[PATCH 4.9 14/84] tipc: fix use-after-free

From: Greg Kroah-Hartman
Date: Mon Aug 28 2017 - 04:12:18 EST

4.9-stable review patch. If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@xxxxxxxxxx>


[ Upstream commit 5bfd37b4de5c98e86b12bd13be5aa46c7484a125 ]

syszkaller reported use-after-free in tipc [1]

When msg->rep skb is freed, set the pointer to NULL,
so that caller does not free it again.

[1]

==================================================================
BUG: KASAN: use-after-free in skb_push+0xd4/0xe0 net/core/skbuff.c:1466
Read of size 8 at addr ffff8801c6e71e90 by task syz-executor5/4115

CPU: 1 PID: 4115 Comm: syz-executor5 Not tainted 4.13.0-rc4+ #32
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:16 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:52
print_address_description+0x73/0x250 mm/kasan/report.c:252
kasan_report_error mm/kasan/report.c:351 [inline]
kasan_report+0x24e/0x340 mm/kasan/report.c:409
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
skb_push+0xd4/0xe0 net/core/skbuff.c:1466
tipc_nl_compat_recv+0x833/0x18f0 net/tipc/netlink_compat.c:1209
genl_family_rcv_msg+0x7b7/0xfb0 net/netlink/genetlink.c:598
genl_rcv_msg+0xb2/0x140 net/netlink/genetlink.c:623
netlink_rcv_skb+0x216/0x440 net/netlink/af_netlink.c:2397
genl_rcv+0x28/0x40 net/netlink/genetlink.c:634
netlink_unicast_kernel net/netlink/af_netlink.c:1265 [inline]
netlink_unicast+0x4e8/0x6f0 net/netlink/af_netlink.c:1291
netlink_sendmsg+0xa4a/0xe60 net/netlink/af_netlink.c:1854
sock_sendmsg_nosec net/socket.c:633 [inline]
sock_sendmsg+0xca/0x110 net/socket.c:643
sock_write_iter+0x31a/0x5d0 net/socket.c:898
call_write_iter include/linux/fs.h:1743 [inline]
new_sync_write fs/read_write.c:457 [inline]
__vfs_write+0x684/0x970 fs/read_write.c:470
vfs_write+0x189/0x510 fs/read_write.c:518
SYSC_write fs/read_write.c:565 [inline]
SyS_write+0xef/0x220 fs/read_write.c:557
entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x4512e9
RSP: 002b:00007f3bc8184c08 EFLAGS: 00000216 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000718000 RCX: 00000000004512e9
RDX: 0000000000000020 RSI: 0000000020fdb000 RDI: 0000000000000006
RBP: 0000000000000086 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000216 R12: 00000000004b5e76
R13: 00007f3bc8184b48 R14: 00000000004b5e86 R15: 0000000000000000

Allocated by task 4115:
save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
kmem_cache_alloc_node+0x13d/0x750 mm/slab.c:3651
__alloc_skb+0xf1/0x740 net/core/skbuff.c:219
alloc_skb include/linux/skbuff.h:903 [inline]
tipc_tlv_alloc+0x26/0xb0 net/tipc/netlink_compat.c:148
tipc_nl_compat_dumpit+0xf2/0x3c0 net/tipc/netlink_compat.c:248
tipc_nl_compat_handle net/tipc/netlink_compat.c:1130 [inline]
tipc_nl_compat_recv+0x756/0x18f0 net/tipc/netlink_compat.c:1199
genl_family_rcv_msg+0x7b7/0xfb0 net/netlink/genetlink.c:598
genl_rcv_msg+0xb2/0x140 net/netlink/genetlink.c:623
netlink_rcv_skb+0x216/0x440 net/netlink/af_netlink.c:2397
genl_rcv+0x28/0x40 net/netlink/genetlink.c:634
netlink_unicast_kernel net/netlink/af_netlink.c:1265 [inline]
netlink_unicast+0x4e8/0x6f0 net/netlink/af_netlink.c:1291
netlink_sendmsg+0xa4a/0xe60 net/netlink/af_netlink.c:1854
sock_sendmsg_nosec net/socket.c:633 [inline]
sock_sendmsg+0xca/0x110 net/socket.c:643
sock_write_iter+0x31a/0x5d0 net/socket.c:898
call_write_iter include/linux/fs.h:1743 [inline]
new_sync_write fs/read_write.c:457 [inline]
__vfs_write+0x684/0x970 fs/read_write.c:470
vfs_write+0x189/0x510 fs/read_write.c:518
SYSC_write fs/read_write.c:565 [inline]
SyS_write+0xef/0x220 fs/read_write.c:557
entry_SYSCALL_64_fastpath+0x1f/0xbe

