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BUG: KASAN: use-after-free in erspan_build_header+0x3bf/0x3d0 net/ipv4/ip_gre.c:698
Read of size 2 at addr ffff8801d60330cb by task syzkaller112255/3659

CPU: 0 PID: 3659 Comm: syzkaller112255 Not tainted 4.15.0-rc9+ #274
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: 0033:0x4454e9
RSP: 002b:00007fffd78af2c8 EFLAGS: 00000217 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: ffffffffffffffff RCX: 00000000004454e9
RDX: 0000000000000000 RSI: 0000000020003fd9 RDI: 0000000000000004
RBP: 00000000004a7093 R08: 0000000020008000 R09: 000000000000001c
R10: 0000000000000001 R11: 0000000000000217 R12: 00007fffd78af378
R13: 00000000004026b0 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 3785:
 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
 getname_flags+0xcb/0x580 fs/namei.c:138
 getname+0x19/0x20 fs/namei.c:209
 SYSC_execve fs/exec.c:1928 [inline]
 SyS_execve+0x1f/0x50 fs/exec.c:1923
 do_syscall_64+0x273/0x920 arch/x86/entry/common.c:285
 return_from_SYSCALL_64+0x0/0x75

Freed by task 3785:
 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
 putname+0xee/0x130 fs/namei.c:258
 do_execveat_common.isra.30+0x1a38/0x23c0 fs/exec.c:1814
 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 ffff8801d6032280
 which belongs to the cache names_cache of size 4096
The buggy address is located 3659 bytes inside of
 4096-byte region [ffff8801d6032280, ffff8801d6033280)
The buggy address belongs to the page:
page:ffffea0007580c80 count:1 mapcount:0 mapping:ffff8801d6032280 index:0x0 compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801d6032280 0000000000000000 0000000100000001
raw: ffffea0007580c20 ffffea0007580da0 ffff8801dae2c600 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d6032f80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d6033000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801d6033080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                              ^
 ffff8801d6033100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d6033180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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