linux/net/ax25/ax25_ip.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

252 lines
5.5 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) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
*/
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/timer.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 <net/sock.h>
#include <linux/uaccess.h>
#include <linux/fcntl.h>
#include <linux/termios.h> /* For TIOCINQ/OUTQ */
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/notifier.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
#include <linux/sysctl.h>
#include <net/ip.h>
#include <net/arp.h>
/*
* IP over AX.25 encapsulation.
*/
/*
* Shove an AX.25 UI header on an IP packet and handle ARP
*/
#ifdef CONFIG_INET
static int ax25_hard_header(struct sk_buff *skb, struct net_device *dev,
unsigned short type, const void *daddr,
const void *saddr, unsigned int len)
{
unsigned char *buff;
/* they sometimes come back to us... */
if (type == ETH_P_AX25)
return 0;
/* header is an AX.25 UI frame from us to them */
buff = skb_push(skb, AX25_HEADER_LEN);
*buff++ = 0x00; /* KISS DATA */
if (daddr != NULL)
memcpy(buff, daddr, dev->addr_len); /* Address specified */
buff[6] &= ~AX25_CBIT;
buff[6] &= ~AX25_EBIT;
buff[6] |= AX25_SSSID_SPARE;
buff += AX25_ADDR_LEN;
if (saddr != NULL)
memcpy(buff, saddr, dev->addr_len);
else
memcpy(buff, dev->dev_addr, dev->addr_len);
buff[6] &= ~AX25_CBIT;
buff[6] |= AX25_EBIT;
buff[6] |= AX25_SSSID_SPARE;
buff += AX25_ADDR_LEN;
*buff++ = AX25_UI; /* UI */
/* Append a suitable AX.25 PID */
switch (type) {
case ETH_P_IP:
*buff++ = AX25_P_IP;
break;
case ETH_P_ARP:
*buff++ = AX25_P_ARP;
break;
default:
printk(KERN_ERR "AX.25: ax25_hard_header - wrong protocol type 0x%2.2x\n", type);
*buff++ = 0;
break;
}
if (daddr != NULL)
return AX25_HEADER_LEN;
return -AX25_HEADER_LEN; /* Unfinished header */
}
netdev_tx_t ax25_ip_xmit(struct sk_buff *skb)
{
struct sk_buff *ourskb;
unsigned char *bp = skb->data;
ax25_route *route;
struct net_device *dev = NULL;
ax25_address *src, *dst;
ax25_digi *digipeat = NULL;
ax25_dev *ax25_dev;
ax25_cb *ax25;
char ip_mode = ' ';
dst = (ax25_address *)(bp + 1);
src = (ax25_address *)(bp + 8);
ax25_route_lock_use();
route = ax25_get_route(dst, NULL);
if (route) {
digipeat = route->digipeat;
dev = route->dev;
ip_mode = route->ip_mode;
}
if (dev == NULL)
dev = skb->dev;
if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL) {
kfree_skb(skb);
goto put;
}
if (bp[16] == AX25_P_IP) {
if (ip_mode == 'V' || (ip_mode == ' ' && ax25_dev->values[AX25_VALUES_IPDEFMODE])) {
/*
* We copy the buffer and release the original thereby
* keeping it straight
*
* Note: we report 1 back so the caller will
* not feed the frame direct to the physical device
* We don't want that to happen. (It won't be upset
* as we have pulled the frame from the queue by
* freeing it).
*
* NB: TCP modifies buffers that are still
* on a device queue, thus we use skb_copy()
* instead of using skb_clone() unless this
* gets fixed.
*/
ax25_address src_c;
ax25_address dst_c;
if ((ourskb = skb_copy(skb, GFP_ATOMIC)) == NULL) {
kfree_skb(skb);
goto put;
}
if (skb->sk != NULL)
skb_set_owner_w(ourskb, skb->sk);
kfree_skb(skb);
/* dl9sau: bugfix
* after kfree_skb(), dst and src which were pointer
* to bp which is part of skb->data would not be valid
* anymore hope that after skb_pull(ourskb, ..) our
* dsc_c and src_c will not become invalid
*/
bp = ourskb->data;
dst_c = *(ax25_address *)(bp + 1);
src_c = *(ax25_address *)(bp + 8);
skb_pull(ourskb, AX25_HEADER_LEN - 1); /* Keep PID */
skb_reset_network_header(ourskb);
ax25=ax25_send_frame(
ourskb,
ax25_dev->values[AX25_VALUES_PACLEN],
&src_c,
&dst_c, digipeat, dev);
if (ax25) {
ax25_cb_put(ax25);
}
goto put;
}
}
bp[7] &= ~AX25_CBIT;
bp[7] &= ~AX25_EBIT;
bp[7] |= AX25_SSSID_SPARE;
bp[14] &= ~AX25_CBIT;
bp[14] |= AX25_EBIT;
bp[14] |= AX25_SSSID_SPARE;
skb_pull(skb, AX25_KISS_HEADER_LEN);
if (digipeat != NULL) {
if ((ourskb = ax25_rt_build_path(skb, src, dst, route->digipeat)) == NULL) {
kfree_skb(skb);
goto put;
}
skb = ourskb;
}
ax25_queue_xmit(skb, dev);
put:
ax25_route_lock_unuse();
return NETDEV_TX_OK;
}
#else /* INET */
static int ax25_hard_header(struct sk_buff *skb, struct net_device *dev,
unsigned short type, const void *daddr,
const void *saddr, unsigned int len)
{
return -AX25_HEADER_LEN;
}
netdev_tx_t ax25_ip_xmit(struct sk_buff *skb)
{
kfree_skb(skb);
return NETDEV_TX_OK;
}
#endif
static bool ax25_validate_header(const char *header, unsigned int len)
{
ax25_digi digi;
if (!len)
return false;
if (header[0])
return true;
return ax25_addr_parse(header + 1, len - 1, NULL, NULL, &digi, NULL,
NULL);
}
const struct header_ops ax25_header_ops = {
.create = ax25_hard_header,
.validate = ax25_validate_header,
};
EXPORT_SYMBOL(ax25_header_ops);
EXPORT_SYMBOL(ax25_ip_xmit);