linux-kernel - Re: [PATCH 1/3] ima: Remove inode lock

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <9c8979adb9b575d2f938043f61e2be82c898632a.camel@huaweicloud.com>
Date: Wed, 27 Nov 2024 16:57:27 +0100
From: Roberto Sassu <roberto.sassu@...weicloud.com>
To: Shu Han <ebpqwerty472123@...il.com>
Cc: zohar@...ux.ibm.com, dmitry.kasatkin@...il.com,
 eric.snowberg@...cle.com,  paul@...l-moore.com, jmorris@...ei.org,
 serge@...lyn.com,  linux-integrity@...r.kernel.org,
 linux-security-module@...r.kernel.org,  linux-kernel@...r.kernel.org,
 bpf@...r.kernel.org, Roberto Sassu <roberto.sassu@...wei.com>
Subject: Re: [PATCH 1/3] ima: Remove inode lock

On Wed, 2024-10-09 at 23:59 +0800, Shu Han wrote:
> > Finally, expand the critical region in process_measurement()
> > guarded by
> > iint->mutex up to where the inode was locked, use only one iint
> > lock in
> > __ima_inode_hash(), since the mutex is now in the inode security
> > blob, and
> > replace the inode_lock()/inode_unlock() calls in
> > ima_check_last_writer().
> 
> I am not familiar with this, so the following statement may be
> inaccurate:
> 
> I suspect that modifying the `i_flags` field through
> `inode->i_flags |= S_IMA;` in `ima_inode_get` may cause a
> race, as this patch removes the write lock for inodes in
> process_measurement().
> 
> For example, swapon() adds the S_SWAPFILE tag under inode write
> lock's
> protection.
> 
> Perhaps this initialization tag(`S_IMA`) can also be moved into
> inode's
> security blob.

It would not even be necessary, since after making IMA as a regular LSM
the S_IMA check can be replaced by testing whether or not the pointer
of inode integrity metadata in the security blob is NULL.

Will remove S_IMA.

Thanks

Roberto