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BUG: KASAN: use-after-free in erspan_xmit+0x22d4/0x2430 net/ipv4/ip_gre.c:735
device syz5 entered promiscuous mode
Read of size 2 at addr ffff8801bca26dcb by task syz-executor0/15548

CPU: 1 PID: 15548 Comm: syz-executor0 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:00007f98646ebc58 EFLAGS: 00000212 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007f98646ec700 RCX: 0000000000452f19
RDX: 0000000000000055 RSI: 0000000020011fab RDI: 0000000000000013
RBP: 0000000000000000 R08: 0000000020009fe4 R09: 000000000000001c
R10: 0000000000000000 R11: 0000000000000212 R12: 0000000000000000
R13: 0000000000a2f7cf R14: 00007f98646ec9c0 R15: 0000000000000000

Allocated by task 13299:
 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
 __split_vma+0x10b/0x7b0 mm/mmap.c:2564
 split_vma+0x8f/0xc0 mm/mmap.c:2627
 mprotect_fixup+0x47a/0x640 mm/mprotect.c:348
 do_mprotect_pkey+0x57d/0x900 mm/mprotect.c:492
 SYSC_mprotect mm/mprotect.c:517 [inline]
 SyS_mprotect+0x2a/0x40 mm/mprotect.c:514
 entry_SYSCALL_64_fastpath+0x29/0xa0

Freed by task 13299:
 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 ffff8801bca26da8
 which belongs to the cache vm_area_struct of size 200
The buggy address is located 35 bytes inside of
 200-byte region [ffff8801bca26da8, ffff8801bca26e70)
The buggy address belongs to the page:
page:ffffea0006f28980 count:1 mapcount:0 mapping:ffff8801bca26040 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801bca26040 0000000000000000 000000010000000f
raw: ffffea0006f4a2a0 ffffea0006f3b0e0 ffff8801dae27840 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801bca26c80: fc fc fc fc fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801bca26d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc
>ffff8801bca26d80: fc fc fc fc fc fb fb fb fb fb fb fb fb fb fb fb
                                              ^
 ffff8801bca26e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
 ffff8801bca26e80: fc fc fc fc fc fc fb fb fb fb fb fb fb fb fb fb
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