binfmt_aout.c revision 4589ff7c
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 *  linux/fs/binfmt_aout.c
4 *
5 *  Copyright (C) 1991, 1992, 1996  Linus Torvalds
6 */
7
8#include <linux/module.h>
9
10#include <linux/time.h>
11#include <linux/kernel.h>
12#include <linux/mm.h>
13#include <linux/mman.h>
14#include <linux/a.out.h>
15#include <linux/errno.h>
16#include <linux/signal.h>
17#include <linux/string.h>
18#include <linux/fs.h>
19#include <linux/file.h>
20#include <linux/stat.h>
21#include <linux/fcntl.h>
22#include <linux/ptrace.h>
23#include <linux/user.h>
24#include <linux/binfmts.h>
25#include <linux/personality.h>
26#include <linux/init.h>
27#include <linux/coredump.h>
28#include <linux/slab.h>
29#include <linux/sched/task_stack.h>
30
31#include <linux/uaccess.h>
32#include <asm/cacheflush.h>
33
34static int load_aout_binary(struct linux_binprm *);
35static int load_aout_library(struct file*);
36
37static struct linux_binfmt aout_format = {
38	.module		= THIS_MODULE,
39	.load_binary	= load_aout_binary,
40	.load_shlib	= load_aout_library,
41};
42
43#define BAD_ADDR(x)	((unsigned long)(x) >= TASK_SIZE)
44
45static int set_brk(unsigned long start, unsigned long end)
46{
47	start = PAGE_ALIGN(start);
48	end = PAGE_ALIGN(end);
49	if (end > start)
50		return vm_brk(start, end - start);
51	return 0;
52}
53
54/*
55 * create_aout_tables() parses the env- and arg-strings in new user
56 * memory and creates the pointer tables from them, and puts their
57 * addresses on the "stack", returning the new stack pointer value.
58 */
59static unsigned long __user *create_aout_tables(char __user *p, struct linux_binprm * bprm)
60{
61	char __user * __user *argv;
62	char __user * __user *envp;
63	unsigned long __user *sp;
64	int argc = bprm->argc;
65	int envc = bprm->envc;
66
67	sp = (void __user *)((-(unsigned long)sizeof(char *)) & (unsigned long) p);
68#ifdef __alpha__
69/* whee.. test-programs are so much fun. */
70	put_user(0, --sp);
71	put_user(0, --sp);
72	if (bprm->loader) {
73		put_user(0, --sp);
74		put_user(1003, --sp);
75		put_user(bprm->loader, --sp);
76		put_user(1002, --sp);
77	}
78	put_user(bprm->exec, --sp);
79	put_user(1001, --sp);
80#endif
81	sp -= envc+1;
82	envp = (char __user * __user *) sp;
83	sp -= argc+1;
84	argv = (char __user * __user *) sp;
85#ifndef __alpha__
86	put_user((unsigned long) envp,--sp);
87	put_user((unsigned long) argv,--sp);
88#endif
89	put_user(argc,--sp);
90	current->mm->arg_start = (unsigned long) p;
91	while (argc-->0) {
92		char c;
93		put_user(p,argv++);
94		do {
95			get_user(c,p++);
96		} while (c);
97	}
98	put_user(NULL,argv);
99	current->mm->arg_end = current->mm->env_start = (unsigned long) p;
100	while (envc-->0) {
101		char c;
102		put_user(p,envp++);
103		do {
104			get_user(c,p++);
105		} while (c);
106	}
107	put_user(NULL,envp);
108	current->mm->env_end = (unsigned long) p;
109	return sp;
110}
111
112/*
113 * These are the functions used to load a.out style executables and shared
114 * libraries.  There is no binary dependent code anywhere else.
