BUG: unable to handle kernel NULL pointer dereference in fdb_find_rcu

[Andrei Vagin]

Hi,

We run criu tests for linux-next and today we get this bug:

The kernel version is 4.15.0-rc3-next-20171215

[  235.397328] BUG: unable to handle kernel NULL pointer dereference
at 000000000000000c
[  235.398624] IP: fdb_find_rcu+0x3c/0x130
[  235.399365] PGD 51970067 P4D 51970067 PUD 51971067 PMD 0
[  235.400400] Oops: 0000 [#1] SMP
[  235.400959] Modules linked in:
[  235.401455] CPU: 1 PID: 32057 Comm: criu Not tainted
4.15.0-rc3-next-20171215-00002-g2e56147d7dc8 #10
[  235.402935] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS 1.10.2-1.fc26 04/01/2014
[  235.404356] RIP: 0010:fdb_find_rcu+0x3c/0x130
[  235.405069] RSP: 0018:ffffbc64c05f76e8 EFLAGS: 00010246
[  235.405908] RAX: 000000000000e871 RBX: 0000000000000000 RCX: 0000000000000000
[  235.407062] RDX: 0000000000000000 RSI: ffff9d9b69a04798 RDI: ffff9d9b64c14948
[  235.408370] RBP: ffff9d9b64c14948 R08: ffffbc64c05f7c18 R09: ffff9d9b64c140a0
[  235.409518] R10: 0000000064c140a0 R11: ffff9d9b75743968 R12: ffff9d9b757ce260
[  235.410674] R13: 0000000000000000 R14: ffffbc64c05f7c18 R15: ffffffffa5384560
[  235.411837] FS:  00007ffac2660100(0000) GS:ffff9d9b7fd00000(0000)
knlGS:0000000000000000
[  235.412920] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  235.413764] CR2: 000000000000000c CR3: 000000006a7ff004 CR4: 00000000003606e0
[  235.414829] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  235.416096] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  235.417365] Call Trace:
[  235.417774]  br_fdb_change_mac_address+0x31/0x80
[  235.418538]  br_stp_change_bridge_id+0x25/0x110
[  235.419280]  br_dev_newlink+0x43/0xa0
[  235.419796]  rtnl_newlink+0x70f/0x940
[  235.420391]  ? nla_parse+0x83/0xf0
[  235.420948]  ? nla_strlcpy+0x48/0x50
[  235.421540]  ? rtnl_link_ops_get+0x34/0x50
[  235.422211]  ? rtnl_newlink+0x193/0x940
[  235.422843]  ? deactivate_slab.isra.78+0x11b/0x3b0
[  235.423599]  rtnetlink_rcv_msg+0x25d/0x2d0
[  235.424189]  ? __alloc_skb+0x82/0x1e0
[  235.424718]  ? __slab_alloc+0x1c/0x30
[  235.425420]  ? rtnl_calcit.isra.27+0x110/0x110
[  235.426354]  netlink_rcv_skb+0x8d/0x130
[  235.426995]  netlink_unicast+0x19d/0x250
[  235.427754]  netlink_sendmsg+0x2a5/0x3a0
[  235.428387]  sock_sendmsg+0x30/0x40
[  235.428807]  ___sys_sendmsg+0x269/0x2c0
[  235.429277]  ? generic_perform_write+0x122/0x1b0
[  235.429828]  ? __generic_file_write_iter+0x192/0x1c0
[  235.430422]  ? ext4_file_write_iter+0x20c/0x3e0
[  235.430975]  ? SyS_setns+0xc2/0xd0
[  235.431425]  ? __vfs_write+0xf9/0x170
[  235.431886]  ? __sys_sendmsg+0x51/0x90
[  235.432501]  __sys_sendmsg+0x51/0x90
[  235.433098]  entry_SYSCALL_64_fastpath+0x1a/0x7d
[  235.433822] RIP: 0033:0x7ffac1e170f7
[  235.434409] RSP: 002b:00007ffc5610c688 EFLAGS: 00000246 ORIG_RAX:
000000000000002e
[  235.435635] RAX: ffffffffffffffda RBX: 00000000022eb010 RCX: 00007ffac1e170f7
[  235.436796] RDX: 0000000000000000 RSI: 00007ffc5610c6c0 RDI: 0000000000000002
[  235.437956] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
[  235.439125] R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffc5610cbac
[  235.440556] R13: 0005005800000011 R14: 00007ffac2666158 R15: 0000000000000001
[  235.442175] Code: fd 48 83 ec 10 65 48 8b 04 25 28 00 00 00 48 89
44 24 08 31 c0 8b 06 48 8b 1f 66 89 54 24 06 89 04 24 0f b7 46 04 66
89 44 24 04 <8b> 43 0c 8b 14 24 8d b0 f7 be ad de 8b 44 24 04 01 f2 01
f0 89
[  235.444717] RIP: fdb_find_rcu+0x3c/0x130 RSP: ffffbc64c05f76e8
[  235.445636] CR2: 000000000000000c
[  235.446278] ---[ end trace b77358b1e42a9dd7 ]---
[  235.447170] Kernel panic - not syncing: Fatal exception in interrupt
[  235.448379] Kernel Offset: 0x23000000 from 0xffffffff81000000
(relocation range: 0xffffffff80000000-0xffffffffbfffffff)
[  235.449750] ---[ end Kernel panic - not syncing: Fatal exception in interrupt