WARNING in apparmor_secid_to_secctx

Sun Sep 2 05:03:54 UTC 2018

> On Sun, Sep 2, 2018 at 6:52 AM, John Johansen
> <john.johansen at canonical.com> wrote:
>> On 09/01/2018 09:33 PM, Dmitry Vyukov wrote:
>>> On Sat, Sep 1, 2018 at 11:18 AM, John Johansen
>>> <john.johansen at canonical.com> wrote:
>>>> On 08/29/2018 07:17 PM, syzbot wrote:
>>>>> Hello,

>>>>> syzbot found the following crash on:

>>>>> HEAD commit:    817e60a7a2bb Merge branch 'nfp-add-NFP5000-support'
>>>>> git tree:       net-next
>>>>> console output:  
>>>>> https://syzkaller.appspot.com/x/log.txt?x=1536d296400000
>>>>> kernel config:   
>>>>> https://syzkaller.appspot.com/x/.config?x=531a917630d2a492
>>>>> dashboard link:  
>>>>> https://syzkaller.appspot.com/bug?extid=21016130b0580a9de3b5
>>>>> compiler:       gcc (GCC) 8.0.1 20180413 (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+21016130b0580a9de3b5 at syzkaller.appspotmail.com

>>>> << snip >>

>>>> Patch sent directly to syzbot for testing

>>> Hi John,

>>> What do you mean? syzbot has not received any test requests for this,
>>> and it would reply within half an hour or so. Where is that patch?

>> Hrmmm strange I followed the web instruction and attached the patch to  
>> the
>> reply. The patch is below, its also available at

>> git://git.kernel.org/pub/scm/linux/kernel/git/jj/linux-apparmor  
>> 4.18-syzbot-secid

> Humm.. Maybe you did not send it to syzbot?  The command should be just:

> #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/jj/linux-apparmor

"git://git.kernel.org/pub/scm/linux/kernel/git/jj/linux-apparmor" does not  
look like a valid git repo address.

> 4.18-syzbot-secid

>> ---

>>  From 22dad84baabf4174f11f5e9b34a05529084fa29c Mon Sep 17 00:00:00 2001
>> From: John Johansen <john.johansen at canonical.com>
>> Date: Sat, 1 Sep 2018 01:57:52 -0700
>> Subject: [PATCH] apparmor: fix apparmor_secid_to_secctx incorrect debug
>>   triggering  WARN_ON

>> apparmor_secid_to_secctx() has a bad debug statement tripping on a
>> condition handle by the code.  When kconfig SECURITY_APPARMOR_DEBUG is
>> enabled the debug WARN_ON will trip when **secdata is NULL resulting
>> in the following trace.

>> ------------[ cut here ]------------
>> AppArmor WARN apparmor_secid_to_secctx: ((!secdata)):
>> WARNING: CPU: 0 PID: 14826 at security/apparmor/secid.c:82  
>> apparmor_secid_to_secctx+0x2b5/0x2f0 security/apparmor/secid.c:82
>> Kernel panic - not syncing: panic_on_warn set ...

