Kernel 4.9.51 null pointer dereference add_rule with null key

Fri Aug 17 21:12:06 UTC 2018

On Fri, Aug 17, 2018 at 4:26 PM Preston Bennes
<preston.bennes at snowflake.net> wrote:
> Hey Audit team,

Hey Audit user!

> I've got a kernel null pointer deref oops on Amazon Linux kernel 4.9.51-10.52.amzn1.x86_64. After the oops all new cron processes that spawned were stuck in D wait on some audit related syscall. This exhausted system file handles and the box ended up needing to be rebooted out-of-bounds. The audit handle was held by https://github.com/facebook/osquery/.
>
> It looks like there was an issue with audit sending to osquery (netlink_unicast sending to pid 21233, error -111) followed by something (presumably also osquery) attempting to 'op="add_rule" key=(null)'.

The first thing I need to comment on is that since this is a distro
specific kernel (4.9.51-10.52.amzn1.x86_64) and not an upstream kernel
there is a limit in the amount of help we can provide.  Generally the
upstream list focuses on the upstream code and we leave support for
the distro specific builds/packages up to the distro.  If you can
reproduce your problem on an upstream kernel, with a strong preference
for a *recent* upstream kernel, we can probably be of more help.  I
simply don't know what patches Amazon merges into it's amzn1 kernels.

With that out of the way, I will add that v4.9.x is a rather old
kernel, and we've made a number of relevant improvements since the
v4.9 release and it is unlikely all of them have been backported to
your kernel.  If possible, I would suggest upgrading to a newer kernel
as it may resolve your problem.

There is also a possible issue of osquery as an auditd replacement;
it's unlikely this is being caused by osquery, but we don't test with
osquery to that save level as we do with Steve's audit userspace
(auditd).

