linux-kernel - Re: [syzbot] [integrity?] [lsm?] possible deadlock in process

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Message-ID: <CAHQche-HPzahcHea65f-caRBUSvr4WsRF5J8cqYGnjJvBNTX5g@mail.gmail.com>
Date: Thu, 3 Oct 2024 15:35:51 +0800
From: Shu Han <ebpqwerty472123@...il.com>
To: Paul Moore <paul@...l-moore.com>
Cc: syzbot <syzbot+1cd571a672400ef3a930@...kaller.appspotmail.com>, 
	akpm@...ux-foundation.org, dmitry.kasatkin@...il.com, 
	eric.snowberg@...cle.com, hughd@...gle.com, jmorris@...ei.org, 
	linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-mm@...ck.org, linux-security-module@...r.kernel.org, 
	roberto.sassu@...wei.com, serge@...lyn.com, stephen.smalley.work@...il.com, 
	syzkaller-bugs@...glegroups.com, zohar@...ux.ibm.com
Subject: Re: [syzbot] [integrity?] [lsm?] possible deadlock in
 process_measurement (4)

> My apologies for the delay on this, I was traveling for a bit and
> missed this issue while away.
>
> Looking quickly at the report, I don't believe this is a false positive.

This is the mistake I made when I first watched the report.

It should be a deadlock.

> Looking at the IMA code, specifically the process_measurement()
> function which is called from the security_mmap_file() LSM hook, I'm
> not sure why there is the inode_lock() protected region.  Mimi?
> Roberto?  My best guess is that locking the inode may have been
> necessary before we moved the IMA inode state into the inode's LSM
> security blob, but I'm not certain.
>
> Mimi and Roberto, can we safely remove the inode locking in
> process_measurement()?

It would be better if IMA could avoid acqurie inode_lock().

If not, then we may need to consider solutions I mentioned in my
previous reply.