>> CPU: 0 PID: 14826 Comm: syz-executor1 Not tainted 4.19.0-rc1+ #193
>> 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+0x1c9/0x2b4 lib/dump_stack.c:113
>>   panic+0x238/0x4e7 kernel/panic.c:184
>>   __warn.cold.8+0x163/0x1ba kernel/panic.c:536
>>   report_bug+0x252/0x2d0 lib/bug.c:186
>>   fixup_bug arch/x86/kernel/traps.c:178 [inline]
>>   do_error_trap+0x1fc/0x4d0 arch/x86/kernel/traps.c:296
>>   do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316
>>   invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:993
>> RIP: 0010:apparmor_secid_to_secctx+0x2b5/0x2f0  
>> security/apparmor/secid.c:82
>> Code: c7 c7 40 66 58 87 e8 6a 6d 0f fe 0f 0b e9 6c fe ff ff e8 3e aa 44  
>> fe 48 c7 c6 80 67 58 87 48 c7 c7 a0 65 58 87 e8 4b 6d 0f fe <0f> 0b e9  
>> 3f fe ff ff 48 89 df e8 fc a7 83 fe e9 ed fe ff ff bb f4
>> RSP: 0018:ffff8801ba1bed10 EFLAGS: 00010286
>> RAX: 0000000000000000 RBX: ffff8801ba1beed0 RCX: ffffc9000227e000
>> RDX: 0000000000018482 RSI: ffffffff8163ac01 RDI: 0000000000000001
>> RBP: ffff8801ba1bed30 R08: ffff8801b80ec080 R09: ffffed003b603eca
>> R10: ffffed003b603eca R11: ffff8801db01f657 R12: 0000000000000001
>> R13: 0000000000000000 R14: 0000000000000000 R15: ffff8801ba1beed0
>>   security_secid_to_secctx+0x63/0xc0 security/security.c:1314
>>   ctnetlink_secctx_size net/netfilter/nf_conntrack_netlink.c:621 [inline]
>>   ctnetlink_nlmsg_size net/netfilter/nf_conntrack_netlink.c:659 [inline]
>>   ctnetlink_conntrack_event+0x303/0x1470  
>> net/netfilter/nf_conntrack_netlink.c:706
>>   nf_conntrack_eventmask_report+0x55f/0x930  
>> net/netfilter/nf_conntrack_ecache.c:151
>>   nf_conntrack_event_report  
>> include/net/netfilter/nf_conntrack_ecache.h:112 [inline]
>>   nf_ct_delete+0x33c/0x5d0 net/netfilter/nf_conntrack_core.c:601
>>   nf_ct_iterate_cleanup+0x48c/0x5e0 net/netfilter/nf_conntrack_core.c:1892
>>   nf_ct_iterate_cleanup_net+0x23c/0x2d0  
>> net/netfilter/nf_conntrack_core.c:1974
>>   ctnetlink_flush_conntrack net/netfilter/nf_conntrack_netlink.c:1226  
>> [inline]
>>   ctnetlink_del_conntrack+0x66c/0x850  
>> net/netfilter/nf_conntrack_netlink.c:1258
>>   nfnetlink_rcv_msg+0xd88/0x1070 net/netfilter/nfnetlink.c:228
>>   netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2454
>>   nfnetlink_rcv+0x1c0/0x4d0 net/netfilter/nfnetlink.c:560
>>   netlink_unicast_kernel net/netlink/af_netlink.c:1317 [inline]
>>   netlink_unicast+0x5a0/0x760 net/netlink/af_netlink.c:1343
>>   netlink_sendmsg+0xa18/0xfc0 net/netlink/af_netlink.c:1908
>>   sock_sendmsg_nosec net/socket.c:621 [inline]
>>   sock_sendmsg+0xd5/0x120 net/socket.c:631
>>   ___sys_sendmsg+0x7fd/0x930 net/socket.c:2114
>>   __sys_sendmsg+0x11d/0x290 net/socket.c:2152
>>   __do_sys_sendmsg net/socket.c:2161 [inline]
>>   __se_sys_sendmsg net/socket.c:2159 [inline]
>>   __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2159
>>   do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
>> RIP: 0033:0x457089
>> Code: fd b4 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 cb b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00
>> RSP: 002b:00007f7bc6e03c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
>> RAX: ffffffffffffffda RBX: 00007f7bc6e046d4 RCX: 0000000000457089
>> RDX: 0000000000000000 RSI: 0000000020d65000 RDI: 0000000000000003
>> RBP: 00000000009300a0 R08: 0000000000000000 R09: 0000000000000000
>> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
>> R13: 00000000004d4588 R14: 00000000004c8d5c R15: 0000000000000000
>> Dumping ftrace buffer:
>>     (ftrace buffer empty)
>> Kernel Offset: disabled
>> Rebooting in 86400 seconds..

>> Fixes: c092921219d2 ("apparmor: add support for mapping secids and using  
>> secctxes")
>> Reported-by: syzbot+21016130b0580a9de3b5 at syzkaller.appspotmail.com
>> Signed-off-by: John Johansen <john.johansen at canonical.com>
>> ---
>>   security/apparmor/secid.c | 1 -
>>   1 file changed, 1 deletion(-)

>> diff --git a/security/apparmor/secid.c b/security/apparmor/secid.c
>> index f2f22d00db18..4ccec1bcf6f5 100644
>> --- a/security/apparmor/secid.c
>> +++ b/security/apparmor/secid.c
>> @@ -79,7 +79,6 @@ int apparmor_secid_to_secctx(u32 secid, char  
>> **secdata, u32 *seclen)
>>          struct aa_label *label = aa_secid_to_label(secid);
>>          int len;

>> -       AA_BUG(!secdata);
>>          AA_BUG(!seclen);

>>          if (!label)
>> --
>> 2.17.1

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