mm: variable length argument support

Remove the arg+env limit of MAX_ARG_PAGES by copying the strings directly from
the old mm into the new mm.

We create the new mm before the binfmt code runs, and place the new stack at
the very top of the address space.  Once the binfmt code runs and figures out
where the stack should be, we move it downwards.

It is a bit peculiar in that we have one task with two mm's, one of which is
inactive.

[a.p.zijlstra@chello.nl: limit stack size]
Signed-off-by: Ollie Wild <aaw@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: <linux-arch@vger.kernel.org>
Cc: Hugh Dickins <hugh@veritas.com>
[bunk@stusta.de: unexport bprm_mm_init]
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/ia64/ia32/binfmt_elf32.c

@@ -195,62 +195,27 @@ ia64_elf32_init (struct pt_regs *regs)
 	ia32_load_state(current);
 }
 
+/*
+ * Undo the override of setup_arg_pages() without this ia32_setup_arg_pages()
+ * will suffer infinite self recursion.
+ */
+#undef setup_arg_pages
+
 int
 ia32_setup_arg_pages (struct linux_binprm *bprm, int executable_stack)
 {
-	unsigned long stack_base;
-	struct vm_area_struct *mpnt;
-	struct mm_struct *mm = current->mm;
-	int i, ret;
-
-	stack_base = IA32_STACK_TOP - MAX_ARG_PAGES*PAGE_SIZE;
-	mm->arg_start = bprm->p + stack_base;
-
-	bprm->p += stack_base;
-	if (bprm->loader)
-		bprm->loader += stack_base;
-	bprm->exec += stack_base;
-
-	mpnt = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
-	if (!mpnt)
-		return -ENOMEM;
-
-	down_write(&current->mm->mmap_sem);
-	{
-		mpnt->vm_mm = current->mm;
-		mpnt->vm_start = PAGE_MASK & (unsigned long) bprm->p;
-		mpnt->vm_end = IA32_STACK_TOP;
-		if (executable_stack == EXSTACK_ENABLE_X)
-			mpnt->vm_flags = VM_STACK_FLAGS |  VM_EXEC;
-		else if (executable_stack == EXSTACK_DISABLE_X)
-			mpnt->vm_flags = VM_STACK_FLAGS & ~VM_EXEC;
-		else
-			mpnt->vm_flags = VM_STACK_FLAGS;
-		mpnt->vm_page_prot = (mpnt->vm_flags & VM_EXEC)?
-					PAGE_COPY_EXEC: PAGE_COPY;
-		if ((ret = insert_vm_struct(current->mm, mpnt))) {
-			up_write(&current->mm->mmap_sem);
-			kmem_cache_free(vm_area_cachep, mpnt);
-			return ret;
-		}
-		current->mm->stack_vm = current->mm->total_vm = vma_pages(mpnt);
+	int ret;
+
+	ret = setup_arg_pages(bprm, IA32_STACK_TOP, executable_stack);
+	if (!ret) {
+		/*
+		 * Can't do it in ia64_elf32_init(). Needs to be done before
+		 * calls to elf32_map()
+		 */
+		current->thread.ppl = ia32_init_pp_list();
 	}
 
-	for (i = 0 ; i < MAX_ARG_PAGES ; i++) {
-		struct page *page = bprm->page[i];
-		if (page) {
-			bprm->page[i] = NULL;
-			install_arg_page(mpnt, page, stack_base);
-		}
-		stack_base += PAGE_SIZE;
-	}
-	up_write(&current->mm->mmap_sem);
-
-	/* Can't do it in ia64_elf32_init(). Needs to be done before calls to
-	   elf32_map() */
-	current->thread.ppl = ia32_init_pp_list();
-
-	return 0;
+	return ret;
 }
 
 static void

arch/x86_64/ia32/ia32_aout.c

@@ -404,7 +404,7 @@ static int load_aout_binary(struct linux_binprm * bprm, struct pt_regs * regs)
 
 	set_brk(current->mm->start_brk, current->mm->brk);
 
