KASAN: use-after-free Read in tcp_ack

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: f02af7b0 Merge 4.14.143 into android-4.14
git tree: android-4.14
console output: https://syzkaller.appspot.com/x/log.txt?x=100821b9600000
kernel config: https://syzkaller.appspot.com/x/.config?x=4d9cf2fd50fd7015
dashboard link: https://syzkaller.appspot.com/bug?extid=e23f6a682a69d1555eae
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+e23f6a...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in tcp_ack_probe net/ipv4/tcp_input.c:3293
[inline]
BUG: KASAN: use-after-free in tcp_ack+0x3beb/0x42c0
net/ipv4/tcp_input.c:3715
Read of size 4 at addr ffff8881c11062ac by task syz-executor.0/7997

CPU: 0 PID: 7997 Comm: syz-executor.0 Not tainted 4.14.143+ #0
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0xca/0x134 lib/dump_stack.c:53
print_address_description+0x60/0x226 mm/kasan/report.c:187
__kasan_report.cold+0x1a/0x41 mm/kasan/report.c:316
tcp_ack_probe net/ipv4/tcp_input.c:3293 [inline]
tcp_ack+0x3beb/0x42c0 net/ipv4/tcp_input.c:3715
tcp_rcv_established+0x4a9/0x1610 net/ipv4/tcp_input.c:5556
tcp_v6_do_rcv+0xcbd/0x10d0 net/ipv6/tcp_ipv6.c:1301
tcp_v6_rcv+0x20db/0x2ec0 net/ipv6/tcp_ipv6.c:1519
ip6_input_finish+0x3d6/0x1500 net/ipv6/ip6_input.c:284
NF_HOOK include/linux/netfilter.h:250 [inline]
ip6_input+0x1fd/0x320 net/ipv6/ip6_input.c:327
dst_input include/net/dst.h:468 [inline]
ip6_rcv_finish+0x148/0x640 net/ipv6/ip6_input.c:71
NF_HOOK include/linux/netfilter.h:250 [inline]
ipv6_rcv+0xcf6/0x1bb0 net/ipv6/ip6_input.c:208
__netif_receive_skb_core+0x13ad/0x2cf0 net/core/dev.c:4477
__netif_receive_skb+0x66/0x210 net/core/dev.c:4515
process_backlog+0x1dc/0x640 net/core/dev.c:5197
napi_poll net/core/dev.c:5598 [inline]
net_rx_action+0x366/0xcd0 net/core/dev.c:5664
__do_softirq+0x234/0x9ec kernel/softirq.c:288
do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1015
</IRQ>
do_softirq.part.0+0x5b/0x60 kernel/softirq.c:332
do_softirq kernel/softirq.c:324 [inline]
__local_bh_enable_ip+0xb0/0xc0 kernel/softirq.c:185
local_bh_enable include/linux/bottom_half.h:32 [inline]
rcu_read_unlock_bh include/linux/rcupdate.h:725 [inline]
ip6_finish_output2+0x106e/0x1fa0 net/ipv6/ip6_output.c:121
ip6_finish_output+0x64b/0xb40 net/ipv6/ip6_output.c:154
NF_HOOK_COND include/linux/netfilter.h:239 [inline]
ip6_output+0x1dc/0x680 net/ipv6/ip6_output.c:171
dst_output include/net/dst.h:462 [inline]
NF_HOOK include/linux/netfilter.h:250 [inline]
ip6_xmit+0x10a1/0x1ca0 net/ipv6/ip6_output.c:275
inet6_csk_xmit+0x298/0x500 net/ipv6/inet6_connection_sock.c:139
__tcp_transmit_skb+0x18bc/0x2e20 net/ipv4/tcp_output.c:1130
tcp_transmit_skb net/ipv4/tcp_output.c:1146 [inline]
tcp_write_xmit+0x510/0x4730 net/ipv4/tcp_output.c:2382
__tcp_push_pending_frames+0xa0/0x230 net/ipv4/tcp_output.c:2563
tcp_send_fin+0x154/0xbc0 net/ipv4/tcp_output.c:3115
tcp_close+0xc62/0xf40 net/ipv4/tcp.c:2221
inet_release+0xe9/0x1c0 net/ipv4/af_inet.c:423
inet6_release+0x4c/0x70 net/ipv6/af_inet6.c:449
__sock_release+0xd2/0x2c0 net/socket.c:602
sock_close+0x15/0x20 net/socket.c:1139
__fput+0x25e/0x710 fs/file_table.c:210
task_work_run+0x125/0x1a0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x13b/0x160 arch/x86/entry/common.c:164
prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
do_syscall_64+0x3a3/0x520 arch/x86/entry/common.c:297
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x4598e9
RSP: 002b:00007f3cb5413c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000120
RAX: fffffffffffffff2 RBX: 0000000000000004 RCX: 00000000004598e9
RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000007
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f3cb54146d4
R13: 00000000004bf7fc R14: 00000000004d1290 R15: 00000000ffffffff

