linux/net/ax25/ax25_route.c
Eric Dumazet 63530aba78 ax25: fix possible use-after-free
syzbot found that ax25 routes where not properly protected
against concurrent use [1].

In this particular report the bug happened while
copying ax25->digipeat.

Fix this problem by making sure we call ax25_get_route()
while ax25_route_lock is held, so that no modification
could happen while using the route.

The current two ax25_get_route() callers do not sleep,
so this change should be fine.

Once we do that, ax25_get_route() no longer needs to
grab a reference on the found route.

[1]
ax25_connect(): syz-executor0 uses autobind, please contact jreuter@yaina.de
BUG: KASAN: use-after-free in memcpy include/linux/string.h:352 [inline]
BUG: KASAN: use-after-free in kmemdup+0x42/0x60 mm/util.c:113
Read of size 66 at addr ffff888066641a80 by task syz-executor2/531

ax25_connect(): syz-executor0 uses autobind, please contact jreuter@yaina.de
CPU: 1 PID: 531 Comm: syz-executor2 Not tainted 5.0.0-rc2+ #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1db/0x2d0 lib/dump_stack.c:113
 print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187
 kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
 check_memory_region_inline mm/kasan/generic.c:185 [inline]
 check_memory_region+0x123/0x190 mm/kasan/generic.c:191
 memcpy+0x24/0x50 mm/kasan/common.c:130
 memcpy include/linux/string.h:352 [inline]
 kmemdup+0x42/0x60 mm/util.c:113
 kmemdup include/linux/string.h:425 [inline]
 ax25_rt_autobind+0x25d/0x750 net/ax25/ax25_route.c:424
 ax25_connect.cold+0x30/0xa4 net/ax25/af_ax25.c:1224
 __sys_connect+0x357/0x490 net/socket.c:1664
 __do_sys_connect net/socket.c:1675 [inline]
 __se_sys_connect net/socket.c:1672 [inline]
 __x64_sys_connect+0x73/0xb0 net/socket.c:1672
 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x458099
Code: 6d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 3b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f870ee22c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000458099
RDX: 0000000000000048 RSI: 0000000020000080 RDI: 0000000000000005
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
ax25_connect(): syz-executor4 uses autobind, please contact jreuter@yaina.de
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f870ee236d4
R13: 00000000004be48e R14: 00000000004ce9a8 R15: 00000000ffffffff

Allocated by task 526:
 save_stack+0x45/0xd0 mm/kasan/common.c:73
 set_track mm/kasan/common.c:85 [inline]
 __kasan_kmalloc mm/kasan/common.c:496 [inline]
 __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:469
 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:504
ax25_connect(): syz-executor5 uses autobind, please contact jreuter@yaina.de
 kmem_cache_alloc_trace+0x151/0x760 mm/slab.c:3609
 kmalloc include/linux/slab.h:545 [inline]
 ax25_rt_add net/ax25/ax25_route.c:95 [inline]
 ax25_rt_ioctl+0x3b9/0x1270 net/ax25/ax25_route.c:233
 ax25_ioctl+0x322/0x10b0 net/ax25/af_ax25.c:1763
 sock_do_ioctl+0xe2/0x400 net/socket.c:950
 sock_ioctl+0x32f/0x6c0 net/socket.c:1074
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0x107b/0x17d0 fs/ioctl.c:696
 ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

ax25_connect(): syz-executor5 uses autobind, please contact jreuter@yaina.de
Freed by task 550:
 save_stack+0x45/0xd0 mm/kasan/common.c:73
 set_track mm/kasan/common.c:85 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:458
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:466
 __cache_free mm/slab.c:3487 [inline]
 kfree+0xcf/0x230 mm/slab.c:3806
 ax25_rt_add net/ax25/ax25_route.c:92 [inline]
 ax25_rt_ioctl+0x304/0x1270 net/ax25/ax25_route.c:233
 ax25_ioctl+0x322/0x10b0 net/ax25/af_ax25.c:1763
 sock_do_ioctl+0xe2/0x400 net/socket.c:950
 sock_ioctl+0x32f/0x6c0 net/socket.c:1074
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0x107b/0x17d0 fs/ioctl.c:696
 ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff888066641a80
 which belongs to the cache kmalloc-96 of size 96
The buggy address is located 0 bytes inside of
 96-byte region [ffff888066641a80, ffff888066641ae0)
The buggy address belongs to the page:
page:ffffea0001999040 count:1 mapcount:0 mapping:ffff88812c3f04c0 index:0x0
flags: 0x1fffc0000000200(slab)
ax25_connect(): syz-executor4 uses autobind, please contact jreuter@yaina.de
raw: 01fffc0000000200 ffffea0001817948 ffffea0002341dc8 ffff88812c3f04c0
raw: 0000000000000000 ffff888066641000 0000000100000020 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888066641980: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff888066641a00: 00 00 00 00 00 00 00 00 02 fc fc fc fc fc fc fc
>ffff888066641a80: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
                   ^
 ffff888066641b00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff888066641b80: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2019-01-23 11:18:00 -08:00

