,7 +1647,6 @@ static int elf_fdpic_core_dump(struct coredump_params *cprm)
 		thread_list = thread_list->next;
 		kfree(tmp);
 	}
-	kvfree(vma_meta);
 	kfree(phdr4note);
 	kfree(elf);
 	kfree(psinfo);

fs/binfmt_elf_test.c

+// SPDX-License-Identifier: GPL-2.0-only
+#include <kunit/test.h>
+
+static void total_mapping_size_test(struct kunit *test)
+{
+	struct elf_phdr empty[] = {
+		{ .p_type = PT_LOAD, .p_vaddr = 0, .p_memsz = 0, },
+		{ .p_type = PT_INTERP, .p_vaddr = 10, .p_memsz = 999999, },
+	};
+	/*
+	 * readelf -lW /bin/mount | grep '^  .*0x0' | awk '{print "\t\t{ .p_type = PT_" \
+	 *				$1 ", .p_vaddr = " $3 ", .p_memsz = " $6 ", },"}'
+	 */
+	struct elf_phdr mount[] = {
+		{ .p_type = PT_PHDR, .p_vaddr = 0x00000040, .p_memsz = 0x0002d8, },
+		{ .p_type = PT_INTERP, .p_vaddr = 0x00000318, .p_memsz = 0x00001c, },
+		{ .p_type = PT_LOAD, .p_vaddr = 0x00000000, .p_memsz = 0x0033a8, },
+		{ .p_type = PT_LOAD, .p_vaddr = 0x00004000, .p_memsz = 0x005c91, },
+		{ .p_type = PT_LOAD, .p_vaddr = 0x0000a000, .p_memsz = 0x0022f8, },
+		{ .p_type = PT_LOAD, .p_vaddr = 0x0000d330, .p_memsz = 0x000d40, },
+		{ .p_type = PT_DYNAMIC, .p_vaddr = 0x0000d928, .p_memsz = 0x000200, },
+		{ .p_type = PT_NOTE, .p_vaddr = 0x00000338, .p_memsz = 0x000030, },
+		{ .p_type = PT_NOTE, .p_vaddr = 0x00000368, .p_memsz = 0x000044, },
+		{ .p_type = PT_GNU_PROPERTY, .p_vaddr = 0x00000338, .p_memsz = 0x000030, },
+		{ .p_type = PT_GNU_EH_FRAME, .p_vaddr = 0x0000b490, .p_memsz = 0x0001ec, },
+		{ .p_type = PT_GNU_STACK, .p_vaddr = 0x00000000, .p_memsz = 0x000000, },
+		{ .p_type = PT_GNU_RELRO, .p_vaddr = 0x0000d330, .p_memsz = 0x000cd0, },
+	};
+	size_t mount_size = 0xE070;
+	/* https://lore.kernel.org/linux-fsdevel/YfF18Dy85mCntXrx@fractal.localdomain */
+	struct elf_phdr unordered[] = {
+		{ .p_type = PT_LOAD, .p_vaddr = 0x00000000, .p_memsz = 0x0033a8, },
+		{ .p_type = PT_LOAD, .p_vaddr = 0x0000d330, .p_memsz = 0x000d40, },
+		{ .p_type = PT_LOAD, .p_vaddr = 0x00004000, .p_memsz = 0x005c91, },
+		{ .p_type = PT_LOAD, .p_vaddr = 0x0000a000, .p_memsz = 0x0022f8, },
+	};
+
+	/* No headers, no size. */
+	KUNIT_EXPECT_EQ(test, total_mapping_size(NULL, 0), 0);
+	KUNIT_EXPECT_EQ(test, total_mapping_size(empty, 0), 0);
+	/* Empty headers, no size. */
+	KUNIT_EXPECT_EQ(test, total_mapping_size(empty, 1), 0);
+	/* No PT_LOAD headers, no size. */
+	KUNIT_EXPECT_EQ(test, total_mapping_size(&empty[1], 1), 0);
+	/* Empty PT_LOAD and non-PT_LOAD headers, no size. */
+	KUNIT_EXPECT_EQ(test, total_mapping_size(empty, 2), 0);
+
+	/* Normal set of PT_LOADS, and expected size. */
+	KUNIT_EXPECT_EQ(test, total_mapping_size(mount, ARRAY_SIZE(mount)), mount_size);
+	/* Unordered PT_LOADs result in same size. */
+	KUNIT_EXPECT_EQ(test, total_mapping_size(unordered, ARRAY_SIZE(unordered)), mount_size);
+}
+
+static struct kunit_case binfmt_elf_test_cases[] = {
+	KUNIT_CASE(total_mapping_size_test),
+	{},
+};
+
+static struct kunit_suite binfmt_elf_test_suite = {
+	.name = KBUILD_MODNAME,
+	.test_cases = binfmt_elf_test_cases,
+};
+
+kunit_test_suite(binfmt_elf_test_suite);

fs/binfmt_flat.c

@@ -37,6 +37,7 @@
 #include <linux/flat.h>
 #include <linux/uaccess.h>
 #include <linux/vmalloc.h>
+#include <linux/coredump.h>
 