Allocated by task 8008:
save_stack mm/kasan/common.c:76 [inline]
set_track mm/kasan/common.c:85 [inline]
__kasan_kmalloc.part.0+0x53/0xc0 mm/kasan/common.c:495
slab_post_alloc_hook mm/slab.h:439 [inline]
slab_alloc_node mm/slub.c:2792 [inline]
slab_alloc mm/slub.c:2800 [inline]
kmem_cache_alloc+0xee/0x360 mm/slub.c:2805
kmem_cache_alloc_node include/linux/slab.h:361 [inline]
__alloc_skb+0xea/0x5c0 net/core/skbuff.c:193
alloc_skb_fclone include/linux/skbuff.h:1022 [inline]
sk_stream_alloc_skb+0xf4/0x8a0 net/ipv4/tcp.c:855
tcp_sendmsg_locked+0xf11/0x2f50 net/ipv4/tcp.c:1301
tcp_sendmsg+0x2b/0x40 net/ipv4/tcp.c:1457
inet_sendmsg+0x15b/0x520 net/ipv4/af_inet.c:760
sock_sendmsg_nosec net/socket.c:646 [inline]
sock_sendmsg+0xb7/0x100 net/socket.c:656
SYSC_sendto net/socket.c:1763 [inline]
SyS_sendto+0x1de/0x2f0 net/socket.c:1731
do_syscall_64+0x19b/0x520 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
0xffffffffffffffff

Freed by task 8008:
save_stack mm/kasan/common.c:76 [inline]
set_track mm/kasan/common.c:85 [inline]
__kasan_slab_free+0x164/0x210 mm/kasan/common.c:457
slab_free_hook mm/slub.c:1407 [inline]
slab_free_freelist_hook mm/slub.c:1458 [inline]
slab_free mm/slub.c:3039 [inline]
kmem_cache_free+0xd7/0x3b0 mm/slub.c:3055
kfree_skbmem+0x84/0x110 net/core/skbuff.c:607
sk_wmem_free_skb include/net/sock.h:1416 [inline]
tcp_remove_empty_skb net/ipv4/tcp.c:929 [inline]
tcp_remove_empty_skb+0x264/0x320 net/ipv4/tcp.c:923
tcp_sendmsg_locked+0x1c09/0x2f50 net/ipv4/tcp.c:1435
tcp_sendmsg+0x2b/0x40 net/ipv4/tcp.c:1457
inet_sendmsg+0x15b/0x520 net/ipv4/af_inet.c:760
sock_sendmsg_nosec net/socket.c:646 [inline]
sock_sendmsg+0xb7/0x100 net/socket.c:656
SYSC_sendto net/socket.c:1763 [inline]
SyS_sendto+0x1de/0x2f0 net/socket.c:1731
do_syscall_64+0x19b/0x520 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
0xffffffffffffffff

The buggy address belongs to the object at ffff8881c1106280
which belongs to the cache skbuff_fclone_cache of size 456
The buggy address is located 44 bytes inside of
456-byte region [ffff8881c1106280, ffff8881c1106448)
The buggy address belongs to the page:
page:ffffea0007044180 count:1 mapcount:0 mapping: (null) index:0x0
compound_mapcount: 0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 0000000000000000 0000000000000000 00000001000c000c
raw: ffffea0006c75380 0000000a0000000a ffff8881d6770400 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8881c1106180: fb fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc
ffff8881c1106200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff8881c1106280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8881c1106300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8881c1106380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.