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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 ffff8801bb764ccb by task syz-executor3/5144

CPU: 0 PID: 5144 Comm: syz-executor3 Not tainted 4.15.0-rc9+ #206
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
 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:00007f9925045c58 EFLAGS: 00000212 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452f19
RDX: 0000000000000000 RSI: 0000000020003fd9 RDI: 0000000000000013
RBP: 00000000000003d6 R08: 000000002001cfe4 R09: 000000000000001c
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f4cb0
R13: 00000000ffffffff R14: 00007f99250466d4 R15: 0000000000000000

Allocated by task 5096:
 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
 kmem_cache_zalloc include/linux/slab.h:678 [inline]
 mmap_region+0x7ee/0x15a0 mm/mmap.c:1673
 do_mmap+0x6c0/0xe00 mm/mmap.c:1483
 do_mmap_pgoff include/linux/mm.h:2217 [inline]
 vm_mmap_pgoff+0x1de/0x280 mm/util.c:333
 vm_mmap+0x6a/0x90 mm/util.c:352
 elf_map+0x1c7/0x230 fs/binfmt_elf.c:378
 load_elf_interp fs/binfmt_elf.c:582 [inline]
 load_elf_binary+0x1e0c/0x4c10 fs/binfmt_elf.c:1075
 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 5096:
 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
 exit_mm kernel/exit.c:544 [inline]
 do_exit+0x90a/0x1ad0 kernel/exit.c:852
 do_group_exit+0x149/0x400 kernel/exit.c:968
 SYSC_exit_group kernel/exit.c:979 [inline]
 SyS_exit_group+0x1d/0x20 kernel/exit.c:977
 entry_SYSCALL_64_fastpath+0x29/0xa0

The buggy address belongs to the object at ffff8801bb764c60
 which belongs to the cache vm_area_struct of size 200
The buggy address is located 107 bytes inside of
 200-byte region [ffff8801bb764c60, ffff8801bb764d28)
The buggy address belongs to the page:
page:ffffea0006edd900 count:1 mapcount:0 mapping:ffff8801bb764000 index:0xffff8801bb764b58
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801bb764000 ffff8801bb764b58 000000010000000e
raw: ffffea00073350e0 ffffea0007194920 ffff8801dae27840 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801bb764b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801bb764c00: fb fb fb fb fc fc fc fc fc fc fc fc fb fb fb fb
>ffff8801bb764c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                              ^
 ffff8801bb764d00: fb fb fb fb fb fc fc fc fc fc fc fc fc fb fb fb
 ffff8801bb764d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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