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SubjectKASAN: use-after-free Read in br_mdb_ip_get
From
Hello,

syzbot found the following crash on:

HEAD commit: ba6069759381 Merge tag 'mmc-v5.0-rc2' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17b342c4c00000
kernel config: https://syzkaller.appspot.com/x/.config?x=505743eba4e4f68
dashboard link: https://syzkaller.appspot.com/bug?extid=bc5ab0af2dbf3b0ae897
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+bc5ab0af2dbf3b0ae897@syzkaller.appspotmail.com

bridge0: port 2(bridge_slave_1) entered blocking state
bridge0: port 2(bridge_slave_1) entered forwarding state
bridge0: port 1(bridge_slave_0) entered blocking state
bridge0: port 1(bridge_slave_0) entered forwarding state
==================================================================
BUG: KASAN: use-after-free in memcmp+0xb3/0xc0 lib/string.c:862
Read of size 1 at addr ffff88809f1efe70 by task syz-executor1/8111

CPU: 0 PID: 8111 Comm: syz-executor1 Not tainted 5.0.0-rc3+ #43
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
<IRQ>
__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
IPv6: ADDRCONF(NETDEV_UP): bond0: link is not ready
kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
8021q: adding VLAN 0 to HW filter on device bond0
__asan_report_load1_noabort+0x14/0x20 mm/kasan/generic_report.c:132
memcmp+0xb3/0xc0 lib/string.c:862
memcmp include/linux/string.h:393 [inline]
rhashtable_compare include/linux/rhashtable.h:473 [inline]
__rhashtable_lookup include/linux/rhashtable.h:498 [inline]
rhashtable_lookup include/linux/rhashtable.h:534 [inline]
br_mdb_ip_get+0x694/0xe30 net/bridge/br_multicast.c:97
IPv6: ADDRCONF(NETDEV_UP): veth0: link is not ready
br_multicast_new_group+0x77/0x200 net/bridge/br_multicast.c:467
IPv6: ADDRCONF(NETDEV_UP): team0: link is not ready
8021q: adding VLAN 0 to HW filter on device team0
br_multicast_add_group+0x4ce/0x7d0 net/bridge/br_multicast.c:552
br_ip6_multicast_add_group net/bridge/br_multicast.c:626 [inline]
br_ip6_multicast_mld2_report net/bridge/br_multicast.c:1043 [inline]
br_multicast_ipv6_rcv net/bridge/br_multicast.c:1667 [inline]
br_multicast_rcv+0x24aa/0x4270 net/bridge/br_multicast.c:1705
IPv6: ADDRCONF(NETDEV_UP): hsr0: link is not ready
IPv6: ADDRCONF(NETDEV_CHANGE): hsr0: link becomes ready
IPv6: ADDRCONF(NETDEV_UP): vxcan1: link is not ready
br_dev_xmit+0x7f4/0x1780 net/bridge/br_device.c:93
8021q: adding VLAN 0 to HW filter on device batadv0
__netdev_start_xmit include/linux/netdevice.h:4382 [inline]
netdev_start_xmit include/linux/netdevice.h:4391 [inline]
xmit_one net/core/dev.c:3278 [inline]
dev_hard_start_xmit+0x261/0xc70 net/core/dev.c:3294
__dev_queue_xmit+0x2f8a/0x3a60 net/core/dev.c:3864
dev_queue_xmit+0x18/0x20 net/core/dev.c:3897
neigh_hh_output include/net/neighbour.h:498 [inline]
neigh_output include/net/neighbour.h:506 [inline]
ip6_finish_output2+0x141a/0x28e0 net/ipv6/ip6_output.c:120
ip6_finish_output+0x577/0xc30 net/ipv6/ip6_output.c:154
NF_HOOK_COND include/linux/netfilter.h:278 [inline]
ip6_output+0x23c/0xa00 net/ipv6/ip6_output.c:171
dst_output include/net/dst.h:444 [inline]
NF_HOOK include/linux/netfilter.h:289 [inline]
NF_HOOK include/linux/netfilter.h:283 [inline]
mld_sendpack+0xa44/0xfd0 net/ipv6/mcast.c:1683
mld_send_cr net/ipv6/mcast.c:1979 [inline]
mld_ifc_timer_expire+0x449/0x8a0 net/ipv6/mcast.c:2478
call_timer_fn+0x254/0x900 kernel/time/timer.c:1325
expire_timers kernel/time/timer.c:1362 [inline]
__run_timers+0x6fc/0xd50 kernel/time/timer.c:1681
run_timer_softirq+0x52/0xb0 kernel/time/timer.c:1694
__do_softirq+0x30b/0xb11 kernel/softirq.c:292
invoke_softirq kernel/softirq.c:373 [inline]
irq_exit+0x180/0x1d0 kernel/softirq.c:413
exiting_irq arch/x86/include/asm/apic.h:536 [inline]
smp_apic_timer_interrupt+0x1b7/0x760 arch/x86/kernel/apic/apic.c:1062
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:807
</IRQ>
RIP: 0010:kasan_check_read+0x0/0x20 mm/kasan/common.c:99
Code: ef e9 14 eb ff ff 48 8b 73 58 89 c2 48 c7 c7 f0 c2 3c 89 f7 da e8 54
69 a2 ff e9 c4 f5 ff ff 90 90 90 90 90 90 90 90 90 90 90 <55> 89 f6 31 d2
48 89 e5 48 8b 4d 08 e8 ff 23 00 00 5d c3 0f 1f 00
IPVS: ftp: loaded support on port[0] = 21
RSP: 0018:ffff88809e937428 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: 0000000000000000 RBX: ffffffff8a318400 RCX: ffffffff8162f642
RDX: 0000000000000001 RSI: 0000000000000008 RDI: ffffffff8a318400
RBP: ffff88809e937530 R08: 1ffffffff1463080 R09: fffffbfff1463081
R10: fffffbfff1463080 R11: ffffffff8a318407 R12: ffff88809ac4c600
R13: ffff88809e937508 R14: dffffc0000000000 R15: ffffed1013d26e91
mutex_optimistic_spin kernel/locking/mutex.c:646 [inline]
__mutex_lock_common kernel/locking/mutex.c:928 [inline]
__mutex_lock+0x377/0x1670 kernel/locking/mutex.c:1072
IPVS: ftp: loaded support on port[0] = 21
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087
rtnl_lock net/core/rtnetlink.c:77 [inline]
rtnetlink_rcv_msg+0x425/0xc30 net/core/rtnetlink.c:5127
netlink_rcv_skb+0x17d/0x410 net/netlink/af_netlink.c:2477
rtnetlink_rcv+0x1d/0x30 net/core/rtnetlink.c:5148
netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline]
netlink_unicast+0x574/0x770 net/netlink/af_netlink.c:1336
netlink_sendmsg+0xa05/0xf90 net/netlink/af_netlink.c:1917
sock_sendmsg_nosec net/socket.c:621 [inline]
sock_sendmsg+0xdd/0x130 net/socket.c:631
__sys_sendto+0x387/0x5f0 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+0x1a3/0x800 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x411fc3
Code: ff 0f 83 40 18 00 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00
83 3d cd 42 64 00 00 75 17 49 89 ca b8 2c 00 00 00 0f 05 <48> 3d 01 f0 ff
ff 0f 83 11 18 00 00 c3 48 83 ec 08 e8 87 fa ff ff
RSP: 002b:0000000000a4fb28 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000411fc3
RDX: 000000000000006c RSI: 0000000000a50070 RDI: 0000000000000003
RBP: 0000000000000003 R08: 0000000000a4fb30 R09: 000000000000000c
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000a4fef0
R13: 0000000000a4fbb8 R14: 0000000000a4fc80 R15: 00000000004bcf8a

