bisecting fixing commit since 961f830af0658ef5ef8a7708786d634a6115f16b
building syzkaller on ff51e5229e0ee846d2fd687cb0dbca13de758c66
testing commit 961f830af0658ef5ef8a7708786d634a6115f16b with gcc (GCC) 8.4.1 20210217
kernel signature: da6d44440e9daf7f73a64c3e4903ec344307fd6758112101108e65cdbb494b85
all runs: crashed: KASAN: use-after-free Read in vlan_dev_get_iflink
testing current HEAD 1e986fe9ad15b8406034c504afc5ae76f0a8e852
testing commit 1e986fe9ad15b8406034c504afc5ae76f0a8e852 with gcc (GCC) 8.4.1 20210217
kernel signature: de4d87862b915f4b8689ae0c9f3d807f658eeb07b349b860521614c34fa7e92d
all runs: crashed: KASAN: use-after-free Read in vlan_dev_get_iflink
revisions tested: 2, total time: 29m32.619155156s (build: 21m10.772368184s, test: 7m47.59737187s)
the crash still happens on HEAD
commit msg: Linux 4.19.191
crash: KASAN: use-after-free Read in vlan_dev_get_iflink
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.2'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.4'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.3'.
==================================================================
BUG: KASAN: use-after-free in vlan_dev_get_iflink+0x5f/0x70 net/8021q/vlan_dev.c:771
Read of size 4 at addr ffff8881dfd40f48 by task syz-executor.3/23373

CPU: 0 PID: 23373 Comm: syz-executor.3 Not tainted 4.19.191-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+0x17c/0x226 lib/dump_stack.c:118
 print_address_description.cold.6+0x9/0x211 mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report mm/kasan/report.c:412 [inline]
 kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:396
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
 vlan_dev_get_iflink+0x5f/0x70 net/8021q/vlan_dev.c:771
 dev_get_iflink+0x65/0xb0 net/core/dev.c:692
 rfc2863_policy+0x185/0x240 net/core/link_watch.c:43
 linkwatch_do_dev+0x12/0xc0 net/core/link_watch.c:157
 linkwatch_forget_dev+0x14f/0x1f0 net/core/link_watch.c:223
 netdev_wait_allrefs net/core/dev.c:8884 [inline]
 netdev_run_todo+0x222/0x690 net/core/dev.c:8980
 rtnl_unlock net/core/rtnetlink.c:117 [inline]
 rtnetlink_rcv_msg+0x357/0x950 net/core/rtnetlink.c:4779
 netlink_rcv_skb+0x13e/0x3d0 net/netlink/af_netlink.c:2455
 rtnetlink_rcv+0x10/0x20 net/core/rtnetlink.c:4796
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x443/0x660 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x667/0xc60 net/netlink/af_netlink.c:1909
 sock_sendmsg_nosec net/socket.c:622 [inline]
 sock_sendmsg+0xac/0xf0 net/socket.c:632
 ___sys_sendmsg+0x647/0x950 net/socket.c:2115
 __sys_sendmsg+0xd9/0x180 net/socket.c:2153
 __do_sys_sendmsg net/socket.c:2162 [inline]
 __se_sys_sendmsg net/socket.c:2160 [inline]
 __x64_sys_sendmsg+0x73/0xb0 net/socket.c:2160
 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x464909
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f86c1652188 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 000000000055bf00 RCX: 0000000000464909
RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000003
RBP: 00000000004ae620 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000055bf00
R13: 00007ffd3b8ebc0f R14: 00007f86c1652300 R15: 0000000000022000

Allocated by task 23373:
 save_stack mm/kasan/kasan.c:448 [inline]
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc.part.1+0x62/0xf0 mm/kasan/kasan.c:553
 kasan_kmalloc+0xaf/0xc0 mm/kasan/kasan.c:538
 __do_kmalloc_node mm/slab.c:3689 [inline]
 __kmalloc_node+0x50/0x70 mm/slab.c:3696
 kmalloc_node include/linux/slab.h:557 [inline]
 kvmalloc_node+0x68/0x70 mm/util.c:423
 kvmalloc include/linux/mm.h:577 [inline]
 kvzalloc include/linux/mm.h:585 [inline]
 alloc_netdev_mqs+0x5d/0xc80 net/core/dev.c:9144
 rtnl_create_link+0x1a8/0xac0 net/core/rtnetlink.c:2869
 rtnl_newlink+0xbf8/0x1360 net/core/rtnetlink.c:3131
 rtnetlink_rcv_msg+0x34f/0x950 net/core/rtnetlink.c:4778
 netlink_rcv_skb+0x13e/0x3d0 net/netlink/af_netlink.c:2455
 rtnetlink_rcv+0x10/0x20 net/core/rtnetlink.c:4796