-	retval = ia32_setup_arg_pages(bprm, IA32_STACK_TOP, EXSTACK_DEFAULT);
+	retval = setup_arg_pages(bprm, IA32_STACK_TOP, EXSTACK_DEFAULT);
 	if (retval < 0) { 
 		/* Someone check-me: is this error path enough? */ 
 		send_sig(SIGKILL, current, 0); 

arch/x86_64/ia32/ia32_binfmt.c

@@ -232,9 +232,6 @@ do {							\
 #define load_elf_binary load_elf32_binary
 
 #define ELF_PLAT_INIT(r, load_addr)	elf32_init(r)
-#define setup_arg_pages(bprm, stack_top, exec_stack) \
-	ia32_setup_arg_pages(bprm, stack_top, exec_stack)
-int ia32_setup_arg_pages(struct linux_binprm *bprm, unsigned long stack_top, int executable_stack);
 
 #undef start_thread
 #define start_thread(regs,new_rip,new_rsp) do { \
@@ -286,61 +283,6 @@ static void elf32_init(struct pt_regs *regs)
 	me->thread.es = __USER_DS;
 }
 
-int ia32_setup_arg_pages(struct linux_binprm *bprm, unsigned long stack_top,
-			 int executable_stack)
-{
-	unsigned long stack_base;
-	struct vm_area_struct *mpnt;
-	struct mm_struct *mm = current->mm;
-	int i, ret;
-
-	stack_base = stack_top - MAX_ARG_PAGES * PAGE_SIZE;
-	mm->arg_start = bprm->p + stack_base;
-
-	bprm->p += stack_base;
-	if (bprm->loader)
-		bprm->loader += stack_base;
-	bprm->exec += stack_base;
-
-	mpnt = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
-	if (!mpnt) 
-		return -ENOMEM; 
-
-	down_write(&mm->mmap_sem);
-	{
-		mpnt->vm_mm = mm;
-		mpnt->vm_start = PAGE_MASK & (unsigned long) bprm->p;
-		mpnt->vm_end = stack_top;
-		if (executable_stack == EXSTACK_ENABLE_X)
-			mpnt->vm_flags = VM_STACK_FLAGS |  VM_EXEC;
-		else if (executable_stack == EXSTACK_DISABLE_X)
-			mpnt->vm_flags = VM_STACK_FLAGS & ~VM_EXEC;
-		else
-			mpnt->vm_flags = VM_STACK_FLAGS;
- 		mpnt->vm_page_prot = (mpnt->vm_flags & VM_EXEC) ? 
- 			PAGE_COPY_EXEC : PAGE_COPY;
-		if ((ret = insert_vm_struct(mm, mpnt))) {
-			up_write(&mm->mmap_sem);
-			kmem_cache_free(vm_area_cachep, mpnt);
-			return ret;
-		}
-		mm->stack_vm = mm->total_vm = vma_pages(mpnt);
-	} 
-
-	for (i = 0 ; i < MAX_ARG_PAGES ; i++) {
-		struct page *page = bprm->page[i];
-		if (page) {
-			bprm->page[i] = NULL;
-			install_arg_page(mpnt, page, stack_base);
-		}
-		stack_base += PAGE_SIZE;
-	}
-	up_write(&mm->mmap_sem);
-
-	return 0;
-}
-EXPORT_SYMBOL(ia32_setup_arg_pages);
-
 #ifdef CONFIG_SYSCTL
 /* Register vsyscall32 into the ABI table */
 #include <linux/sysctl.h>

fs/binfmt_elf.c

@@ -148,6 +148,7 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec,
 	elf_addr_t *elf_info;
 	int ei_index = 0;
 	struct task_struct *tsk = current;
+	struct vm_area_struct *vma;
 
 	/*
 	 * If this architecture has a platform capability string, copy it
@@ -234,6 +235,15 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec,
 	sp = (elf_addr_t __user *)bprm->p;
 #endif
 
