KASAN: use-after-free Read in sctp_epaddr_lookup_transport

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: a97b95653383 drivers/net/ethernet/qlogic/qed/qed_rdma.h: f..
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=1217d26d400000
kernel config: https://syzkaller.appspot.com/x/.config?x=d86f24333880b605
dashboard link: https://syzkaller.appspot.com/bug?extid=aad231d51b1923158444
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13b5bb0b400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+aad231...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in sctp_epaddr_lookup_transport+0xacb/0xb20
net/sctp/input.c:971
Read of size 8 at addr ffff8881cde426b0 by task syz-executor3/18110

CPU: 1 PID: 18110 Comm: syz-executor3 Not tainted 4.20.0-rc2+ #187
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+0x244/0x39d lib/dump_stack.c:113
print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
sctp_epaddr_lookup_transport+0xacb/0xb20 net/sctp/input.c:971
sctp_endpoint_lookup_assoc+0xe0/0x290 net/sctp/endpointola.c:338
sctp_addr_id2transport+0x1f8/0x370 net/sctp/socket.c:279
sctp_getsockopt_peer_addr_params+0x17c/0x1260 net/sctp/socket.c:5613
sctp_getsockopt+0x44f9/0x7d32 net/sctp/socket.c:7462
sock_common_getsockopt+0x9a/0xe0 net/core/sock.c:2937
__sys_getsockopt+0x1ad/0x390 net/socket.c:1939
__do_sys_getsockopt net/socket.c:1950 [inline]
__se_sys_getsockopt net/socket.c:1947 [inline]
__x64_sys_getsockopt+0xbe/0x150 net/socket.c:1947
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457569
Code: fd b3 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 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f177b561c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000457569
RDX: 0000000000000009 RSI: 0000000000000084 RDI: 0000000000000006
RBP: 000000000072c180 R08: 000000002044fffc R09: 0000000000000000
R10: 0000000020a68000 R11: 0000000000000246 R12: 00007f177b5626d4
R13: 00000000004c8318 R14: 00000000004ce200 R15: 00000000ffffffff

Allocated by task 18068:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
kmem_cache_alloc_trace+0x152/0x750 mm/slab.c:3620
kmalloc include/linux/slab.h:546 [inline]
kzalloc include/linux/slab.h:741 [inline]
sctp_association_new+0x14e/0x2290 net/sctp/associola.c:311
sctp_sendmsg_new_asoc+0x39c/0x11f0 net/sctp/socket.c:1723
sctp_sendmsg+0x18a5/0x1da0 net/sctp/socket.c:2086
inet_sendmsg+0x1a1/0x690 net/ipv4/af_inet.c:798
sock_sendmsg_nosec net/socket.c:621 [inline]
sock_sendmsg+0xd5/0x120 net/socket.c:631
__sys_sendto+0x3d7/0x670 net/socket.c:1788
__do_sys_sendto net/socket.c:1800 [inline]
__se_sys_sendto net/socket.c:1796 [inline]
__x64_sys_sendto+0xe1/0x1a0 net/socket.c:1796
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 18110:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
__cache_free mm/slab.c:3498 [inline]
kfree+0xcf/0x230 mm/slab.c:3817
sctp_association_destroy net/sctp/associola.c:437 [inline]
sctp_association_put+0x264/0x350 net/sctp/associola.c:889
sctp_transport_destroy net/sctp/transport.c:180 [inline]
sctp_transport_put+0x186/0x1f0 net/sctp/transport.c:340
sctp_hash_cmp+0x1ef/0x260 net/sctp/input.c:825
__rhashtable_lookup include/linux/rhashtable.h:483 [inline]
rhltable_lookup include/linux/rhashtable.h:566 [inline]
sctp_epaddr_lookup_transport+0x4fe/0xb20 net/sctp/input.c:967
sctp_endpoint_lookup_assoc+0xe0/0x290 net/sctp/endpointola.c:338
sctp_addr_id2transport+0x1f8/0x370 net/sctp/socket.c:279
sctp_getsockopt_peer_addr_params+0x17c/0x1260 net/sctp/socket.c:5613
sctp_getsockopt+0x44f9/0x7d32 net/sctp/socket.c:7462
sock_common_getsockopt+0x9a/0xe0 net/core/sock.c:2937
__sys_getsockopt+0x1ad/0x390 net/socket.c:1939
__do_sys_getsockopt net/socket.c:1950 [inline]
__se_sys_getsockopt net/socket.c:1947 [inline]
__x64_sys_getsockopt+0xbe/0x150 net/socket.c:1947
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8881cde42600
which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 176 bytes inside of
4096-byte region [ffff8881cde42600, ffff8881cde43600)
The buggy address belongs to the page:
page:ffffea0007379080 count:1 mapcount:0 mapping:ffff8881da800dc0 index:0x0
compound_mapcount: 0
flags: 0x2fffc0000010200(slab|head)
raw: 02fffc0000010200 ffffea0007379008 ffffea0007377f08 ffff8881da800dc0
raw: 0000000000000000 ffff8881cde42600 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8881cde42580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8881cde42600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8881cde42680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8881cde42700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8881cde42780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
kobject: 'loop5' (00000000f0e4ffac): fill_kobj_path: path
= '/devices/virtual/block/loop5'


---
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[Xin Long]

On Sat, Nov 17, 2018 at 10:59 AM syzbot
<syzbot+aad231...@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: a97b95653383 drivers/net/ethernet/qlogic/qed/qed_rdma.h: f..
> git tree: net
> console output: https://syzkaller.appspot.com/x/log.txt?x=1217d26d400000
> kernel config: https://syzkaller.appspot.com/x/.config?x=d86f24333880b605
> dashboard link: https://syzkaller.appspot.com/bug?extid=aad231d51b1923158444
> compiler: gcc (GCC) 8.0.1 20180413 (experimental)
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13b5bb0b400000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+aad231...@syzkaller.appspotmail.com
>
> ==================================================================
> BUG: KASAN: use-after-free in sctp_epaddr_lookup_transport+0xacb/0xb20
> net/sctp/input.c:971
> Read of size 8 at addr ffff8881cde426b0 by task syz-executor3/18110
>

The same fix is needed in sctp_epaddr_lookup_transport() as:
commit bab1be79a5169ac748d8292b20c86d874022d7ba
Author: Xin Long <lucie...@gmail.com>
Date: Mon Aug 27 18:38:31 2018 +0800

sctp: hold transport before accessing its asoc in sctp_transport_get_next