 #include <asm/byteorder.h>
 #include <asm/unaligned.h>
@@ -97,13 +98,17 @@ static int load_flat_shared_library(int id, struct lib_info *p);
 #endif
 
 static int load_flat_binary(struct linux_binprm *);
+#ifdef CONFIG_COREDUMP
 static int flat_core_dump(struct coredump_params *cprm);
+#endif
 
 static struct linux_binfmt flat_format = {
 	.module		= THIS_MODULE,
 	.load_binary	= load_flat_binary,
+#ifdef CONFIG_COREDUMP
 	.core_dump	= flat_core_dump,
 	.min_coredump	= PAGE_SIZE
+#endif
 };
 
 /****************************************************************************/
@@ -112,12 +117,14 @@ static struct linux_binfmt flat_format = {
  * Currently only a stub-function.
  */
 
+#ifdef CONFIG_COREDUMP
 static int flat_core_dump(struct coredump_params *cprm)
 {
 	pr_warn("Process %s:%d received signr %d and should have core dumped\n",
 		current->comm, current->pid, cprm->siginfo->si_signo);
 	return 1;
 }
+#endif
 
 /****************************************************************************/
 /*

fs/compat_binfmt_elf.c

@@ -135,6 +135,8 @@
 #define elf_format		compat_elf_format
 #define init_elf_binfmt		init_compat_elf_binfmt
 #define exit_elf_binfmt		exit_compat_elf_binfmt
+#define binfmt_elf_test_cases	compat_binfmt_elf_test_cases
+#define binfmt_elf_test_suite	compat_binfmt_elf_test_suite
 
 /*
  * We share all the actual code with the native (64-bit) version.

fs/coredump.c

@@ -42,6 +42,7 @@
 #include <linux/path.h>
 #include <linux/timekeeping.h>
 #include <linux/sysctl.h>
+#include <linux/elf.h>
 
 #include <linux/uaccess.h>
 #include <asm/mmu_context.h>
@@ -53,6 +54,9 @@
 
 #include <trace/events/sched.h>
 
+static bool dump_vma_snapshot(struct coredump_params *cprm);
+static void free_vma_snapshot(struct coredump_params *cprm);
+
 static int core_uses_pid;
 static unsigned int core_pipe_limit;
 static char core_pattern[CORENAME_MAX_SIZE] = "core";
@@ -531,6 +535,7 @@ void do_coredump(const kernel_siginfo_t *siginfo)
 		 * by any locks.
 		 */
 		.mm_flags = mm->flags,
+		.vma_meta = NULL,
 	};
 
 	audit_core_dumps(siginfo->si_signo);
@@ -745,6 +750,9 @@ void do_coredump(const kernel_siginfo_t *siginfo)
 			pr_info("Core dump to |%s disabled\n", cn.corename);
 			goto close_fail;
 		}
+		if (!dump_vma_snapshot(&cprm))
+			goto close_fail;
+
 		file_start_write(cprm.file);
 		core_dumped = binfmt->core_dump(&cprm);
 		/*
@@ -758,6 +766,7 @@ void do_coredump(const kernel_siginfo_t *siginfo)
 			dump_emit(&cprm, "", 1);
 		}
 		file_end_write(cprm.file);
+		free_vma_snapshot(&cprm);
 	}
 	if (ispipe && core_pipe_limit)
 		wait_for_dump_helpers(cprm.file);
@@ -980,6 +989,8 @@ static bool always_dump_vma(struct vm_area_struct *vma)
 	return false;
 }
 
