bisecting fixing commit since 7d120bf21c05cbe30a679f0feeca884eeaceb069
building syzkaller on 79b211f74b08737aeb4934c6ff69a263b3c38013
testing commit 7d120bf21c05cbe30a679f0feeca884eeaceb069 with gcc (GCC) 8.1.0
kernel signature: 3be8dd4d75a095181f4f05ef2a6e1e05542d2efc
all runs: crashed: KASAN: use-after-free Read in eth_type_trans
testing current HEAD dc4ba5be1babd3b3ec905751a30df89a5899a7a9
testing commit dc4ba5be1babd3b3ec905751a30df89a5899a7a9 with gcc (GCC) 8.1.0
kernel signature: b0e120efdda4bddc69579c0fce9da796db3b578d
all runs: crashed: KASAN: use-after-free Read in eth_type_trans
revisions tested: 2, total time: 25m16.654882997s (build: 17m57.657844707s, test: 6m20.726021905s)
the crash still happens on HEAD
commit msg: Linux 4.19.97
crash: KASAN: use-after-free Read in eth_type_trans
IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
IPv6: ADDRCONF(NETDEV_UP): veth0_to_bond: link is not ready
==================================================================
IPv6: ADDRCONF(NETDEV_UP): veth0_to_bridge: link is not ready
BUG: KASAN: use-after-free in is_multicast_ether_addr_64bits include/linux/etherdevice.h:139 [inline]
BUG: KASAN: use-after-free in eth_type_trans+0x5c1/0x6e0 net/ethernet/eth.c:168
IPv6: ADDRCONF(NETDEV_UP): veth1_to_bridge: link is not ready
Read of size 8 at addr ffff888076bf0040 by task syz-executor.0/7343

CPU: 0 PID: 7343 Comm: syz-executor.0 Not tainted 4.19.97-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+0x123/0x177 lib/dump_stack.c:118
 print_address_description.cold.8+0x9/0x1ff mm/kasan/report.c:256
IPv6: ADDRCONF(NETDEV_UP): veth0_to_bond: link is not ready
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.9+0x242/0x309 mm/kasan/report.c:412
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 is_multicast_ether_addr_64bits include/linux/etherdevice.h:139 [inline]
 eth_type_trans+0x5c1/0x6e0 net/ethernet/eth.c:168
 napi_frags_finish net/core/dev.c:5704 [inline]
 napi_gro_frags+0x546/0x8e0 net/core/dev.c:5778
 tun_get_user+0x25ef/0x4780 drivers/net/tun.c:1939
 tun_chr_write_iter+0xaf/0x150 drivers/net/tun.c:1985
 call_write_iter include/linux/fs.h:1820 [inline]
 do_iter_readv_writev+0x4ae/0x960 fs/read_write.c:681
IPv6: ADDRCONF(NETDEV_UP): veth1_to_bond: link is not ready
 do_iter_write+0x12a/0x510 fs/read_write.c:960
 vfs_writev+0x16f/0x2d0 fs/read_write.c:1005
 do_writev+0x110/0x330 fs/read_write.c:1040
 __do_sys_writev fs/read_write.c:1113 [inline]
 __se_sys_writev fs/read_write.c:1110 [inline]
 __x64_sys_writev+0x70/0xb0 fs/read_write.c:1110
 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45a7d1
Code: 75 14 b8 14 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 e4 b7 fb ff c3 48 83 ec 08 e8 fa 2c 00 00 48 89 04 24 b8 14 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 43 2d 00 00 48 89 d0 48 83 c4 08 48 3d 01
RSP: 002b:00007f5a6cfe6ba0 EFLAGS: 00000293 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 0000000000207843 RCX: 000000000045a7d1
RDX: 0000000000000001 RSI: 00007f5a6cfe6c00 RDI: 00000000000000f0
RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000
R10: 00007f5a6cfe79d0 R11: 0000000000000293 R12: 00007f5a6cfe76d4
R13: 00000000004cab1f R14: 00000000004e4040 R15: 00000000ffffffff

The buggy address belongs to the page:
page:ffffea0001dafc00 count:0 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0xfffe0000000000()
raw: 00fffe0000000000 ffffea0001dafc08 ffffea0001dafc08 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888076beff00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888076beff80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888076bf0000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                           ^
 ffff888076bf0080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888076bf0100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================