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BUG: KASAN: slab-out-of-bounds in erspan_build_header+0x3bf/0x3d0 net/ipv4/ip_gre.c:698
Read of size 2 at addr ffff8801c70190cb by task syz-executor7/5292

CPU: 0 PID: 5292 Comm: syz-executor7 Not tainted 4.15.0-rc9+ #275
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_build_header+0x3bf/0x3d0 net/ipv4/ip_gre.c:698
 erspan_xmit+0x3b8/0x13b0 net/ipv4/ip_gre.c:740
 __netdev_start_xmit include/linux/netdevice.h:4042 [inline]
 netdev_start_xmit include/linux/netdevice.h:4051 [inline]
 packet_direct_xmit+0x315/0x6b0 net/packet/af_packet.c:266
 packet_snd net/packet/af_packet.c:2943 [inline]
 packet_sendmsg+0x3aed/0x60b0 net/packet/af_packet.c:2968
 sock_sendmsg_nosec net/socket.c:638 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:648
 SYSC_sendto+0x361/0x5c0 net/socket.c:1729
 SyS_sendto+0x40/0x50 net/socket.c:1697
 entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x452ef9
RSP: 002b:00007f0e6325bc58 EFLAGS: 00000212 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 000000000071bf58 RCX: 0000000000452ef9
RDX: 0000000000000000 RSI: 0000000020011000 RDI: 0000000000000013
RBP: 00000000000005e6 R08: 0000000020008000 R09: 000000000000001c
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f7e30
R13: 00000000ffffffff R14: 00007f0e6325c6d4 R15: 0000000000000004

Allocated by task 3693:
 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
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
 kmem_cache_alloc+0x12e/0x760 mm/slab.c:3544
 dup_mmap kernel/fork.c:653 [inline]
 dup_mm kernel/fork.c:1196 [inline]
 copy_mm+0x8d7/0x131b kernel/fork.c:1250
 copy_process.part.38+0x1ee9/0x4b20 kernel/fork.c:1752
 copy_process kernel/fork.c:1565 [inline]
 _do_fork+0x1f7/0xfe0 kernel/fork.c:2044
 SYSC_clone kernel/fork.c:2154 [inline]
 SyS_clone+0x37/0x50 kernel/fork.c:2148
 do_syscall_64+0x273/0x920 arch/x86/entry/common.c:285
 return_from_SYSCALL_64+0x0/0x75

Freed by task 4452:
 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]
 kmem_cache_free+0x83/0x2a0 mm/slab.c:3746
 remove_vma+0x162/0x1b0 mm/mmap.c:176
 exit_mmap+0x311/0x500 mm/mmap.c:3049
 __mmput kernel/fork.c:923 [inline]
 mmput+0x223/0x6d0 kernel/fork.c:944
 exec_mmap fs/exec.c:1039 [inline]
 flush_old_exec+0xc8b/0x2010 fs/exec.c:1271
 load_elf_binary+0x87b/0x4c10 fs/binfmt_elf.c:864
 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 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 ffff8801c7019000
 which belongs to the cache vm_area_struct of size 200
The buggy address is located 3 bytes to the right of
 200-byte region [ffff8801c7019000, ffff8801c70190c8)
The buggy address belongs to the page:
page:ffffea00071c0640 count:1 mapcount:0 mapping:ffff8801c7019000 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801c7019000 0000000000000000 000000010000000f
raw: ffffea00071aa6a0 ffffea00071832a0 ffff8801dae27840 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801c7018f80: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801c7019000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801c7019080: fb fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc
                                              ^
 ffff8801c7019100: fc fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801c7019180: fb fb fb fb fb fb fb fb fb fb fc fc fc fc fc fc
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