bisecting fixing commit since 10d6aa565d0593fe4e152e49ab58f47a2952f902
building syzkaller on 6affd8e838ce8a0c7d72445a7f67fe3bde8bbe04
testing commit 10d6aa565d0593fe4e152e49ab58f47a2952f902 with gcc (GCC) 8.1.0
kernel signature: d1bb1b496e4e7772f5433c489f436185cd5eb762522b3e2dbcc11cdb900752f3
all runs: crashed: KASAN: use-after-free Read in bpf_test_finish
testing current HEAD 4f68020fef1c6cf1b680ffb6481ac41379283ea3
testing commit 4f68020fef1c6cf1b680ffb6481ac41379283ea3 with gcc (GCC) 8.1.0
kernel signature: c2f9c73c8d047e2574a3070542bf3dd9e1b435db40243e6ac74c7baaf8c5ca89
run #0: crashed: KASAN: use-after-free Read in bpf_test_finish
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: kernel BUG at mm/slab.c:LINE!
run #8: crashed: KASAN: use-after-free Read in bpf_test_finish
run #9: crashed: KASAN: use-after-free Read in bpf_test_finish
revisions tested: 2, total time: 23m38.698793476s (build: 16m51.740179709s, test: 5m55.130846501s)
the crash still happens on HEAD
commit msg: Linux 4.14.182
crash: KASAN: use-after-free Read in bpf_test_finish
IPv6: ADDRCONF(NETDEV_UP): team_slave_1: link is not ready
team0: Port device team_slave_1 added
IPv6: ADDRCONF(NETDEV_UP): veth0_to_bond: link is not ready
8021q: adding VLAN 0 to HW filter on device bond0
==================================================================
BUG: KASAN: use-after-free in _copy_to_user+0x84/0xb0 lib/usercopy.c:27
Read of size 924 at addr ffff88807abffff3 by task syz-executor.1/7112
IPv6: ADDRCONF(NETDEV_UP): veth0: link is not ready

CPU: 1 PID: 7112 Comm: syz-executor.1 Not tainted 4.14.182-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
 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
 kasan_check_read+0x11/0x20 mm/kasan/kasan.c:272
IPv6: ADDRCONF(NETDEV_UP): veth1: link is not ready
 _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
IPv6: ADDRCONF(NETDEV_UP): team0: link is not ready
8021q: adding VLAN 0 to HW filter on device team0
IPv6: ADDRCONF(NETDEV_UP): veth0_to_bridge: link is not ready
 bpf_prog_test_run_skb+0x66d/0xbc0 net/bpf/test_run.c:144
IPv6: ADDRCONF(NETDEV_UP): veth1_to_bridge: link is not ready
 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+0x46/0xbb
RIP: 0033:0x459829
RSP: 002b:00007f3c64e7bc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000459829
RDX: 0000000000000028 RSI: 0000000020000140 RDI: 000000000000000a
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
IPv6: ADDRCONF(NETDEV_UP): veth0_to_bond: link is not ready
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f3c64e7c6d4
R13: 00000000004bfb92 R14: 00000000004d1758 R15: 00000000ffffffff

The buggy address belongs to the page:
page:ffffea0001eaffc0 count:0 mapcount:0 mapping:          (null) index:0x0
flags: 0x1fffc0000000000()
raw: 01fffc0000000000 0000000000000000 0000000000000000 00000000ffffffff
raw: ffffea0001eaffe0 ffffea0001eaffe0 0000000000000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88807abffe80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88807abfff00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88807abfff80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                                             ^
 ffff88807ac00000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88807ac00080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================