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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Tue, 14 Jan 2020 16:21:07 +0100
Message-ID: <CACT4Y+bgQVmibpeJgpwb_JTKW6jx3dzv0M-NGVat8qvJTo4X7A@mail.gmail.com>
Subject: Re: inconsistent lock state in ima_process_queued_keys
To:     Mimi Zohar <zohar@linux.ibm.com>
Cc:     syzbot <syzbot+a4a503d7f37292ae1664@syzkaller.appspotmail.com>,
        Lakshmi Ramasubramanian <nramas@linux.microsoft.com>,
        Dmitry Kasatkin <dmitry.kasatkin@gmail.com>,
        James Morris <jmorris@namei.org>,
        linux-integrity@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>,
        linux-security-module <linux-security-module@vger.kernel.org>,
        "Serge E. Hallyn" <serge@hallyn.com>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>
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On Tue, Jan 14, 2020 at 3:57 PM Mimi Zohar <zohar@linux.ibm.com> wrote:
>
> On Tue, 2020-01-14 at 14:58 +0100, Dmitry Vyukov wrote:
> > On Tue, Jan 14, 2020 at 2:56 PM syzbot
> > <syzbot+a4a503d7f37292ae1664@syzkaller.appspotmail.com> wrote:
> > >
> > > Hello,
> > >
> > > syzbot found the following crash on:
> > >
> > > HEAD commit:    1b851f98 Add linux-next specific files for 20200114
> > > git tree:       linux-next
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=12bcbb25e00000
> > > kernel config:  https://syzkaller.appspot.com/x/.config?x=3e7d9cf7ebfa08ad
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=a4a503d7f37292ae1664
> > > 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+a4a503d7f37292ae1664@syzkaller.appspotmail.com
> >
> > +Lakshmi, you seem to have submitted a number of changes to this file recently.
> >
> > This completely breaks linux-next testing for us, every kernel crashes
> > a few minutes after boot.
> >
> > 2020/01/14 14:45:00 vm-26: crash: inconsistent lock state in
> > ima_process_queued_keys
>
> Yikes!  Are you running with an IMA policy?

I don't know.

>  I assume this is being
> caused by commit 8f5d2d06f217 ("IMA: Defined timer to free queued
> keys".  Does reverting it prevent this from happening?

The following seems to help, but don't know if it's the right fix or not.

diff --git a/security/integrity/ima/ima_asymmetric_keys.c
b/security/integrity/ima/ima_asymmetric_keys.c
index 61e478f9e8199..49d559501fe62 100644
--- a/security/integrity/ima/ima_asymmetric_keys.c
+++ b/security/integrity/ima/ima_asymmetric_keys.c
@@ -103,17 +103,18 @@ static bool ima_queue_key(struct key *keyring,
const void *payload,
 {
        bool queued = false;
        struct ima_key_entry *entry;
+       unsigned long flags;

        entry = ima_alloc_key_entry(keyring, payload, payload_len);
        if (!entry)
                return false;

-       spin_lock(&ima_keys_lock);
+       spin_lock_irqsave(&ima_keys_lock, flags);
        if (!ima_process_keys) {
                list_add_tail(&entry->list, &ima_keys);
                queued = true;
        }
-       spin_unlock(&ima_keys_lock);
+       spin_unlock_irqrestore(&ima_keys_lock, flags);

        if (!queued)
                ima_free_key_entry(entry);