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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 ffff8801caa4968b by task syz-executor3/29352

CPU: 0 PID: 29352 Comm: syz-executor3 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
 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: 0033:0x452ef9
RSP: 002b:00007f2b44a3ec58 EFLAGS: 00000212 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452ef9
RDX: 000000000000007e RSI: 000000002000b000 RDI: 0000000000000014
RBP: 00000000000003d6 R08: 0000000020012fe4 R09: 000000000000001c
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f4cb0
R13: 00000000ffffffff R14: 00007f2b44a3f6d4 R15: 0000000000000000

Allocated by task 28583:
 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
 __sigqueue_alloc+0x329/0x660 kernel/signal.c:386
 __send_signal+0x2e8/0x17a0 kernel/signal.c:1041
 send_signal+0x4a/0xc0 kernel/signal.c:1107
 specific_send_sig_info kernel/signal.c:1152 [inline]
 force_sig_info+0x242/0x340 kernel/signal.c:1204
 force_sig_info_fault.constprop.32+0x308/0x460 arch/x86/mm/fault.c:224
 __bad_area_nosemaphore+0x1d2/0x3e0 arch/x86/mm/fault.c:924
 __bad_area arch/x86/mm/fault.c:958 [inline]
 bad_area+0x69/0x80 arch/x86/mm/fault.c:965
 __do_page_fault+0x827/0xc90 arch/x86/mm/fault.c:1400
 do_page_fault+0xee/0x720 arch/x86/mm/fault.c:1505
 page_fault+0x4c/0x60 arch/x86/entry/entry_64.S:1260

Freed by task 28583:
 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
 __sigqueue_free.part.16+0x51/0x60 kernel/signal.c:409
 __sigqueue_free kernel/signal.c:405 [inline]
 collect_signal kernel/signal.c:545 [inline]
 __dequeue_signal+0x46a/0x7b0 kernel/signal.c:566
 dequeue_signal+0xb8/0x550 kernel/signal.c:584
 get_signal+0x385/0x16c0 kernel/signal.c:2228
 do_signal+0x90/0x1eb0 arch/x86/kernel/signal.c:809
 exit_to_usermode_loop+0x214/0x310 arch/x86/entry/common.c:158
 prepare_exit_to_usermode+0x2e1/0x340 arch/x86/entry/common.c:195
 retint_user+0x8/0x18

The buggy address belongs to the object at ffff8801caa49620
 which belongs to the cache sigqueue of size 160
The buggy address is located 107 bytes inside of
 160-byte region [ffff8801caa49620, ffff8801caa496c0)
The buggy address belongs to the page:
page:ffffea00072a9240 count:1 mapcount:0 mapping:ffff8801caa49000 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801caa49000 0000000000000000 0000000100000012
raw: ffffea0007037820 ffffea00070dc460 ffff8801d9ea2ac0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801caa49580: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff8801caa49600: fc fc fc fc fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801caa49680: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
                      ^
 ffff8801caa49700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801caa49780: fb fb fb fb fc fc fc fc fc fc fc fc fb fb fb fb
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