KASAN: use-after-free Read in tipc_mcast_xmit

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 8203e2d844d3 net: clear skb->tstamp in forwarding paths
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=17d37c1b400000
kernel config: https://syzkaller.appspot.com/x/.config?x=c8970c89a0efbb23
dashboard link: https://syzkaller.appspot.com/bug?extid=99f20222fc5018d2b97a
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10d7c943400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+99f202...@syzkaller.appspotmail.com

IPv6: ADDRCONF(NETDEV_UP): veth1: link is not ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
8021q: adding VLAN 0 to HW filter on device team0
==================================================================
BUG: KASAN: use-after-free in tipc_mcast_xmit+0xb77/0xdb0
net/tipc/bcast.c:305
Read of size 1 at addr ffff8881d219454e by task syz-executor0/6307

CPU: 0 PID: 6307 Comm: syz-executor0 Not tainted 4.20.0-rc6+ #234
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_load1_noabort+0x14/0x20 mm/kasan/report.c:430
tipc_mcast_xmit+0xb77/0xdb0 net/tipc/bcast.c:305
tipc_send_group_bcast+0xa5f/0xdf0 net/tipc/socket.c:1054
__tipc_sendmsg+0xeec/0x1d40 net/tipc/socket.c:1310
tipc_sendmsg+0x50/0x70 net/tipc/socket.c:1275
sock_sendmsg_nosec net/socket.c:621 [inline]
sock_sendmsg+0xd5/0x120 net/socket.c:631
___sys_sendmsg+0x7fd/0x930 net/socket.c:2116
__sys_sendmsg+0x11d/0x280 net/socket.c:2154
__do_sys_sendmsg net/socket.c:2163 [inline]
__se_sys_sendmsg net/socket.c:2161 [inline]
__x64_sys_sendmsg+0x78/0xb0 net/socket.c:2161
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457669
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:00007fbfc19b2c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457669
RDX: 0000000000000000 RSI: 00000000200001c0 RDI: 0000000000000004
RBP: 000000000072bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fbfc19b36d4
R13: 00000000004c44bd R14: 00000000004d74a8 R15: 00000000ffffffff

Allocated by task 6307:
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]
tipc_group_create+0x152/0xa70 net/tipc/group.c:171
tipc_sk_join net/tipc/socket.c:2836 [inline]
tipc_setsockopt+0x2d1/0xd70 net/tipc/socket.c:2951
__sys_setsockopt+0x1ba/0x3c0 net/socket.c:1902
__do_sys_setsockopt net/socket.c:1913 [inline]
__se_sys_setsockopt net/socket.c:1910 [inline]
__x64_sys_setsockopt+0xbe/0x150 net/socket.c:1910
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 6308:
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
tipc_group_delete+0x2e4/0x3f0 net/tipc/group.c:227
tipc_sk_leave+0x113/0x220 net/tipc/socket.c:2870
tipc_setsockopt+0x97d/0xd70 net/tipc/socket.c:2954
__sys_setsockopt+0x1ba/0x3c0 net/socket.c:1902
__do_sys_setsockopt net/socket.c:1913 [inline]
__se_sys_setsockopt net/socket.c:1910 [inline]
__x64_sys_setsockopt+0xbe/0x150 net/socket.c:1910
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 ffff8881d2194500
which belongs to the cache kmalloc-192 of size 192
The buggy address is located 78 bytes inside of
192-byte region [ffff8881d2194500, ffff8881d21945c0)
The buggy address belongs to the page:
page:ffffea0007486500 count:1 mapcount:0 mapping:ffff8881da800040 index:0x0
flags: 0x2fffc0000000200(slab)
raw: 02fffc0000000200 ffffea00074e6dc8 ffffea000748fa88 ffff8881da800040
raw: 0000000000000000 ffff8881d2194000 0000000100000010 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8881d2194400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8881d2194480: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
> ffff8881d2194500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8881d2194580: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff8881d2194600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


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[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger
crash:

Reported-and-tested-by:
syzbot+99f202...@syzkaller.appspotmail.com

Tested on:

commit: d4fa88f3c276 tipc: check group dests after tipc_wait_for_c..
git tree: https://github.com/congwang/linux.git tipc
kernel config: https://syzkaller.appspot.com/x/.config?x=c8970c89a0efbb23

compiler: gcc (GCC) 8.0.1 20180413 (experimental)

Note: testing is done by a robot and is best-effort only.