WARNING in apparmor_secid_to_secctx

On 09/01/2018 09:33 PM, Dmitry Vyukov wrote:

On Sat, Sep 1, 2018 at 11:18 AM, John Johansen
[off-list ref] wrote:

quoted

On 08/29/2018 07:17 PM, syzbot wrote:

quoted

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

---

From 22dad84baabf4174f11f5e9b34a05529084fa29c Mon Sep 17 00:00:00 2001

From: John Johansen <john.johansen@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@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