115 */
116
117static int load_aout_binary(struct linux_binprm * bprm)
118{
119	struct pt_regs *regs = current_pt_regs();
120	struct exec ex;
121	unsigned long error;
122	unsigned long fd_offset;
123	unsigned long rlim;
124	int retval;
125
126	ex = *((struct exec *) bprm->buf);		/* exec-header */
127	if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != OMAGIC &&
128	     N_MAGIC(ex) != QMAGIC && N_MAGIC(ex) != NMAGIC) ||
129	    N_TRSIZE(ex) || N_DRSIZE(ex) ||
130	    i_size_read(file_inode(bprm->file)) < ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
131		return -ENOEXEC;
132	}
133
134	/*
135	 * Requires a mmap handler. This prevents people from using a.out
136	 * as part of an exploit attack against /proc-related vulnerabilities.
137	 */
138	if (!bprm->file->f_op->mmap)
139		return -ENOEXEC;
140
141	fd_offset = N_TXTOFF(ex);
142
143	/* Check initial limits. This avoids letting people circumvent
144	 * size limits imposed on them by creating programs with large
145	 * arrays in the data or bss.
146	 */
147	rlim = rlimit(RLIMIT_DATA);
148	if (rlim >= RLIM_INFINITY)
149		rlim = ~0;
150	if (ex.a_data + ex.a_bss > rlim)
151		return -ENOMEM;
152
153	/* Flush all traces of the currently running executable */
154	retval = begin_new_exec(bprm);
155	if (retval)
156		return retval;
157
158	/* OK, This is the point of no return */
159#ifdef __alpha__
160	SET_AOUT_PERSONALITY(bprm, ex);
161#else
162	set_personality(PER_LINUX);
163#endif
164	setup_new_exec(bprm);
165
166	current->mm->end_code = ex.a_text +
167		(current->mm->start_code = N_TXTADDR(ex));
168	current->mm->end_data = ex.a_data +
169		(current->mm->start_data = N_DATADDR(ex));
170	current->mm->brk = ex.a_bss +
171		(current->mm->start_brk = N_BSSADDR(ex));
172
173	retval = setup_arg_pages(bprm, STACK_TOP, EXSTACK_DEFAULT);
174	if (retval < 0)
175		return retval;
176
177
178	if (N_MAGIC(ex) == OMAGIC) {
179		unsigned long text_addr, map_size;
180		loff_t pos;
181
182		text_addr = N_TXTADDR(ex);
183
184#ifdef __alpha__
185		pos = fd_offset;
186		map_size = ex.a_text+ex.a_data + PAGE_SIZE - 1;
187#else
188		pos = 32;
189		map_size = ex.a_text+ex.a_data;
190#endif
191		error = vm_brk(text_addr & PAGE_MASK, map_size);
192		if (error)
193			return error;
194
195		error = read_code(bprm->file, text_addr, pos,
196				  ex.a_text+ex.a_data);
197		if ((signed long)error < 0)
198			return error;
199	} else {
200		if ((ex.a_text & 0xfff || ex.a_data & 0xfff) &&
201		    (N_MAGIC(ex) != NMAGIC) && printk_ratelimit())
202		{
203			printk(KERN_NOTICE "executable not page aligned\n");
204		}
205
206		if ((fd_offset & ~PAGE_MASK) != 0 && printk_ratelimit())
207		{
208			printk(KERN_WARNING
209			       "fd_offset is not page aligned. Please convert program: %pD\n",
210			       bprm->file);
211		}
212
213		if (!bprm->file->f_op->mmap||((fd_offset & ~PAGE_MASK) != 0)) {
214			error = vm_brk(N_TXTADDR(ex), ex.a_text+ex.a_data);
215			if (error)
216				return error;
217
218			read_code(bprm->file, N_TXTADDR(ex), fd_offset,
219				  ex.a_text + ex.a_data);
220			goto beyond_if;
221		}
222
223		error = vm_mmap(bprm->file, N_TXTADDR(ex), ex.a_text,
