bisecting fixing commit since 4a94c43323342f1522034d6566c5129a7386a0ab
building syzkaller on 36650b4b2c942bc382314dce384d311fbadd1208
testing commit 4a94c43323342f1522034d6566c5129a7386a0ab with gcc (GCC) 8.1.0
kernel signature: 65ed2f9e05ae1adeb86c6eb8c62cca38a8809ea906cf73f6990c7f3e94d17580
run #0: crashed: KASAN: use-after-free Read in eth_type_trans
run #1: crashed: KASAN: use-after-free Read in eth_type_trans
run #2: crashed: KASAN: slab-out-of-bounds Read in eth_type_trans
run #3: crashed: KASAN: use-after-free Read in eth_type_trans
run #4: crashed: KASAN: use-after-free Read in eth_type_trans
run #5: crashed: KASAN: use-after-free Read in eth_type_trans
run #6: crashed: KASAN: use-after-free Read in eth_type_trans
run #7: crashed: KASAN: use-after-free Read in eth_type_trans
run #8: crashed: KASAN: use-after-free Read in eth_type_trans
run #9: crashed: KASAN: use-after-free Read in eth_type_trans
testing current HEAD 24085f70a6e1b0cb647ec92623284641d8270637
testing commit 24085f70a6e1b0cb647ec92623284641d8270637 with gcc (GCC) 8.1.0
kernel signature: 30e0823987a6aaee0ee1f4094e2447ebbcb30f4e47c05d989815548992be4fd7
all runs: crashed: KASAN: use-after-free Read in eth_type_trans
revisions tested: 2, total time: 19m12.430484422s (build: 12m0.215076008s, test: 6m13.067168804s)
the crash still happens on HEAD
commit msg: Merge tag 'trace-v5.7-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
crash: KASAN: use-after-free Read in eth_type_trans
==================================================================
BUG: KASAN: use-after-free in ether_addr_equal_64bits include/linux/etherdevice.h:347 [inline]
BUG: KASAN: use-after-free in eth_type_trans+0x601/0x740 net/ethernet/eth.c:167
Read of size 8 at addr ffff8880797f0040 by task syz-executor.1/7990

CPU: 0 PID: 7990 Comm: syz-executor.1 Not tainted 5.7.0-rc5-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+0x12d/0x187 lib/dump_stack.c:118
 print_address_description.constprop.8.cold.10+0x9/0x31d mm/kasan/report.c:382
 __kasan_report.cold.11+0x37/0x4e mm/kasan/report.c:511
 kasan_report+0x38/0x50 mm/kasan/common.c:625
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:146
 ether_addr_equal_64bits include/linux/etherdevice.h:347 [inline]
 eth_type_trans+0x601/0x740 net/ethernet/eth.c:167
 napi_frags_finish net/core/dev.c:5963 [inline]
 napi_gro_frags+0x6da/0xb00 net/core/dev.c:6038
 tun_get_user+0x2609/0x3a70 drivers/net/tun.c:1946
 tun_chr_write_iter+0xb5/0x156 drivers/net/tun.c:1992
 call_write_iter include/linux/fs.h:1907 [inline]
 do_iter_readv_writev+0x532/0xa70 fs/read_write.c:694
 do_iter_write+0x130/0x510 fs/read_write.c:999
 vfs_writev+0x16d/0x2d0 fs/read_write.c:1072
 do_writev+0x118/0x2e0 fs/read_write.c:1115
 __do_sys_writev fs/read_write.c:1188 [inline]
 __se_sys_writev fs/read_write.c:1185 [inline]
 __x64_sys_writev+0x70/0xb0 fs/read_write.c:1185
 do_syscall_64+0xca/0x630 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3
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:00007f606f354ba0 EFLAGS: 00000293 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 0000000000207843 RCX: 000000000045a7d1
RDX: 0000000000000001 RSI: 00007f606f354c00 RDI: 00000000000000f0
RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000
R10: 00007f606f3559d0 R11: 0000000000000293 R12: 00007f606f3556d4
R13: 00000000004cab1f R14: 00000000004e4040 R15: 00000000ffffffff

The buggy address belongs to the page:
page:ffffea0001e5fc00 refcount:0 mapcount:0 mapping:00000000a3cb0c44 index:0x0
flags: 0xfffe0000000000()
raw: 00fffe0000000000 ffffea0001e5fc08 ffffea0001e5fc08 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880797eff00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8880797eff80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8880797f0000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                           ^
 ffff8880797f0080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8880797f0100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================