Subject: Re: KASAN: use-after-free Read in linkwatch_fire_event

From: syzbot <[email-masked]>
Date: Thu, 23 Jul 2020 17:47:14 -0700

syzbot has found a reproducer for the following issue on:

HEAD commit:    4f5baedd Add linux-next specific files for 20200723
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12e497b4900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=785eb1cc9c75f625
dashboard link: https://syzkaller.appspot.com/bug?extid=987da0fff3a594532ce1
compiler:       gcc (GCC) 10.1.0-syz 20200507
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11043454900000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16579f78900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

==================================================================
BUG: KASAN: use-after-free in __list_add_valid+0x93/0xa0 lib/list_debug.c:26
Read of size 8 at addr ffff888065294570 by task syz-executor076/31793
CPU: 1 PID: 31793 Comm: syz-executor076 Not tainted 5.8.0-rc6-next-20200723-syzkaller #0
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+0x18f/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
 __list_add_valid+0x93/0xa0 lib/list_debug.c:26
 __list_add include/linux/list.h:67 [inline]
 list_add_tail include/linux/list.h:100 [inline]
 linkwatch_add_event net/core/link_watch.c:111 [inline]
 linkwatch_fire_event+0xea/0x1d0 net/core/link_watch.c:261
 netif_carrier_off net/sched/sch_generic.c:513 [inline]
 netif_carrier_off+0x96/0xb0 net/sched/sch_generic.c:507
 bond_newlink drivers/net/bonding/bond_netlink.c:460 [inline]
 bond_newlink+0x52/0xa0 drivers/net/bonding/bond_netlink.c:448
 __rtnl_newlink+0x1090/0x1750 net/core/rtnetlink.c:3339
 rtnl_newlink+0x64/0xa0 net/core/rtnetlink.c:3398
 rtnetlink_rcv_msg+0x44e/0xad0 net/core/rtnetlink.c:5461
 netlink_rcv_skb+0x15a/0x430 net/netlink/af_netlink.c:2470
 netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
 netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1330
 netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1919
 sock_sendmsg_nosec net/socket.c:651 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:671
 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2363
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2417
 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2450
 do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x44a979
Code: Bad RIP value.
RSP: 002b:00007f1740ffbd98 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000006e69e8 RCX: 000000000044a979
RDX: 0000000000000000 RSI: 0000000020000040 RDI: 0000000000000004
RBP: 00000000006e69e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006e69ec
R13: 0000000000000000 R14: 0000000000000000 R15: 068500100000003c
Allocated by task 31587:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461
 kmalloc_node include/linux/slab.h:577 [inline]
 kvmalloc_node+0xb4/0xf0 mm/util.c:574
 kvmalloc include/linux/mm.h:760 [inline]
 kvzalloc include/linux/mm.h:768 [inline]
 alloc_netdev_mqs+0x97/0xdc0 net/core/dev.c:9961
 rtnl_create_link+0x219/0xad0 net/core/rtnetlink.c:3067
 __rtnl_newlink+0xfa0/0x1750 net/core/rtnetlink.c:3329
 rtnl_newlink+0x64/0xa0 net/core/rtnetlink.c:3398
 rtnetlink_rcv_msg+0x44e/0xad0 net/core/rtnetlink.c:5461
 netlink_rcv_skb+0x15a/0x430 net/netlink/af_netlink.c:2470
 netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
 netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1330
 netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1919
 sock_sendmsg_nosec net/socket.c:651 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:671
 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2363
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2417
 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2450
 do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
Freed by task 31587:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_set_track+0x1c/0x30 mm/kasan/common.c:56
 kasan_set_free_info+0x1b/0x30 mm/kasan/generic.c:355
 __kasan_slab_free+0xd8/0x120 mm/kasan/common.c:422
 __cache_free mm/slab.c:3418 [inline]
 kfree+0x103/0x2c0 mm/slab.c:3756
 kvfree+0x42/0x50 mm/util.c:603
 device_release+0x71/0x200 drivers/base/core.c:1791
 kobject_cleanup lib/kobject.c:704 [inline]
 kobject_release lib/kobject.c:735 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x171/0x270 lib/kobject.c:752
 put_device+0x1b/0x30 drivers/base/core.c:3020
 free_netdev+0x35d/0x480 net/core/dev.c:10077
 __rtnl_newlink+0x14d8/0x1750 net/core/rtnetlink.c:3354
 rtnl_newlink+0x64/0xa0 net/core/rtnetlink.c:3398
 rtnetlink_rcv_msg+0x44e/0xad0 net/core/rtnetlink.c:5461
 netlink_rcv_skb+0x15a/0x430 net/netlink/af_netlink.c:2470
 netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
 netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1330
 netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1919
 sock_sendmsg_nosec net/socket.c:651 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:671
 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2363
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2417
 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2450
 do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
The buggy address belongs to the object at ffff888065294000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 1392 bytes inside of
 8192-byte region [ffff888065294000, ffff888065296000)
The buggy address belongs to the page:
page:00000000d305b100 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x65294
head:00000000d305b100 order:2 compound_mapcount:0 compound_pincount:0
flags: 0xfffe0000010200(slab|head)
raw: 00fffe0000010200 ffffea000194b708 ffffea00019eb908 ffff8880aa000a00
raw: 0000000000000000 ffff888065294000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
 ffff888065294400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888065294480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888065294500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                             ^
 ffff888065294580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888065294600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================