+#define DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER 1
+
 /*
  * Decide how much of @vma's contents should be included in a core dump.
  */
@@ -1039,9 +1050,20 @@ static unsigned long vma_dump_size(struct vm_area_struct *vma,
 	 * dump the first page to aid in determining what was mapped here.
 	 */
 	if (FILTER(ELF_HEADERS) &&
-	    vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ) &&
-	    (READ_ONCE(file_inode(vma->vm_file)->i_mode) & 0111) != 0)
-		return PAGE_SIZE;
+	    vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ)) {
+		if ((READ_ONCE(file_inode(vma->vm_file)->i_mode) & 0111) != 0)
+			return PAGE_SIZE;
+
+		/*
+		 * ELF libraries aren't always executable.
+		 * We'll want to check whether the mapping starts with the ELF
+		 * magic, but not now - we're holding the mmap lock,
+		 * so copy_from_user() doesn't work here.
+		 * Use a placeholder instead, and fix it up later in
+		 * dump_vma_snapshot().
+		 */
+		return DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER;
+	}
 
 #undef	FILTER
 
@@ -1078,18 +1100,29 @@ static struct vm_area_struct *next_vma(struct vm_area_struct *this_vma,
 	return gate_vma;
 }
 
+static void free_vma_snapshot(struct coredump_params *cprm)
+{
+	if (cprm->vma_meta) {
+		int i;
+		for (i = 0; i < cprm->vma_count; i++) {
+			struct file *file = cprm->vma_meta[i].file;
+			if (file)
+				fput(file);
+		}
+		kvfree(cprm->vma_meta);
+		cprm->vma_meta = NULL;
+	}
+}
+
 /*
  * Under the mmap_lock, take a snapshot of relevant information about the task's
  * VMAs.
  */
-int dump_vma_snapshot(struct coredump_params *cprm, int *vma_count,
-		      struct core_vma_metadata **vma_meta,
-		      size_t *vma_data_size_ptr)
+static bool dump_vma_snapshot(struct coredump_params *cprm)
 {
 	struct vm_area_struct *vma, *gate_vma;
 	struct mm_struct *mm = current->mm;
 	int i;
-	size_t vma_data_size = 0;
 
 	/*
 	 * Once the stack expansion code is fixed to not change VMA bounds
@@ -1097,36 +1130,51 @@ int dump_vma_snapshot(struct coredump_params *cprm, int *vma_count,
 	 * mmap_lock in read mode.
 	 */
 	if (mmap_write_lock_killable(mm))
-		return -EINTR;
+		return false;
 
+	cprm->vma_data_size = 0;
 	gate_vma = get_gate_vma(mm);
-	*vma_count = mm->map_count + (gate_vma ? 1 : 0);
+	cprm->vma_count = mm->map_count + (gate_vma ? 1 : 0);
 
-	*vma_meta = kvmalloc_array(*vma_count, sizeof(**vma_meta), GFP_KERNEL);
-	if (!*vma_meta) {
+	cprm->vma_meta = kvmalloc_array(cprm->vma_count, sizeof(*cprm->vma_meta), GFP_KERNEL);
+	if (!cprm->vma_meta) {
 		mmap_write_unlock(mm);
-		return -ENOMEM;
+		return false;
 	}
 
 	for (i = 0, vma = first_vma(current, gate_vma); vma != NULL;
 			vma = next_vma(vma, gate_vma), i++) {
-		struct core_vma_metadata *m = (*vma_meta) + i;
+		struct core_vma_metadata *m = cprm->vma_meta + i;
 
 		m->start = vma->vm_start;
 		m->end = vma->vm_end;
 		m->flags = vma->vm_flags;
 		m->dump_size = vma_dump_size(vma, cprm->mm_flags);
+		m->pgoff = vma->vm_pgoff;
 
-		vma_data_size += m->dump_size;
+		m->file = vma->vm_file;
+		if (m->file)
+			get_file(m->file);
 	}
 
 	mmap_write_unlock(mm);
 
-	if (WARN_ON(i != *vma_count)) {
-		kvfree(*vma_meta);
-		return -EFAULT;
+	for (i = 0; i < cprm->vma_count; i++) {
+		struct core_vma_metadata *m = cprm->vma_meta + i;
+
+		if (m->dump_size == DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER) {
+			char elfmag[SELFMAG];
+
+			if (copy_from_user(elfmag, (void __user *)m->start, SELFMAG) ||
+					memcmp(elfmag, ELFMAG, SELFMAG) != 0) {
+				m->dump_size = 0;
+			} else {
+				m->dump_size = PAGE_SIZE;
+			}
+		}
+
+		cprm->vma_data_size += m->dump_size;
 	}
 