489 lines
11 KiB
C

/*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* Copyright (C) Alan Cox GW4PTS (alan@lxorguk.ukuu.org.uk)
* Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
* Copyright (C) Steven Whitehouse GW7RRM (stevew@acm.org)
* Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
* Copyright (C) Hans-Joachim Hetscher DD8NE (dd8ne@bnv-bamberg.de)
* Copyright (C) Frederic Rible F1OAT (frible@teaser.fr)
*/
#include <linux/capability.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/timer.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/slab.h>
#include <net/ax25.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/skbuff.h>
#include <linux/spinlock.h>
#include <net/sock.h>
#include <linux/uaccess.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/seq_file.h>
#include <linux/export.h>
static ax25_route *ax25_route_list;
DEFINE_RWLOCK(ax25_route_lock);
void ax25_rt_device_down(struct net_device *dev)
{
ax25_route *s, *t, *ax25_rt;
write_lock_bh(&ax25_route_lock);
ax25_rt = ax25_route_list;
while (ax25_rt != NULL) {
s = ax25_rt;
ax25_rt = ax25_rt->next;
if (s->dev == dev) {
if (ax25_route_list == s) {
ax25_route_list = s->next;
kfree(s->digipeat);
kfree(s);
} else {
for (t = ax25_route_list; t != NULL; t = t->next) {
if (t->next == s) {
t->next = s->next;
kfree(s->digipeat);
kfree(s);
break;
}
}
}
}
}
write_unlock_bh(&ax25_route_lock);
}
static int __must_check ax25_rt_add(struct ax25_routes_struct *route)
{
ax25_route *ax25_rt;
ax25_dev *ax25_dev;
int i;
if ((ax25_dev = ax25_addr_ax25dev(&route->port_addr)) == NULL)
return -EINVAL;
if (route->digi_count > AX25_MAX_DIGIS)
return -EINVAL;
write_lock_bh(&ax25_route_lock);
ax25_rt = ax25_route_list;
while (ax25_rt != NULL) {
if (ax25cmp(&ax25_rt->callsign, &route->dest_addr) == 0 &&
ax25_rt->dev == ax25_dev->dev) {
kfree(ax25_rt->digipeat);
ax25_rt->digipeat = NULL;
if (route->digi_count != 0) {
if ((ax25_rt->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) {
write_unlock_bh(&ax25_route_lock);
return -ENOMEM;
}
ax25_rt->digipeat->lastrepeat = -1;
ax25_rt->digipeat->ndigi = route->digi_count;
for (i = 0; i < route->digi_count; i++) {
ax25_rt->digipeat->repeated[i] = 0;
ax25_rt->digipeat->calls[i] = route->digi_addr[i];
}
}
write_unlock_bh(&ax25_route_lock);
return 0;
}
ax25_rt = ax25_rt->next;
}
if ((ax25_rt = kmalloc(sizeof(ax25_route), GFP_ATOMIC)) == NULL) {
write_unlock_bh(&ax25_route_lock);
return -ENOMEM;
}
refcount_set(&ax25_rt->refcount, 1);
ax25_rt->callsign = route->dest_addr;
ax25_rt->dev = ax25_dev->dev;
ax25_rt->digipeat = NULL;
ax25_rt->ip_mode = ' ';
if (route->digi_count != 0) {
if ((ax25_rt->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) {
write_unlock_bh(&ax25_route_lock);
kfree(ax25_rt);
return -ENOMEM;
}
ax25_rt->digipeat->lastrepeat = -1;
ax25_rt->digipeat->ndigi = route->digi_count;
for (i = 0; i < route->digi_count; i++) {
ax25_rt->digipeat->repeated[i] = 0;
ax25_rt->digipeat->calls[i] = route->digi_addr[i];
}
}
ax25_rt->next = ax25_route_list;
ax25_route_list = ax25_rt;
write_unlock_bh(&ax25_route_lock);
return 0;
}
void __ax25_put_route(ax25_route *ax25_rt)
{
kfree(ax25_rt->digipeat);
kfree(ax25_rt);
}
static int ax25_rt_del(struct ax25_routes_struct *route)
{
ax25_route *s, *t, *ax25_rt;
ax25_dev *ax25_dev;
