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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 ffff8801bc6b258b by task syz-executor7/6455

CPU: 0 PID: 6455 Comm: syz-executor7 Not tainted 4.15.0+ #198
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
 do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline]
 do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
 entry_SYSENTER_compat+0x54/0x63 arch/x86/entry/entry_64_compat.S:129
RIP: 0023:0xf7f49c79
RSP: 002b:00000000f774508c EFLAGS: 00000296 ORIG_RAX: 0000000000000171
RAX: ffffffffffffffda RBX: 0000000000000013 RCX: 0000000020015f41
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020015fec
RBP: 0000000000000014 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 6364:
 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
 __do_kmalloc_node mm/slab.c:3672 [inline]
 __kmalloc_node+0x47/0x70 mm/slab.c:3679
 kmalloc_node include/linux/slab.h:541 [inline]
 kvmalloc_node+0x99/0xd0 mm/util.c:397
 kvmalloc include/linux/mm.h:541 [inline]
 seq_buf_alloc fs/seq_file.c:29 [inline]
 seq_read+0x7cd/0x13d0 fs/seq_file.c:205
 __vfs_read+0xef/0xa00 fs/read_write.c:411
 vfs_read+0x11e/0x350 fs/read_write.c:447
 SYSC_pread64 fs/read_write.c:611 [inline]
 SyS_pread64+0x15b/0x190 fs/read_write.c:598
 sys32_pread+0x39/0x50 arch/x86/ia32/sys_ia32.c:180
 do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline]
 do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
 entry_SYSENTER_compat+0x54/0x63 arch/x86/entry/entry_64_compat.S:129

Freed by task 6364:
 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]
 kfree+0xd6/0x260 mm/slab.c:3803
 kvfree+0x36/0x60 mm/util.c:416
 seq_release fs/seq_file.c:365 [inline]
 single_release+0x78/0xb0 fs/seq_file.c:602
 __fput+0x327/0x7e0 fs/file_table.c:210
 ____fput+0x15/0x20 fs/file_table.c:244
 task_work_run+0x199/0x270 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0x9bb/0x1ad0 kernel/exit.c:865
 do_group_exit+0x149/0x400 kernel/exit.c:968
 get_signal+0x73a/0x16d0 kernel/signal.c:2467
 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 arch/x86/entry/common.c:195 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:264 [inline]
 do_syscall_32_irqs_on arch/x86/entry/common.c:333 [inline]
 do_fast_syscall_32+0xbfd/0xf9d arch/x86/entry/common.c:389
 entry_SYSENTER_compat+0x54/0x63 arch/x86/entry/entry_64_compat.S:129

The buggy address belongs to the object at ffff8801bc6b2a80
 which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 1269 bytes to the left of
 4096-byte region [ffff8801bc6b2a80, ffff8801bc6b3a80)
The buggy address belongs to the page:
page:ffffea0006f1ac80 count:1 mapcount:0 mapping:ffff8801bc6b2a80 index:0x0 compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801bc6b2a80 0000000000000000 0000000100000001
raw: ffffea0006ee38a0 ffffea0006f1afa0 ffff8801db000dc0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801bc6b2480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801bc6b2500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801bc6b2580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                      ^
 ffff8801bc6b2600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801bc6b2680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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