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BUG: KASAN: use-after-free in erspan_xmit+0x22d4/0x2430 net/ipv4/ip_gre.c:735
Read of size 2 at addr ffff8801d2d1e84b by task syz-executor6/3449

CPU: 1 PID: 3449 Comm: syz-executor6 Not tainted 4.15.0-rc8+ #204
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_load_n_noabort+0xf/0x20 mm/kasan/report.c:440
 erspan_xmit+0x22d4/0x2430 net/ipv4/ip_gre.c:735
 __netdev_start_xmit include/linux/netdevice.h:4055 [inline]
 netdev_start_xmit include/linux/netdevice.h:4064 [inline]
 packet_direct_xmit+0x3ad/0x790 net/packet/af_packet.c:267
 packet_snd net/packet/af_packet.c:2944 [inline]
 packet_sendmsg+0x3aed/0x60b0 net/packet/af_packet.c:2969
sctp: [Deprecated]: syz-executor1 (pid 3476) Use of struct sctp_assoc_value in delayed_ack socket option.
Use struct sctp_sack_info instead
 sock_sendmsg_nosec net/socket.c:630 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:640
 SYSC_sendto+0x361/0x5c0 net/socket.c:1721
 SyS_sendto+0x40/0x50 net/socket.c:1689
 entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x452f19
RSP: 002b:00007f238e61cc58 EFLAGS: 00000212 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452f19
RDX: 0000000000000000 RSI: 0000000020003fd9 RDI: 0000000000000013
RBP: 0000000000000150 R08: 000000002000f000 R09: 000000000000001c
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f1020
R13: 00000000ffffffff R14: 00007f238e61d6d4 R15: 0000000000000000

Allocated by task 32322:
 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
 __do_kmalloc mm/slab.c:3708 [inline]
 __kmalloc+0x162/0x760 mm/slab.c:3717
 kmalloc include/linux/slab.h:504 [inline]
 load_elf_binary+0x706/0x4c10 fs/binfmt_elf.c:757
 search_binary_handler+0x142/0x6b0 fs/exec.c:1638
 exec_binprm fs/exec.c:1680 [inline]
 do_execveat_common.isra.30+0x1754/0x23c0 fs/exec.c:1802
 do_execve+0x31/0x40 fs/exec.c:1847
 call_usermodehelper_exec_async+0x457/0x8f0 kernel/umh.c:100
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:541

Freed by task 32322:
 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
 load_elf_binary+0x24a8/0x4c10 fs/binfmt_elf.c:1096
 search_binary_handler+0x142/0x6b0 fs/exec.c:1638
 exec_binprm fs/exec.c:1680 [inline]
 do_execveat_common.isra.30+0x1754/0x23c0 fs/exec.c:1802
 do_execve+0x31/0x40 fs/exec.c:1847
 call_usermodehelper_exec_async+0x457/0x8f0 kernel/umh.c:100
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:541

The buggy address belongs to the object at ffff8801d2d1e840
 which belongs to the cache kmalloc-32 of size 32
The buggy address is located 11 bytes inside of
 32-byte region [ffff8801d2d1e840, ffff8801d2d1e860)
The buggy address belongs to the page:
page:ffffea00074b4780 count:1 mapcount:0 mapping:ffff8801d2d1e000 index:0xffff8801d2d1efc1
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d2d1e000 ffff8801d2d1efc1 000000010000003f
raw: ffffea00074c2160 ffffea0007554e60 ffff8801dac001c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d2d1e700: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
 ffff8801d2d1e780: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
>ffff8801d2d1e800: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
                                              ^
 ffff8801d2d1e880: fb fb fb fb fc fc fc fc 00 fc fc fc fc fc fc fc
 ffff8801d2d1e900: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
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