Allocated by task 8111:
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
kmem_cache_alloc_trace+0x151/0x760 mm/slab.c:3609
kmalloc include/linux/slab.h:545 [inline]
kzalloc include/linux/slab.h:740 [inline]
br_multicast_new_group.part.0+0xdc/0x1a40 net/bridge/br_multicast.c:476
br_multicast_new_group+0x19d/0x200 net/bridge/br_multicast.c:471
br_multicast_add_group+0x4ce/0x7d0 net/bridge/br_multicast.c:552
br_ip6_multicast_add_group net/bridge/br_multicast.c:626 [inline]
br_ip6_multicast_mld2_report net/bridge/br_multicast.c:1043 [inline]
br_multicast_ipv6_rcv net/bridge/br_multicast.c:1667 [inline]
br_multicast_rcv+0x24aa/0x4270 net/bridge/br_multicast.c:1705
br_dev_xmit+0x7f4/0x1780 net/bridge/br_device.c:93
__netdev_start_xmit include/linux/netdevice.h:4382 [inline]
netdev_start_xmit include/linux/netdevice.h:4391 [inline]
xmit_one net/core/dev.c:3278 [inline]
dev_hard_start_xmit+0x261/0xc70 net/core/dev.c:3294
__dev_queue_xmit+0x2f8a/0x3a60 net/core/dev.c:3864
dev_queue_xmit+0x18/0x20 net/core/dev.c:3897
neigh_resolve_output net/core/neighbour.c:1476 [inline]
neigh_resolve_output+0x6a0/0xb30 net/core/neighbour.c:1456
neigh_output include/net/neighbour.h:508 [inline]
ip6_finish_output2+0xc56/0x28e0 net/ipv6/ip6_output.c:120
ip6_finish_output+0x577/0xc30 net/ipv6/ip6_output.c:154
NF_HOOK_COND include/linux/netfilter.h:278 [inline]
ip6_output+0x23c/0xa00 net/ipv6/ip6_output.c:171
dst_output include/net/dst.h:444 [inline]
NF_HOOK include/linux/netfilter.h:289 [inline]
NF_HOOK include/linux/netfilter.h:283 [inline]
mld_sendpack+0xa44/0xfd0 net/ipv6/mcast.c:1683
mld_send_cr net/ipv6/mcast.c:1979 [inline]
mld_ifc_timer_expire+0x449/0x8a0 net/ipv6/mcast.c:2478
call_timer_fn+0x254/0x900 kernel/time/timer.c:1325
expire_timers kernel/time/timer.c:1362 [inline]
__run_timers+0x6fc/0xd50 kernel/time/timer.c:1681
run_timer_softirq+0x52/0xb0 kernel/time/timer.c:1694
__do_softirq+0x30b/0xb11 kernel/softirq.c:292

