KASAN: slab-out-of-bounds Read in __xfrm6_tunnel_spi_check

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    4c43049f Add linux-next specific files for 20200716
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12e58d7d100000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2c76d72659687242
dashboard link: https://syzkaller.appspot.com/bug?extid=7da3fdf292816554b942
compiler:       gcc (GCC) 10.1.0-syz 20200507

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7da3fdf292816554b942@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KASAN: slab-out-of-bounds in __xfrm6_tunnel_spi_check+0x316/0x330 net/ipv6/xfrm6_tunnel.c:108
Read of size 8 at addr ffff8880a93a5e08 by task syz-executor.1/8482
CPU: 0 PID: 8482 Comm: syz-executor.1 Not tainted 5.8.0-rc5-next-20200716-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x18f/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
 __xfrm6_tunnel_spi_check+0x316/0x330 net/ipv6/xfrm6_tunnel.c:108
 __xfrm6_tunnel_alloc_spi net/ipv6/xfrm6_tunnel.c:131 [inline]
 xfrm6_tunnel_alloc_spi+0x296/0x8a0 net/ipv6/xfrm6_tunnel.c:174
 ipcomp6_tunnel_create net/ipv6/ipcomp6.c:84 [inline]
 ipcomp6_tunnel_attach net/ipv6/ipcomp6.c:124 [inline]
 ipcomp6_init_state net/ipv6/ipcomp6.c:159 [inline]
 ipcomp6_init_state+0x2af/0x700 net/ipv6/ipcomp6.c:139
 __xfrm_init_state+0x9a6/0x14b0 net/xfrm/xfrm_state.c:2498
 xfrm_init_state+0x1a/0x70 net/xfrm/xfrm_state.c:2525
 pfkey_msg2xfrm_state net/key/af_key.c:1291 [inline]
 pfkey_add+0x1a10/0x2b70 net/key/af_key.c:1508
 pfkey_process+0x66d/0x7a0 net/key/af_key.c:2834
 pfkey_sendmsg+0x42d/0x800 net/key/af_key.c:3673
 sock_sendmsg_nosec net/socket.c:651 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:671
 ____sys_sendmsg+0x331/0x810 net/socket.c:2362
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2416
 __sys_sendmmsg+0x195/0x480 net/socket.c:2506
 __do_sys_sendmmsg net/socket.c:2535 [inline]
 __se_sys_sendmmsg net/socket.c:2532 [inline]
 __x64_sys_sendmmsg+0x99/0x100 net/socket.c:2532
 do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45c1d9
Code: Bad RIP value.
RSP: 002b:00007fe3fa739c78 EFLAGS: 00000246
 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 0000000000025a40 RCX: 000000000045c1d9
RDX: 0400000000000282 RSI: 0000000020000180 RDI: 0000000000000003
RBP: 000000000078bf48 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000078bf0c
R13: 00007fffec91896f R14: 00007fe3fa73a9c0 R15: 000000000078bf0c
Allocated by task 1:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461
 kmem_cache_alloc_trace+0x16e/0x2c0 mm/slab.c:3550
 kmalloc include/linux/slab.h:554 [inline]
 kzalloc include/linux/slab.h:666 [inline]
 device_private_init drivers/base/core.c:2763 [inline]
 device_add+0x1008/0x1c40 drivers/base/core.c:2813
 netdev_register_kobject+0x17d/0x3b0 net/core/net-sysfs.c:1888
 register_netdevice+0xd29/0x1540 net/core/dev.c:9523
 register_netdev+0x2d/0x50 net/core/dev.c:9654
 ip6gre_init_net+0x3c4/0x5e0 net/ipv6/ip6_gre.c:1587
 ops_init+0xaf/0x470 net/core/net_namespace.c:151
 __register_pernet_operations net/core/net_namespace.c:1140 [inline]
 register_pernet_operations+0x35a/0x850 net/core/net_namespace.c:1217
 register_pernet_device+0x26/0x70 net/core/net_namespace.c:1304
 ip6gre_init+0x1f/0x132 net/ipv6/ip6_gre.c:2327
 do_one_initcall+0x10a/0x7b0 init/main.c:1201
 do_initcall_level init/main.c:1274 [inline]
 do_initcalls init/main.c:1290 [inline]
 do_basic_setup init/main.c:1310 [inline]
 kernel_init_freeable+0x4f4/0x5a3 init/main.c:1507
 kernel_init+0xd/0x1c0 init/main.c:1401
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
The buggy address belongs to the object at ffff8880a93a5c00
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 8 bytes to the right of
 512-byte region [ffff8880a93a5c00, ffff8880a93a5e00)
The buggy address belongs to the page:
page:0000000064ff38cf refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0xa93a5
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea00028deec8 ffffea00027a5388 ffff8880aa000600
raw: 0000000000000000 ffff8880a93a5000 0000000100000004 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
 ffff8880a93a5d00: 00 fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880a93a5d80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880a93a5e00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                      ^
 ffff8880a93a5e80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880a93a5f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


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