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x443/0x660 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x667/0xc60 net/netlink/af_netlink.c:1909
 sock_sendmsg_nosec net/socket.c:622 [inline]
 sock_sendmsg+0xac/0xf0 net/socket.c:632
 ___sys_sendmsg+0x647/0x950 net/socket.c:2115
 __sys_sendmsg+0xd9/0x180 net/socket.c:2153
 __do_sys_sendmsg net/socket.c:2162 [inline]
 __se_sys_sendmsg net/socket.c:2160 [inline]
 __x64_sys_sendmsg+0x73/0xb0 net/socket.c:2160
 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 23406:
 save_stack mm/kasan/kasan.c:448 [inline]
 set_track mm/kasan/kasan.c:460 [inline]
 __kasan_slab_free+0x13c/0x220 mm/kasan/kasan.c:521
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
 __cache_free mm/slab.c:3503 [inline]
 kfree+0xcf/0x220 mm/slab.c:3822
 kvfree+0x2c/0x30 mm/util.c:452
 netdev_freemem+0x47/0x60 net/core/dev.c:9098
 netdev_release+0x6c/0x90 net/core/net-sysfs.c:1695
 device_release+0x71/0x1d0 drivers/base/core.c:1076
 kobject_cleanup lib/kobject.c:662 [inline]
 kobject_release lib/kobject.c:691 [inline]
 kref_put include/linux/kref.h:70 [inline]
 kobject_put+0x115/0x1f0 lib/kobject.c:708
 netdev_run_todo+0x459/0x690 net/core/dev.c:9003
 rtnl_unlock net/core/rtnetlink.c:117 [inline]
 rtnetlink_rcv_msg+0x357/0x950 net/core/rtnetlink.c:4779
 netlink_rcv_skb+0x13e/0x3d0 net/netlink/af_netlink.c:2455
 rtnetlink_rcv+0x10/0x20 net/core/rtnetlink.c:4796
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x443/0x660 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x667/0xc60 net/netlink/af_netlink.c:1909
 sock_sendmsg_nosec net/socket.c:622 [inline]
 sock_sendmsg+0xac/0xf0 net/socket.c:632
 ___sys_sendmsg+0x647/0x950 net/socket.c:2115
 __sys_sendmsg+0xd9/0x180 net/socket.c:2153
 __do_sys_sendmsg net/socket.c:2162 [inline]
 __se_sys_sendmsg net/socket.c:2160 [inline]
 __x64_sys_sendmsg+0x73/0xb0 net/socket.c:2160
 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8881dfd40e40
 which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 264 bytes inside of
 4096-byte region [ffff8881dfd40e40, ffff8881dfd41e40)
The buggy address belongs to the page:
page:ffffea00077f5000 count:1 mapcount:0 mapping:ffff8881f6400dc0 index:0x0 compound_mapcount: 0
flags: 0x17ffe0000008100(slab|head)
raw: 017ffe0000008100 ffffea0007a56588 ffffea00079cbc88 ffff8881f6400dc0
raw: 0000000000000000 ffff8881dfd40e40 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881dfd40e00: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
 ffff8881dfd40e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881dfd40f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                              ^
 ffff8881dfd40f80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881dfd41000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
nla_parse: 121 callbacks suppressed
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.1'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.4'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.0'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.3'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.2'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.5'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.4'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.1'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.0'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.3'.
nla_parse: 150 callbacks suppressed
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.5'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.1'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.2'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.4'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.3'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.0'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.5'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.1'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.2'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor.3'.