-	*vma_data_size_ptr = vma_data_size;
-	return 0;
+	return true;
 }

fs/exec.c

@@ -118,7 +118,7 @@ bool path_noexec(const struct path *path)
  * Note that a shared library must be both readable and executable due to
  * security reasons.
  *
- * Also note that we take the address to load from from the file itself.
+ * Also note that we take the address to load from the file itself.
  */
 SYSCALL_DEFINE1(uselib, const char __user *, library)
 {
@@ -495,8 +495,14 @@ static int bprm_stack_limits(struct linux_binprm *bprm)
 	 * 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 = (bprm->argc + bprm->envc) * sizeof(void *);
+	ptr_size = (max(bprm->argc, 1) + bprm->envc) * sizeof(void *);
 	if (limit <= ptr_size)
 		return -E2BIG;
 	limit -= ptr_size;
@@ -536,7 +542,7 @@ static int copy_strings(int argc, struct user_arg_ptr argv,
 		if (!valid_arg_len(bprm, len))
 			goto out;
 
-		/* We're going to work our way backwords. */
+		/* We're going to work our way backwards. */
 		pos = bprm->p;
 		str += len;
 		bprm->p -= len;
@@ -1269,7 +1275,7 @@ int begin_new_exec(struct linux_binprm * bprm)
 
 	/*
 	 * Must be called _before_ exec_mmap() as bprm->mm is
-	 * not visibile until then. This also enables the update
+	 * not visible until then. This also enables the update
 	 * to be lockless.
 	 */
 	retval = set_mm_exe_file(bprm->mm, bprm->file);
@@ -1897,6 +1903,9 @@ static int do_execveat_common(int fd, struct filename *filename,
 	}
 
 	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;
@@ -1923,6 +1932,19 @@ static int do_execveat_common(int fd, struct filename *filename,
 	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);
@@ -1951,6 +1973,8 @@ int kernel_execve(const char *kernel_filename,
 	}
 
 	retval = count_strings_kernel(argv);
+	if (WARN_ON_ONCE(retval == 0))
+		retval = -EINVAL;
 	if (retval < 0)
 		goto out_free;
 	bprm->argc = retval;

include/linux/binfmts.h

@@ -8,6 +8,7 @@
 #include <uapi/linux/binfmts.h>
 
 struct filename;
+struct coredump_params;
 
 #define CORENAME_MAX_SIZE 128
 
@@ -77,18 +78,6 @@ struct linux_binprm {
 #define BINPRM_FLAGS_PRESERVE_ARGV0_BIT 3
 #define BINPRM_FLAGS_PRESERVE_ARGV0 (1 << BINPRM_FLAGS_PRESERVE_ARGV0_BIT)
 
-/* Function parameter for binfmt->coredump */
-struct coredump_params {
-	const kernel_siginfo_t *siginfo;
-	struct pt_regs *regs;
-	struct file *file;
-	unsigned long limit;
-	unsigned long mm_flags;
-	loff_t written;
-	loff_t pos;
-	loff_t to_skip;
-};
-
 /*
  * This structure defines the functions that are used to load the binary formats that
  * linux accepts.
@@ -98,8 +87,10 @@ struct linux_binfmt {
 	struct module *module;
 	int (*load_binary)(struct linux_binprm *);
 	int (*load_shlib)(struct file *);
+#ifdef CONFIG_COREDUMP
 	int (*core_dump)(struct coredump_params *cprm);
 	unsigned long min_coredump;	/* minimal dump size */
+#endif
 } __randomize_layout;
 
 extern void __register_binfmt(struct linux_binfmt *fmt, int insert);

include/linux/coredump.h

@@ -12,22 +12,34 @@ struct core_vma_metadata {
 	unsigned long start, end;
 	unsigned long flags;
 	unsigned long dump_size;
+	unsigned long pgoff;
+	struct file   *file;
+};
+
+struct coredump_params {
+	const kernel_siginfo_t *siginfo;
+	struct pt_regs *regs;
+	struct file *file;
+	unsigned long limit;
+	unsigned long mm_flags;
+	loff_t written;
+	loff_t pos;
+	loff_t to_skip;
+	int vma_count;
+	size_t vma_data_size;
+	struct core_vma_metadata *vma_meta;
 };
 