224			PROT_READ | PROT_EXEC, MAP_FIXED | MAP_PRIVATE,
225			fd_offset);
226
227		if (error != N_TXTADDR(ex))
228			return error;
229
230		error = vm_mmap(bprm->file, N_DATADDR(ex), ex.a_data,
231				PROT_READ | PROT_WRITE | PROT_EXEC,
232				MAP_FIXED | MAP_PRIVATE,
233				fd_offset + ex.a_text);
234		if (error != N_DATADDR(ex))
235			return error;
236	}
237beyond_if:
238	set_binfmt(&aout_format);
239
240	retval = set_brk(current->mm->start_brk, current->mm->brk);
241	if (retval < 0)
242		return retval;
243
244	current->mm->start_stack =
245		(unsigned long) create_aout_tables((char __user *) bprm->p, bprm);
246#ifdef __alpha__
247	regs->gp = ex.a_gpvalue;
248#endif
249	finalize_exec(bprm);
250	start_thread(regs, ex.a_entry, current->mm->start_stack);
251	return 0;
252}
253
254static int load_aout_library(struct file *file)
255{
256	struct inode * inode;
257	unsigned long bss, start_addr, len;
258	unsigned long error;
259	int retval;
260	struct exec ex;
261	loff_t pos = 0;
262
263	inode = file_inode(file);
264
265	retval = -ENOEXEC;
266	error = kernel_read(file, &ex, sizeof(ex), &pos);
267	if (error != sizeof(ex))
268		goto out;
269
270	/* We come in here for the regular a.out style of shared libraries */
271	if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != QMAGIC) || N_TRSIZE(ex) ||
272	    N_DRSIZE(ex) || ((ex.a_entry & 0xfff) && N_MAGIC(ex) == ZMAGIC) ||
273	    i_size_read(inode) < ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
274		goto out;
275	}
276
277	/*
278	 * Requires a mmap handler. This prevents people from using a.out
279	 * as part of an exploit attack against /proc-related vulnerabilities.
280	 */
281	if (!file->f_op->mmap)
282		goto out;
283
284	if (N_FLAGS(ex))
285		goto out;
286
287	/* For  QMAGIC, the starting address is 0x20 into the page.  We mask
288	   this off to get the starting address for the page */
289
290	start_addr =  ex.a_entry & 0xfffff000;
291
292	if ((N_TXTOFF(ex) & ~PAGE_MASK) != 0) {
293		if (printk_ratelimit())
294		{
295			printk(KERN_WARNING
296			       "N_TXTOFF is not page aligned. Please convert library: %pD\n",
297			       file);
298		}
299		retval = vm_brk(start_addr, ex.a_text + ex.a_data + ex.a_bss);
300		if (retval)
301			goto out;
302
303		read_code(file, start_addr, N_TXTOFF(ex),
304			  ex.a_text + ex.a_data);
305		retval = 0;
306		goto out;
307	}
308	/* Now use mmap to map the library into memory. */
309	error = vm_mmap(file, start_addr, ex.a_text + ex.a_data,
310			PROT_READ | PROT_WRITE | PROT_EXEC,
311			MAP_FIXED | MAP_PRIVATE;
312			N_TXTOFF(ex));
313	retval = error;
314	if (error != start_addr)
315		goto out;
316
317	len = PAGE_ALIGN(ex.a_text + ex.a_data);
318	bss = ex.a_text + ex.a_data + ex.a_bss;
319	if (bss > len) {
320		retval = vm_brk(start_addr + len, bss - len);
321		if (retval)
322			goto out;
323	}
324	retval = 0;
325out:
326	return retval;
327}
328
329static int __init init_aout_binfmt(void)
330{
331	register_binfmt(&aout_format);
332	return 0;
333}
334
335static void __exit exit_aout_binfmt(void)
336{
337	unregister_binfmt(&aout_format);
338}
339
340core_initcall(init_aout_binfmt);
341module_exit(exit_aout_binfmt);
342MODULE_LICENSE("GPL");
343