> Here's from /var/log/messages.
>
>> Aug 13 14:34:54 packer_default-10-180-21-24 kernel: [4749520.133904] audit: netlink_unicast sending to audit_pid=21233 returned error: -111
>> Aug 13 14:34:54 packer_default-10-180-21-24 kernel: [4749520.137982] audit_log_lost: 12 callbacks suppressed
>> Aug 13 14:34:54 packer_default-10-180-21-24 kernel: [4749520.137983] audit: audit_lost=36081041 audit_rate_limit=8192 audit_backlog_limit=4096
>> Aug 13 14:34:54 packer_default-10-180-21-24 kernel: [4749520.137985] audit: type=1305 audit(1534170894.852:117649229): audit_pid=21233 old=21233 auid=501 ses=102936 res=0
>> Aug 13 14:34:54 packer_default-10-180-21-24 kernel: [4749520.137986] audit: type=1305 audit(1534170894.852:117649230): audit_enabled=1 old=1 auid=501 ses=102936 res=1
>> Aug 13 14:34:54 packer_default-10-180-21-24 kernel: [4749520.137987] audit: type=1305 audit(1534170894.852:117649231): audit_backlog_wait_time=1 old=1 auid=501 ses=102936 res=1
>> Aug 13 14:34:54 packer_default-10-180-21-24 kernel: [4749520.137989] audit: type=1305 audit(1534170894.852:117649232): audit_backlog_limit=4096 old=4096 auid=501 ses=102936 res=1
>> Aug 13 14:34:54 packer_default-10-180-21-24 kernel: [4749520.137990] audit: type=1305 audit(1534170894.852:117649233): audit_failure=0 old=0 auid=501 ses=102936 res=1
>> Aug 13 14:34:54 packer_default-10-180-21-24 kernel: [4749520.137991] audit: type=1305 audit(1534170894.852:117649234): auid=501 ses=102936 op="add_rule" key=(null) list=4 res=0
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.138007] BUG: unable to handle kernel NULL pointer dereference at 00000000000001e0
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.143872] IP: [<ffffffff814a76da>] netlink_unicast+0x4a/0x230
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.148336] PGD 0
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.149822]
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.151230] Oops: 0000 [#1] SMP
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.153736] Modules linked in: iptable_filter(E) ip_tables(E) x_tables(E) udp_diag(E) nfnetlink_queue(E) nfnetlink_log(E) nfnetlink(E) tcp_diag(E) inet_diag(E) isofs(E) ipv6(E) crc_
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.184036] CPU: 0 PID: 21372 Comm: osqueryd Tainted: G            E   4.9.51-10.52.amzn1.x86_64 #1
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.190620] Hardware name: Xen HVM domU, BIOS 4.2.amazon 08/24/2006
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.195513] task: ffff8807fa1c3b00 task.stack: ffffc900079a4000
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.200179] RIP: 0010:[<ffffffff814a76da>]  [<ffffffff814a76da>] netlink_unicast+0x4a/0x230
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.206822] RSP: 0018:ffffc900079a7c38  EFLAGS: 00010246
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.211065] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.216779] RDX: 00001ffffffffffe RSI: 00000000024000c0 RDI: 0000000000000014
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.222473] RBP: ffffc900079a7c68 R08: 0000000000000004 R09: ffff88062a375414
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.228167] R10: ffff8808004032c0 R11: ffff88062a375400 R12: 0000000000000000
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.233738] R13: ffff8804200a0100 R14: 00000000000052f1 R15: 0000000000016d42
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.238999] FS:  00007f3d40cc4700(0000) GS:ffff880800a00000(0000) knlGS:0000000000000000
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.244796] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.249555] CR2: 00000000000001e0 CR3: 000000059e63d000 CR4: 00000000001406f0
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.255401] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.260725] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.266038] Stack:
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.267680]  00000000079a7c58 00000000000052f1 00000000000052f1 00000000ffffffa1
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.273540]  ffff88062a376800 ffff8804200a1d00 ffffc900079a7cf8 ffffffff811107d2
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.279379]  ffffc90000000004 ffffffff811e2f85 ffffc900079a7ca8 ffffffff8145a08c
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.285201] Call Trace:
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.287137]  [<ffffffff811107d2>] audit_receive_msg+0x992/0xc20
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.291561]  [<ffffffff811e2f85>] ? __kmalloc_node_track_caller+0x35/0x260
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.296642]  [<ffffffff8145a08c>] ? release_sock+0x8c/0xa0
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.300718]  [<ffffffff81110ab2>] audit_receive+0x52/0xa0
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.304713]  [<ffffffff814a77ef>] netlink_unicast+0x15f/0x230
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.308943]  [<ffffffff814a7bdc>] netlink_sendmsg+0x31c/0x390
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.313236]  [<ffffffff81455818>] sock_sendmsg+0x38/0x50
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.317219]  [<ffffffff81455c4f>] SYSC_sendto+0xef/0x170
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.321142]  [<ffffffff811156ab>] ? __audit_syscall_entry+0xeb/0x100
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.325853]  [<ffffffff81003437>] ? syscall_trace_enter+0x1b7/0x290
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.330464]  [<ffffffff811158b3>] ? __audit_syscall_exit+0x1f3/0x280
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.335189]  [<ffffffff8145673e>] SyS_sendto+0xe/0x10
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.338952]  [<ffffffff81003854>] do_syscall_64+0x54/0xc0
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.342995]  [<ffffffff8153d32b>] entry_SYSCALL64_slow_path+0x25/0x25
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.347840] Code: 65 8b 05 a2 5b b6 7e 25 00 ff 00 00 83 f8 01 19 f6 81 e6 a0 00 38 00 81 c6 20 00 08 02 e8 af cf ff ff 49 89 c5 31 c0 85 db 75 08 <49> 8b 84 24 e0 01 00 00 48 89 45
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.368625] RIP  [<ffffffff814a76da>] netlink_unicast+0x4a/0x230
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.373253]  RSP <ffffc900079a7c38>
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.376013] CR2: 00000000000001e0
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.379307] ---[ end trace 6a41b2274729ba2a ]---
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.663029] audit: type=1300 audit(1534170895.379:117649235): arch=c000003e syscall=59 success=yes exit=0 a0=271cce0 a1=2741dd0 a2=26dc3b0 a3=7ffdd7f1ea80 items=2 ppid=4556 pid=2407
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.682741] audit: type=1309 audit(1534170895.379:117649235): argc=2 a0="date" a1="+%s"
>> Aug 13 14:34:55 packer_default-10-180-21-24 kernel: [4749520.688585] audit: type=1307 audit(1534170895.379:117649235): cwd="/"
>> Aug 13 14:34:55 packer_default-10-180-21-24 abrt-dump-oops: Reported 1 kernel oopses to Abrt
>
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paul moore
www.paul-moore.com