 /*
  * These are the only things you should do on a core-file: use only these
  * functions to write out all the necessary info.
  */
-struct coredump_params;
 extern void dump_skip_to(struct coredump_params *cprm, unsigned long to);
 extern void dump_skip(struct coredump_params *cprm, size_t nr);
 extern int dump_emit(struct coredump_params *cprm, const void *addr, int nr);
 extern int dump_align(struct coredump_params *cprm, int align);
 int dump_user_range(struct coredump_params *cprm, unsigned long start,
 		    unsigned long len);
-int dump_vma_snapshot(struct coredump_params *cprm, int *vma_count,
-		      struct core_vma_metadata **vma_meta,
-		      size_t *vma_data_size_ptr);
 extern void do_coredump(const kernel_siginfo_t *siginfo);
 #else
 static inline void do_coredump(const kernel_siginfo_t *siginfo) {}

include/uapi/linux/elf.h

@@ -35,10 +35,11 @@ typedef __s64	Elf64_Sxword;
 #define PT_HIOS    0x6fffffff      /* OS-specific */
 #define PT_LOPROC  0x70000000
 #define PT_HIPROC  0x7fffffff
-#define PT_GNU_EH_FRAME		0x6474e550
-#define PT_GNU_PROPERTY		0x6474e553
-
+#define PT_GNU_EH_FRAME	(PT_LOOS + 0x474e550)
 #define PT_GNU_STACK	(PT_LOOS + 0x474e551)
+#define PT_GNU_RELRO	(PT_LOOS + 0x474e552)
+#define PT_GNU_PROPERTY	(PT_LOOS + 0x474e553)
+
 
 /* ARM MTE memory tag segment type */
 #define PT_ARM_MEMTAG_MTE	(PT_LOPROC + 0x1)

tools/testing/selftests/exec/Makefile

@@ -10,6 +10,7 @@ TEST_GEN_FILES := execveat.symlink execveat.denatured script subdir
 TEST_FILES := Makefile
 
 TEST_GEN_PROGS += recursion-depth
+TEST_GEN_PROGS += null-argv
 
 EXTRA_CLEAN := $(OUTPUT)/subdir.moved $(OUTPUT)/execveat.moved $(OUTPUT)/xxxxx*	\
 	       $(OUTPUT)/S_I*.test

tools/testing/selftests/exec/null-argv.c

+// SPDX-License-Identifier: GPL-2.0-only
+/* Test that empty argvs are swapped out for a single empty string. */
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+#include "../kselftest.h"
+
+#define FORK(exec)				\
+do {						\
+	pid = fork();				\
+	if (pid == 0) {				\
+		/* Child */			\
+		exec; /* Some kind of exec */	\
+		perror("# " #exec);		\
+		return 1;			\
+	}					\
+	check_result(pid, #exec);		\
+} while (0)
+
+void check_result(pid_t pid, const char *msg)
+{
+	int wstatus;
+
+	if (pid == (pid_t)-1) {
+		perror("# fork");
+		ksft_test_result_fail("fork failed: %s\n", msg);
+		return;
+	}
+	if (waitpid(pid, &wstatus, 0) < 0) {
+		perror("# waitpid");
+		ksft_test_result_fail("waitpid failed: %s\n", msg);
+		return;
+	}
+	if (!WIFEXITED(wstatus)) {
+		ksft_test_result_fail("child did not exit: %s\n", msg);
+		return;
+	}
+	if (WEXITSTATUS(wstatus) != 0) {
+		ksft_test_result_fail("non-zero exit: %s\n", msg);
+		return;
+	}
+	ksft_test_result_pass("%s\n", msg);
+}
+
+int main(int argc, char *argv[], char *envp[])
+{
+	pid_t pid;
+	static char * const args[] = { NULL };
+	static char * const str[] = { "", NULL };
+
+	/* argc counting checks */
+	if (argc < 1) {
+		fprintf(stderr, "# FAIL: saw argc == 0 (old kernel?)\n");
+		return 1;
+	}
+	if (argc != 1) {
+		fprintf(stderr, "# FAIL: unknown argc (%d)\n", argc);
+		return 1;
+	}
+	if (argv[0][0] == '\0') {
+		/* Good, we found a NULL terminated string at argv[0]! */
+		return 0;
+	}
+
+	/* Test runner. */
+	ksft_print_header();
+	ksft_set_plan(5);
+
+	FORK(execve(argv[0], str, NULL));
+	FORK(execve(argv[0], NULL, NULL));
+	FORK(execve(argv[0], NULL, envp));
+	FORK(execve(argv[0], args, NULL));
+	FORK(execve(argv[0], args, envp));
+
+	ksft_exit(ksft_cnt.ksft_pass == ksft_plan);
+}