bisecting fixing commit since 7d80e1218adf6d1aa5270587192789e218fef706
building syzkaller on 6affd8e838ce8a0c7d72445a7f67fe3bde8bbe04
testing commit 7d80e1218adf6d1aa5270587192789e218fef706 with gcc (GCC) 8.1.0
kernel signature: 7034558c7ef61d17439be5c049008691577e0225167681b601d4a3aa95ea8a2a
run #0: crashed: kernel BUG at mm/slab.c:LINE!
run #1: crashed: KASAN: use-after-free Read in bpf_test_finish
run #2: crashed: KASAN: use-after-free Read in bpf_test_finish
run #3: crashed: KASAN: use-after-free Read in bpf_test_finish
run #4: crashed: KASAN: use-after-free Read in bpf_test_finish
run #5: crashed: KASAN: use-after-free Read in bpf_test_finish
run #6: crashed: KASAN: use-after-free Read in bpf_test_finish
run #7: crashed: KASAN: use-after-free Read in bpf_test_finish
run #8: crashed: KASAN: use-after-free Read in corrupted
run #9: crashed: KASAN: use-after-free Read in bpf_test_finish
testing current HEAD ab9dfda232481dcfaf549ce774004d116fc80c13
testing commit ab9dfda232481dcfaf549ce774004d116fc80c13 with gcc (GCC) 8.1.0
kernel signature: 8e97947b54e80c78d322ad66081e6daaf74aa459d8e956fc57669d5d8935f4b0
all runs: crashed: KASAN: use-after-free Read in bpf_test_finish
revisions tested: 2, total time: 25m22.515192562s (build: 17m55.656871625s, test: 5m58.569808716s)
the crash still happens on HEAD
commit msg: Linux 4.14.180
crash: KASAN: use-after-free Read in bpf_test_finish
IPv6: ADDRCONF(NETDEV_CHANGE): bridge0: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_bond: link becomes ready
==================================================================
BUG: KASAN: use-after-free in _copy_to_user+0x84/0xb0 lib/usercopy.c:27
Read of size 931 at addr ffff88807b3ffff3 by task syz-executor.2/7138

CPU: 1 PID: 7138 Comm: syz-executor.2 Not tainted 4.14.180-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0xf7/0x13b lib/dump_stack.c:58
 print_address_description.cold.7+0x9/0x1c9 mm/kasan/report.c:252
IPv6: ADDRCONF(NETDEV_UP): veth0_to_bond: link is not ready
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report.cold.8+0x11a/0x2d3 mm/kasan/report.c:409
 check_memory_region_inline mm/kasan/kasan.c:260 [inline]
 check_memory_region+0x13e/0x1b0 mm/kasan/kasan.c:267
IPv6: ADDRCONF(NETDEV_UP): veth1_to_bond: link is not ready
 kasan_check_read+0x11/0x20 mm/kasan/kasan.c:272
 _copy_to_user+0x84/0xb0 lib/usercopy.c:27
 copy_to_user include/linux/uaccess.h:155 [inline]
 bpf_test_finish.isra.5+0xd5/0x170 net/bpf/test_run.c:59
 bpf_prog_test_run_skb+0x66d/0xbc0 net/bpf/test_run.c:144
 bpf_prog_test_run kernel/bpf/syscall.c:1264 [inline]
 SYSC_bpf kernel/bpf/syscall.c:1529 [inline]
 SyS_bpf+0x4d7/0x288a kernel/bpf/syscall.c:1477
 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x459829
RSP: 002b:00007fd8bd392c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000459829
RDX: 0000000000000028 RSI: 0000000020000140 RDI: 000000000000000a
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fd8bd3936d4
R13: 00000000004bfb92 R14: 00000000004d1758 R15: 00000000ffffffff

The buggy address belongs to the page:
page:ffffea0001ecffc0 count:0 mapcount:0 mapping:          (null) index:0x0
flags: 0x1fffc0000000000()
raw: 01fffc0000000000 0000000000000000 0000000000000000 00000000ffffffff
raw: ffffea0001ecffe0 ffffea0001ecffe0 0000000000000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88807b3ffe80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88807b3fff00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88807b3fff80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                                             ^
 ffff88807b400000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88807b400080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================
IPv6: ADDRCONF(NETDEV_UP): veth0_to_team: link is not ready