KASAN: global-out-of-bounds Read in inet_diag_bc_sk

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    4b4976a6 Merge branch 'net-ReST-part-three'
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13e3824c100000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b1494ce3fbc02154
dashboard link: https://syzkaller.appspot.com/bug?extid=3f4c9f04a6740870299e
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+3f4c9f04a6740870299e@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KASAN: global-out-of-bounds in cgroup_id include/linux/cgroup.h:312 [inline]
BUG: KASAN: global-out-of-bounds in inet_diag_bc_sk+0xb6e/0xc70 net/ipv4/inet_diag.c:749
Read of size 8 at addr ffffffff8d22eed0 by task syz-executor.2/16922

CPU: 1 PID: 16922 Comm: syz-executor.2 Not tainted 5.7.0-rc2-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+0x188/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0x5/0x315 mm/kasan/report.c:382
 __kasan_report.cold+0x35/0x4d mm/kasan/report.c:511
 kasan_report+0x33/0x50 mm/kasan/common.c:625
 cgroup_id include/linux/cgroup.h:312 [inline]
 inet_diag_bc_sk+0xb6e/0xc70 net/ipv4/inet_diag.c:749
 inet_diag_dump_icsk+0xbe4/0x1306 net/ipv4/inet_diag.c:1061
 __inet_diag_dump+0x8d/0x240 net/ipv4/inet_diag.c:1113
 netlink_dump+0x50b/0xf50 net/netlink/af_netlink.c:2245
 __netlink_dump_start+0x63f/0x910 net/netlink/af_netlink.c:2353
 netlink_dump_start include/linux/netlink.h:246 [inline]
 inet_diag_handler_cmd+0x263/0x2c0 net/ipv4/inet_diag.c:1278
 __sock_diag_cmd net/core/sock_diag.c:233 [inline]
 sock_diag_rcv_msg+0x2fe/0x3e0 net/core/sock_diag.c:264
 netlink_rcv_skb+0x15a/0x410 net/netlink/af_netlink.c:2469
 sock_diag_rcv+0x26/0x40 net/core/sock_diag.c:275
 netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
 netlink_unicast+0x537/0x740 net/netlink/af_netlink.c:1329
 netlink_sendmsg+0x882/0xe10 net/netlink/af_netlink.c:1918
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:672
 sock_write_iter+0x289/0x3c0 net/socket.c:1004
 call_write_iter include/linux/fs.h:1907 [inline]
 do_iter_readv_writev+0x5a8/0x850 fs/read_write.c:694
 do_iter_write fs/read_write.c:999 [inline]
 do_iter_write+0x18b/0x600 fs/read_write.c:980
 vfs_writev+0x1b3/0x2f0 fs/read_write.c:1072
 do_writev+0x27f/0x300 fs/read_write.c:1115
 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x45c829
Code: 0d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 db b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f6839177c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 000000000050d140 RCX: 000000000045c829
RDX: 0000000000000001 RSI: 00000000200000c0 RDI: 0000000000000007
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000d18 R14: 00000000004cb1f4 R15: 00007f68391786d4

The buggy address belongs to the variable:
 __key.82892+0x30/0x40

Memory state around the buggy address:
 ffffffff8d22ed80: fa fa fa fa 00 00 fa fa fa fa fa fa 00 00 fa fa
 ffffffff8d22ee00: fa fa fa fa 00 fa fa fa fa fa fa fa 00 00 fa fa
>ffffffff8d22ee80: fa fa fa fa 00 00 fa fa fa fa fa fa 00 00 fa fa
                                                 ^
 ffffffff8d22ef00: fa fa fa fa 00 00 fa fa fa fa fa fa 00 00 fa fa
 ffffffff8d22ef80: fa fa fa fa 00 00 fa fa fa fa fa fa 00 00 fa fa
==================================================================


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