if ((ax25_dev = ax25_addr_ax25dev(&route->port_addr)) == NULL)
return -EINVAL;
write_lock_bh(&ax25_route_lock);
ax25_rt = ax25_route_list;
while (ax25_rt != NULL) {
s = ax25_rt;
ax25_rt = ax25_rt->next;
if (s->dev == ax25_dev->dev &&
ax25cmp(&route->dest_addr, &s->callsign) == 0) {
if (ax25_route_list == s) {
ax25_route_list = s->next;
ax25_put_route(s);
} else {
for (t = ax25_route_list; t != NULL; t = t->next) {
if (t->next == s) {
t->next = s->next;
ax25_put_route(s);
break;
}
}
}
}
}
write_unlock_bh(&ax25_route_lock);
return 0;
}
static int ax25_rt_opt(struct ax25_route_opt_struct *rt_option)
{
ax25_route *ax25_rt;
ax25_dev *ax25_dev;
int err = 0;
if ((ax25_dev = ax25_addr_ax25dev(&rt_option->port_addr)) == NULL)
return -EINVAL;
write_lock_bh(&ax25_route_lock);
ax25_rt = ax25_route_list;
while (ax25_rt != NULL) {
if (ax25_rt->dev == ax25_dev->dev &&
ax25cmp(&rt_option->dest_addr, &ax25_rt->callsign) == 0) {
switch (rt_option->cmd) {
case AX25_SET_RT_IPMODE:
switch (rt_option->arg) {
case ' ':
case 'D':
case 'V':
ax25_rt->ip_mode = rt_option->arg;
break;
default:
err = -EINVAL;
goto out;
}
break;
default:
err = -EINVAL;
goto out;
}
}
ax25_rt = ax25_rt->next;
}
out:
write_unlock_bh(&ax25_route_lock);
return err;
}
int ax25_rt_ioctl(unsigned int cmd, void __user *arg)
{
struct ax25_route_opt_struct rt_option;
struct ax25_routes_struct route;
switch (cmd) {
case SIOCADDRT:
if (copy_from_user(&route, arg, sizeof(route)))
return -EFAULT;
return ax25_rt_add(&route);
case SIOCDELRT:
if (copy_from_user(&route, arg, sizeof(route)))
return -EFAULT;
return ax25_rt_del(&route);
case SIOCAX25OPTRT:
if (copy_from_user(&rt_option, arg, sizeof(rt_option)))
return -EFAULT;
return ax25_rt_opt(&rt_option);
default:
return -EINVAL;
}
}
#ifdef CONFIG_PROC_FS
static void *ax25_rt_seq_start(struct seq_file *seq, loff_t *pos)
__acquires(ax25_route_lock)
{
struct ax25_route *ax25_rt;
int i = 1;
read_lock(&ax25_route_lock);
if (*pos == 0)
return SEQ_START_TOKEN;
for (ax25_rt = ax25_route_list; ax25_rt != NULL; ax25_rt = ax25_rt->next) {
if (i == *pos)
return ax25_rt;
++i;
}
return NULL;
}
static void *ax25_rt_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
++*pos;
return (v == SEQ_START_TOKEN) ? ax25_route_list :
((struct ax25_route *) v)->next;
}
static void ax25_rt_seq_stop(struct seq_file *seq, void *v)
__releases(ax25_route_lock)
{
read_unlock(&ax25_route_lock);
}
static int ax25_rt_seq_show(struct seq_file *seq, void *v)
{
char buf[11];
if (v == SEQ_START_TOKEN)
seq_puts(seq, "callsign dev mode digipeaters\n");
else {
struct ax25_route *ax25_rt = v;
const char *callsign;
int i;
if (ax25cmp(&ax25_rt->callsign, &null_ax25_address) == 0)
callsign = "default";
else
callsign = ax2asc(buf, &ax25_rt->callsign);
seq_printf(seq, "%-9s %-4s",
callsign,
ax25_rt->dev ? ax25_rt->dev->name : "???");
switch (ax25_rt->ip_mode) {
case 'V':
seq_puts(seq, " vc");
break;
case 'D':
seq_puts(seq, " dg");
break;
default:
seq_puts(seq, " *");
break;
}
if (ax25_rt->digipeat != NULL)
for (i = 0; i < ax25_rt->digipeat->ndigi; i++)
seq_printf(seq, " %s",
ax2asc(buf, &ax25_rt->digipeat->calls[i]));
seq_puts(seq, "\n");
}
return 0;
}
const struct seq_operations ax25_rt_seqops = {
.start = ax25_rt_seq_start,
.next = ax25_rt_seq_next,
.stop = ax25_rt_seq_stop,