Freed by task 4115:
save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
__cache_free mm/slab.c:3503 [inline]
kmem_cache_free+0x77/0x280 mm/slab.c:3763
kfree_skbmem+0x1a1/0x1d0 net/core/skbuff.c:622
__kfree_skb net/core/skbuff.c:682 [inline]
kfree_skb+0x165/0x4c0 net/core/skbuff.c:699
tipc_nl_compat_dumpit+0x36a/0x3c0 net/tipc/netlink_compat.c:260
tipc_nl_compat_handle net/tipc/netlink_compat.c:1130 [inline]
tipc_nl_compat_recv+0x756/0x18f0 net/tipc/netlink_compat.c:1199
genl_family_rcv_msg+0x7b7/0xfb0 net/netlink/genetlink.c:598
genl_rcv_msg+0xb2/0x140 net/netlink/genetlink.c:623
netlink_rcv_skb+0x216/0x440 net/netlink/af_netlink.c:2397
genl_rcv+0x28/0x40 net/netlink/genetlink.c:634
netlink_unicast_kernel net/netlink/af_netlink.c:1265 [inline]
netlink_unicast+0x4e8/0x6f0 net/netlink/af_netlink.c:1291
netlink_sendmsg+0xa4a/0xe60 net/netlink/af_netlink.c:1854
sock_sendmsg_nosec net/socket.c:633 [inline]
sock_sendmsg+0xca/0x110 net/socket.c:643
sock_write_iter+0x31a/0x5d0 net/socket.c:898
call_write_iter include/linux/fs.h:1743 [inline]
new_sync_write fs/read_write.c:457 [inline]
__vfs_write+0x684/0x970 fs/read_write.c:470
vfs_write+0x189/0x510 fs/read_write.c:518
SYSC_write fs/read_write.c:565 [inline]
SyS_write+0xef/0x220 fs/read_write.c:557
entry_SYSCALL_64_fastpath+0x1f/0xbe

The buggy address belongs to the object at ffff8801c6e71dc0
which belongs to the cache skbuff_head_cache of size 224
The buggy address is located 208 bytes inside of
224-byte region [ffff8801c6e71dc0, ffff8801c6e71ea0)
The buggy address belongs to the page:
page:ffffea00071b9c40 count:1 mapcount:0 mapping:ffff8801c6e71000 index:0x0
flags: 0x200000000000100(slab)
raw: 0200000000000100 ffff8801c6e71000 0000000000000000 000000010000000c
raw: ffffea0007224a20 ffff8801d98caf48 ffff8801d9e79040 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801c6e71d80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
ffff8801c6e71e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801c6e71e80: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc
^
ffff8801c6e71f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8801c6e71f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Jon Maloy <jon.maloy@xxxxxxxxxxxx>
Cc: Ying Xue <ying.xue@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/tipc/netlink_compat.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

--- a/net/tipc/netlink_compat.c
+++ b/net/tipc/netlink_compat.c
@@ -258,13 +258,15 @@ static int tipc_nl_compat_dumpit(struct
arg = nlmsg_new(0, GFP_KERNEL);
if (!arg) {
kfree_skb(msg->rep);
+ msg->rep = NULL;
return -ENOMEM;
}

err = __tipc_nl_compat_dumpit(cmd, msg, arg);
- if (err)
+ if (err) {
kfree_skb(msg->rep);
-
+ msg->rep = NULL;
+ }
kfree_skb(arg);

return err;