+
+	/*
+	 * Grow the stack manually; some architectures have a limit on how
+	 * far ahead a user-space access may be in order to grow the stack.
+	 */
+	vma = find_extend_vma(current->mm, bprm->p);
+	if (!vma)
+		return -EFAULT;
+
 	/* Now, let's put argc (and argv, envp if appropriate) on the stack */
 	if (__put_user(argc, sp++))
 		return -EFAULT;
@@ -254,8 +264,8 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec,
 		size_t len;
 		if (__put_user((elf_addr_t)p, argv++))
 			return -EFAULT;
-		len = strnlen_user((void __user *)p, PAGE_SIZE*MAX_ARG_PAGES);
-		if (!len || len > PAGE_SIZE*MAX_ARG_PAGES)
+		len = strnlen_user((void __user *)p, MAX_ARG_STRLEN);
+		if (!len || len > MAX_ARG_STRLEN)
 			return 0;
 		p += len;
 	}
@@ -266,8 +276,8 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec,
 		size_t len;
 		if (__put_user((elf_addr_t)p, envp++))
 			return -EFAULT;
-		len = strnlen_user((void __user *)p, PAGE_SIZE*MAX_ARG_PAGES);
-		if (!len || len > PAGE_SIZE*MAX_ARG_PAGES)
+		len = strnlen_user((void __user *)p, MAX_ARG_STRLEN);
+		if (!len || len > MAX_ARG_STRLEN)
 			return 0;
 		p += len;
 	}
@@ -826,10 +836,6 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs)
 	}
 
 	/* OK, This is the point of no return */
-	current->mm->start_data = 0;
-	current->mm->end_data = 0;
-	current->mm->end_code = 0;
-	current->mm->mmap = NULL;
 	current->flags &= ~PF_FORKNOEXEC;
 	current->mm->def_flags = def_flags;
 
@@ -1051,9 +1057,13 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs)
 
 	compute_creds(bprm);
 	current->flags &= ~PF_FORKNOEXEC;
-	create_elf_tables(bprm, &loc->elf_ex,
+	retval = create_elf_tables(bprm, &loc->elf_ex,
 			  (interpreter_type == INTERPRETER_AOUT),
 			  load_addr, interp_load_addr);
+	if (retval < 0) {
+		send_sig(SIGKILL, current, 0);
+		goto out;
+	}
 	/* N.B. passed_fileno might not be initialized? */
 	if (interpreter_type == INTERPRETER_AOUT)
 		current->mm->arg_start += strlen(passed_fileno) + 1;

fs/binfmt_elf_fdpic.c

@@ -621,8 +621,8 @@ static int create_elf_fdpic_tables(struct linux_binprm *bprm,
 	p = (char __user *) current->mm->arg_start;
 	for (loop = bprm->argc; loop > 0; loop--) {
 		__put_user((elf_caddr_t) p, argv++);
-		len = strnlen_user(p, PAGE_SIZE * MAX_ARG_PAGES);
-		if (!len || len > PAGE_SIZE * MAX_ARG_PAGES)
+		len = strnlen_user(p, MAX_ARG_STRLEN);
+		if (!len || len > MAX_ARG_STRLEN)
 			return -EINVAL;
 		p += len;
 	}
@@ -633,8 +633,8 @@ static int create_elf_fdpic_tables(struct linux_binprm *bprm,
 	current->mm->env_start = (unsigned long) p;
 	for (loop = bprm->envc; loop > 0; loop--) {
 		__put_user((elf_caddr_t)(unsigned long) p, envp++);
-		len = strnlen_user(p, PAGE_SIZE * MAX_ARG_PAGES);
-		if (!len || len > PAGE_SIZE * MAX_ARG_PAGES)
+		len = strnlen_user(p, MAX_ARG_STRLEN);
+		if (!len || len > MAX_ARG_STRLEN)
 			return -EINVAL;
 		p += len;
 	}

fs/binfmt_misc.c

@@ -126,7 +126,9 @@ static int load_misc_binary(struct linux_binprm *bprm, struct pt_regs *regs)
 		goto _ret;
 
 	if (!(fmt->flags & MISC_FMT_PRESERVE_ARGV0)) {
-		remove_arg_zero(bprm);
+		retval = remove_arg_zero(bprm);
+		if (retval)
+			goto _ret;
 	}
 
 	if (fmt->flags & MISC_FMT_OPEN_BINARY) {

fs/binfmt_script.c

@@ -67,7 +67,9 @@ static int load_script(struct linux_binprm *bprm,struct pt_regs *regs)
 	 * This is done in reverse order, because of how the
 	 * user environment and arguments are stored.
 	 */
-	remove_arg_zero(bprm);
+	retval = remove_arg_zero(bprm);
+	if (retval)
+		return retval;
 	retval = copy_strings_kernel(1, &bprm->interp, bprm);
 	if (retval < 0) return retval; 
 	bprm->argc++;