.show = ax25_rt_seq_show,
};
#endif
/*
* Find AX.25 route
*
* Only routes with a reference count of zero can be destroyed.
* Must be called with ax25_route_lock read locked.
*/
ax25_route *ax25_get_route(ax25_address *addr, struct net_device *dev)
{
ax25_route *ax25_spe_rt = NULL;
ax25_route *ax25_def_rt = NULL;
ax25_route *ax25_rt;
/*
* Bind to the physical interface we heard them on, or the default
* route if none is found;
*/
for (ax25_rt = ax25_route_list; ax25_rt != NULL; ax25_rt = ax25_rt->next) {
if (dev == NULL) {
if (ax25cmp(&ax25_rt->callsign, addr) == 0 && ax25_rt->dev != NULL)
ax25_spe_rt = ax25_rt;
if (ax25cmp(&ax25_rt->callsign, &null_ax25_address) == 0 && ax25_rt->dev != NULL)
ax25_def_rt = ax25_rt;
} else {
if (ax25cmp(&ax25_rt->callsign, addr) == 0 && ax25_rt->dev == dev)
ax25_spe_rt = ax25_rt;
if (ax25cmp(&ax25_rt->callsign, &null_ax25_address) == 0 && ax25_rt->dev == dev)
ax25_def_rt = ax25_rt;
}
}
ax25_rt = ax25_def_rt;
if (ax25_spe_rt != NULL)
ax25_rt = ax25_spe_rt;
return ax25_rt;
}
/*
* Adjust path: If you specify a default route and want to connect
* a target on the digipeater path but w/o having a special route
* set before, the path has to be truncated from your target on.
*/
static inline void ax25_adjust_path(ax25_address *addr, ax25_digi *digipeat)
{
int k;
for (k = 0; k < digipeat->ndigi; k++) {
if (ax25cmp(addr, &digipeat->calls[k]) == 0)
break;
}
digipeat->ndigi = k;
}
/*
* Find which interface to use.
*/
int ax25_rt_autobind(ax25_cb *ax25, ax25_address *addr)
{
ax25_uid_assoc *user;
ax25_route *ax25_rt;
int err = 0;
ax25_route_lock_use();
ax25_rt = ax25_get_route(addr, NULL);
if (!ax25_rt) {
ax25_route_lock_unuse();
return -EHOSTUNREACH;
}
if ((ax25->ax25_dev = ax25_dev_ax25dev(ax25_rt->dev)) == NULL) {
err = -EHOSTUNREACH;
goto put;
}
user = ax25_findbyuid(current_euid());
if (user) {
ax25->source_addr = user->call;
ax25_uid_put(user);
} else {
if (ax25_uid_policy && !capable(CAP_NET_BIND_SERVICE)) {
err = -EPERM;
goto put;
}
ax25->source_addr = *(ax25_address *)ax25->ax25_dev->dev->dev_addr;
}
if (ax25_rt->digipeat != NULL) {
ax25->digipeat = kmemdup(ax25_rt->digipeat, sizeof(ax25_digi),
GFP_ATOMIC);
if (ax25->digipeat == NULL) {
err = -ENOMEM;
goto put;
}
ax25_adjust_path(addr, ax25->digipeat);
}
if (ax25->sk != NULL) {
bh_lock_sock(ax25->sk);
sock_reset_flag(ax25->sk, SOCK_ZAPPED);
bh_unlock_sock(ax25->sk);
}
put:
ax25_route_lock_unuse();
return err;
}
struct sk_buff *ax25_rt_build_path(struct sk_buff *skb, ax25_address *src,
ax25_address *dest, ax25_digi *digi)
{
struct sk_buff *skbn;
unsigned char *bp;
int len;
len = digi->ndigi * AX25_ADDR_LEN;
if (skb_headroom(skb) < len) {
if ((skbn = skb_realloc_headroom(skb, len)) == NULL) {
printk(KERN_CRIT "AX.25: ax25_dg_build_path - out of memory\n");
return NULL;
}
if (skb->sk != NULL)
skb_set_owner_w(skbn, skb->sk);
consume_skb(skb);
skb = skbn;
}
bp = skb_push(skb, len);
ax25_addr_build(bp, src, dest, digi, AX25_COMMAND, AX25_MODULUS);
return skb;
}
/*
* Free all memory associated with routing structures.
*/
void __exit ax25_rt_free(void)
{
ax25_route *s, *ax25_rt = ax25_route_list;
write_lock_bh(&ax25_route_lock);
while (ax25_rt != NULL) {
s = ax25_rt;
ax25_rt = ax25_rt->next;
kfree(s->digipeat);
kfree(s);
}
write_unlock_bh(&ax25_route_lock);
}