Freed by task 8111:
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
br_multicast_new_group.part.0+0x1489/0x1a40 net/bridge/br_multicast.c:486
br_multicast_new_group+0x19d/0x200 net/bridge/br_multicast.c:471
br_multicast_add_group+0x4ce/0x7d0 net/bridge/br_multicast.c:552
br_ip6_multicast_add_group net/bridge/br_multicast.c:626 [inline]
br_ip6_multicast_mld2_report net/bridge/br_multicast.c:1043 [inline]
br_multicast_ipv6_rcv net/bridge/br_multicast.c:1667 [inline]
br_multicast_rcv+0x24aa/0x4270 net/bridge/br_multicast.c:1705
br_dev_xmit+0x7f4/0x1780 net/bridge/br_device.c:93
__netdev_start_xmit include/linux/netdevice.h:4382 [inline]
netdev_start_xmit include/linux/netdevice.h:4391 [inline]
xmit_one net/core/dev.c:3278 [inline]
dev_hard_start_xmit+0x261/0xc70 net/core/dev.c:3294
__dev_queue_xmit+0x2f8a/0x3a60 net/core/dev.c:3864
dev_queue_xmit+0x18/0x20 net/core/dev.c:3897
neigh_resolve_output net/core/neighbour.c:1476 [inline]
neigh_resolve_output+0x6a0/0xb30 net/core/neighbour.c:1456
neigh_output include/net/neighbour.h:508 [inline]
ip6_finish_output2+0xc56/0x28e0 net/ipv6/ip6_output.c:120
ip6_finish_output+0x577/0xc30 net/ipv6/ip6_output.c:154
NF_HOOK_COND include/linux/netfilter.h:278 [inline]
ip6_output+0x23c/0xa00 net/ipv6/ip6_output.c:171
dst_output include/net/dst.h:444 [inline]
NF_HOOK include/linux/netfilter.h:289 [inline]
NF_HOOK include/linux/netfilter.h:283 [inline]
mld_sendpack+0xa44/0xfd0 net/ipv6/mcast.c:1683
mld_send_cr net/ipv6/mcast.c:1979 [inline]
mld_ifc_timer_expire+0x449/0x8a0 net/ipv6/mcast.c:2478
call_timer_fn+0x254/0x900 kernel/time/timer.c:1325
expire_timers kernel/time/timer.c:1362 [inline]
__run_timers+0x6fc/0xd50 kernel/time/timer.c:1681
run_timer_softirq+0x52/0xb0 kernel/time/timer.c:1694
__do_softirq+0x30b/0xb11 kernel/softirq.c:292

The buggy address belongs to the object at ffff88809f1efe00
which belongs to the cache kmalloc-192 of size 192
The buggy address is located 112 bytes inside of
192-byte region [ffff88809f1efe00, ffff88809f1efec0)
The buggy address belongs to the page:
page:ffffea00027c7bc0 count:1 mapcount:0 mapping:ffff88812c3f0040 index:0x0
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea00027df108 ffffea00027c7c48 ffff88812c3f0040
raw: 0000000000000000 ffff88809f1ef000 0000000100000010 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88809f1efd00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88809f1efd80: 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff88809f1efe00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88809f1efe80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff88809f1eff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
syzbot.

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