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BUG: KASAN: slab-out-of-bounds in __read_once_size include/linux/compiler.h:183 [inline]
BUG: KASAN: slab-out-of-bounds in bpf_fd_array_map_lookup_elem+0x440/0x4c0 kernel/bpf/arraymap.c:374
Read of size 8 at addr ffff8801c0285bb8 by task syz-executor6/7273

CPU: 0 PID: 7273 Comm: syz-executor6 Not tainted 4.15.0-rc7+ #261
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+0x194/0x257 lib/dump_stack.c:53
 print_address_description+0x73/0x250 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report+0x25b/0x340 mm/kasan/report.c:409
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
 __read_once_size include/linux/compiler.h:183 [inline]
 bpf_fd_array_map_lookup_elem+0x440/0x4c0 kernel/bpf/arraymap.c:374
 map_lookup_elem+0x6b5/0xbd0 kernel/bpf/syscall.c:577
 SYSC_bpf kernel/bpf/syscall.c:1711 [inline]
 SyS_bpf+0x922/0x4400 kernel/bpf/syscall.c:1685
 entry_SYSCALL_64_fastpath+0x23/0x9a
RIP: 0033:0x452cf9
RSP: 002b:00007f200dfd2c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452cf9
RDX: 0000000000000018 RSI: 00000000206d1fe8 RDI: 0000000000000001
RBP: 0000000000000037 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006ee5c8
R13: 00000000ffffffff R14: 00007f200dfd36d4 R15: 0000000000000000

Allocated by task 4769:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
 kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3610
 kmalloc include/linux/slab.h:499 [inline]
 kzalloc include/linux/slab.h:688 [inline]
 mca_alloc net/ipv6/mcast.c:838 [inline]
 ipv6_dev_mc_inc+0x3c1/0xb10 net/ipv6/mcast.c:897
 ipv6_add_dev+0xac0/0x12f0 net/ipv6/addrconf.c:471
 addrconf_notify+0x861/0x2270 net/ipv6/addrconf.c:3380
 notifier_call_chain+0x136/0x2c0 kernel/notifier.c:93
 __raw_notifier_call_chain kernel/notifier.c:394 [inline]
 raw_notifier_call_chain+0x2d/0x40 kernel/notifier.c:401
 call_netdevice_notifiers_info+0x32/0x60 net/core/dev.c:1691
 call_netdevice_notifiers net/core/dev.c:1709 [inline]
 register_netdevice+0xd2a/0x1010 net/core/dev.c:7739
 register_netdev+0x1a/0x30 net/core/dev.c:7824
 loopback_net_init+0x76/0x160 drivers/net/loopback.c:214
 ops_init+0x10a/0x570 net/core/net_namespace.c:118
 setup_net+0x313/0x710 net/core/net_namespace.c:295
 copy_net_ns+0x27c/0x580 net/core/net_namespace.c:419
 create_new_namespaces+0x425/0x880 kernel/nsproxy.c:107
 unshare_nsproxy_namespaces+0xae/0x1e0 kernel/nsproxy.c:206
 SYSC_unshare kernel/fork.c:2365 [inline]
 SyS_unshare+0x653/0xfa0 kernel/fork.c:2315
 entry_SYSCALL_64_fastpath+0x23/0x9a

Freed by task 3553:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3488 [inline]
 kfree+0xd6/0x260 mm/slab.c:3803
 free_bprm+0x19d/0x200 fs/exec.c:1414
 do_execveat_common.isra.30+0x1a24/0x23c0 fs/exec.c:1812
 do_execve fs/exec.c:1847 [inline]
 SYSC_execve fs/exec.c:1928 [inline]
 SyS_execve+0x39/0x50 fs/exec.c:1923
 do_syscall_64+0x273/0x920 arch/x86/entry/common.c:285
 return_from_SYSCALL_64+0x0/0x75

The buggy address belongs to the object at ffff8801c0285ac0
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 248 bytes inside of
 256-byte region [ffff8801c0285ac0, ffff8801c0285bc0)
The buggy address belongs to the page:
page:ffffea000700a140 count:1 mapcount:0 mapping:ffff8801c02850c0 index:0xffff8801c0285e80
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801c02850c0 ffff8801c0285e80 000000010000000a
raw: ffffea0007365020 ffffea000737c0a0 ffff8801dac007c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801c0285a80: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
 ffff8801c0285b00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8801c0285b80: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
                                        ^
 ffff8801c0285c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801c0285c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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