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BUG: KASAN: use-after-free in erspan_build_header+0x392/0x3b0 net/ipv4/ip_gre.c:706
Read of size 2 at addr ffff8880870b104b by task syz-executor.2/11715

CPU: 1 PID: 11715 Comm: syz-executor.2 Not tainted 4.14.112 #2
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+0x138/0x19c lib/dump_stack.c:53
 print_address_description.cold+0x7c/0x1dc mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report mm/kasan/report.c:409 [inline]
 kasan_report.cold+0xaf/0x2b5 mm/kasan/report.c:393
 __asan_report_load_n_noabort+0xf/0x20 mm/kasan/report.c:440
 erspan_build_header+0x392/0x3b0 net/ipv4/ip_gre.c:706
 erspan_xmit net/ipv4/ip_gre.c:748 [inline]
 erspan_xmit+0x3ec/0x11c0 net/ipv4/ip_gre.c:725
 __netdev_start_xmit include/linux/netdevice.h:4033 [inline]
 netdev_start_xmit include/linux/netdevice.h:4042 [inline]
 packet_direct_xmit+0x438/0x640 net/packet/af_packet.c:269
 packet_snd net/packet/af_packet.c:2969 [inline]
 packet_sendmsg+0x31e1/0x5990 net/packet/af_packet.c:2994
 sock_sendmsg_nosec net/socket.c:646 [inline]
 sock_sendmsg+0xd0/0x110 net/socket.c:656
 ___sys_sendmsg+0x70c/0x850 net/socket.c:2062
 __sys_sendmsg+0xb9/0x140 net/socket.c:2096
 SYSC_sendmsg net/socket.c:2107 [inline]
 SyS_sendmsg+0x2d/0x50 net/socket.c:2103
 do_syscall_64+0x1eb/0x630 arch/x86/entry/common.c:289
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x458c29
RSP: 002b:00007f634218dc78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000458c29
RDX: 0000000000000000 RSI: 0000000020000040 RDI: 0000000000000004
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f634218e6d4
R13: 00000000004c64a3 R14: 00000000004dadd8 R15: 00000000ffffffff

Allocated by task 6952:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x45/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc mm/kasan/kasan.c:551 [inline]
 kasan_kmalloc+0xce/0xf0 mm/kasan/kasan.c:529
 kasan_slab_alloc+0xf/0x20 mm/kasan/kasan.c:489
 kmem_cache_alloc+0x12e/0x780 mm/slab.c:3552
 dup_mmap kernel/fork.c:652 [inline]
 dup_mm kernel/fork.c:1199 [inline]
 copy_mm kernel/fork.c:1253 [inline]
 copy_process.part.0+0x440d/0x6950 kernel/fork.c:1755
 copy_process kernel/fork.c:1570 [inline]
 _do_fork+0x19e/0xce0 kernel/fork.c:2058
 SYSC_clone kernel/fork.c:2168 [inline]
 SyS_clone+0x37/0x50 kernel/fork.c:2162
 do_syscall_64+0x1eb/0x630 arch/x86/entry/common.c:289
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 11696:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x45/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x75/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3496 [inline]
 kmem_cache_free+0x83/0x2b0 mm/slab.c:3758
 remove_vma+0x164/0x1b0 mm/mmap.c:176
 exit_mmap+0x314/0x4e0 mm/mmap.c:3068
 __mmput kernel/fork.c:926 [inline]
 mmput+0x114/0x440 kernel/fork.c:947
 exec_mmap fs/exec.c:1039 [inline]
 flush_old_exec+0x8c0/0x1b50 fs/exec.c:1271
 load_elf_binary+0x88e/0x4ba0 fs/binfmt_elf.c:855
 search_binary_handler fs/exec.c:1638 [inline]
 search_binary_handler+0x14f/0x700 fs/exec.c:1616
 exec_binprm fs/exec.c:1680 [inline]
 do_execveat_common.isra.0+0xffd/0x1dd0 fs/exec.c:1802
 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+0x1eb/0x630 arch/x86/entry/common.c:289
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff8880870b1040
 which belongs to the cache vm_area_struct of size 200
The buggy address is located 11 bytes inside of
 200-byte region [ffff8880870b1040, ffff8880870b1108)
The buggy address belongs to the page:
page:ffffea00021c2c40 count:1 mapcount:0 mapping:ffff8880870b1040 index:0x0
flags: 0x1fffc0000000100(slab)
raw: 01fffc0000000100 ffff8880870b1040 0000000000000000 000000010000000f
raw: ffffea00020eb2e0 ffffea00024c84a0 ffff88821f830c40 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880870b0f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8880870b0f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8880870b1000: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
                                              ^
 ffff8880870b1080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880870b1100: fb fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00
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