From: zohar@linux.vnet.ibm.com (Mimi Zohar)
To: linux-security-module@vger.kernel.org
Subject: [PATCH 3/3] ima: use fs method to read integrity data
Date: Fri, 15 Sep 2017 11:21:21 -0400 [thread overview]
Message-ID: <1505488881.4200.96.camel@linux.vnet.ibm.com> (raw)
In-Reply-To: <20170915144903.GA3854@infradead.org>
On Fri, 2017-09-15 at 07:49 -0700, Christoph Hellwig wrote:
> On Thu, Sep 14, 2017 at 10:50:27PM -0700, Linus Torvalds wrote:
> > This is still wrong.
> >
> > (a) there is no explanation for why we need that exclusive lock in the
> > first place
> >
> > Why should a read need exclusive access? You'd think shared is sufficient.
> > But regardless, it needs *explanation*.
>
> Shared is sufficient, and nothing in the patch (except for the
> description) actually requires an exclusive lock. It just happens that
> ima holds it exclusive for other internal reasons.
Although reading the file to calculate the file hash doesn't require
taking the lock exclusively, in either "fix" mode or called from
__fput, immediately after calculating the file hash, the file hash is
written out as an xattr. ?Writing the xattr requires taking the lock
exclusively.
Mimi
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WARNING: multiple messages have this Message-ID (diff)
From: Mimi Zohar <zohar@linux.vnet.ibm.com>
To: Christoph Hellwig <hch@infradead.org>,
Linus Torvalds <torvalds@linux-foundation.org>
Cc: Dave Kleikamp <shaggy@kernel.org>,
Bob Peterson <rpeterso@redhat.com>,
David Woodhouse <dwmw2@infradead.org>,
Chao Yu <yuchao0@huawei.com>, Hugh Dickins <hughd@google.com>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
Matthew Garrett <mjg59@srcf.ucam.org>,
Joel Becker <jlbec@evilplan.org>, Jan Kara <jack@suse.com>,
Chris Mason <clm@fb.com>,
Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>,
Steven Whitehouse <swhiteho@redhat.com>,
Andreas Dilger <adilger.kernel@dilger.ca>,
"Theodore Ts'o" <tytso@mit.edu>,
Mark Fasheh <mfasheh@versity.com>,
linux-security-module@vger.kernel.org,
linux-ima-devel@lists.sourceforge.net,
James Morris <jmorris@namei.org>,
Richard Weinberger <richard@nod.at>,
Jaegeuk Kim <jaegeuk@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 3/3] ima: use fs method to read integrity data
Date: Fri, 15 Sep 2017 11:21:21 -0400 [thread overview]
Message-ID: <1505488881.4200.96.camel@linux.vnet.ibm.com> (raw)
In-Reply-To: <20170915144903.GA3854@infradead.org>
On Fri, 2017-09-15 at 07:49 -0700, Christoph Hellwig wrote:
> On Thu, Sep 14, 2017 at 10:50:27PM -0700, Linus Torvalds wrote:
> > This is still wrong.
> >
> > (a) there is no explanation for why we need that exclusive lock in the
> > first place
> >
> > Why should a read need exclusive access? You'd think shared is sufficient.
> > But regardless, it needs *explanation*.
>
> Shared is sufficient, and nothing in the patch (except for the
> description) actually requires an exclusive lock. It just happens that
> ima holds it exclusive for other internal reasons.
Although reading the file to calculate the file hash doesn't require
taking the lock exclusively, in either "fix" mode or called from
__fput, immediately after calculating the file hash, the file hash is
written out as an xattr. Writing the xattr requires taking the lock
exclusively.
Mimi
next prev parent reply other threads:[~2017-09-15 15:21 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-15 4:58 [PATCH 0/3] ima: only call integrity_kernel_read to calc file hash Mimi Zohar
2017-09-15 4:58 ` Mimi Zohar
2017-09-15 4:58 ` [PATCH 1/3] vfs: constify path argument to kernel_read_file_from_path Mimi Zohar
2017-09-15 4:58 ` Mimi Zohar
2017-09-15 18:37 ` Linus Torvalds
2017-09-15 18:37 ` Linus Torvalds
2017-09-15 4:58 ` [PATCH 2/3] integrity: replace call to integrity_read_file with kernel version Mimi Zohar
2017-09-15 4:58 ` Mimi Zohar
2017-09-15 4:58 ` [PATCH 3/3] ima: use fs method to read integrity data Mimi Zohar
2017-09-15 4:58 ` Mimi Zohar
[not found] ` <CA+55aFwVujvsdaq09O216u-uBbBbo5i_1d6aw3ksottR_uiJ6w@mail.gmail.com>
2017-09-15 9:04 ` Mimi Zohar
2017-09-15 9:04 ` Mimi Zohar
2017-09-15 9:09 ` Mimi Zohar
2017-09-15 9:09 ` Mimi Zohar
2017-09-15 18:05 ` Linus Torvalds
2017-09-15 18:05 ` Linus Torvalds
2017-09-15 14:49 ` Christoph Hellwig
2017-09-15 14:49 ` Christoph Hellwig
2017-09-15 15:21 ` Mimi Zohar [this message]
2017-09-15 15:21 ` Mimi Zohar
2017-09-15 20:25 ` [PATCH 3/3] ima: use fs method to read integrity data (updated patch description) Mimi Zohar
2017-09-15 20:25 ` Mimi Zohar
2017-09-16 18:20 ` Linus Torvalds
2017-09-16 18:20 ` Linus Torvalds
2017-09-17 5:47 ` Mimi Zohar
2017-09-17 5:47 ` Mimi Zohar
2017-09-17 15:17 ` Christoph Hellwig
2017-09-17 15:17 ` Christoph Hellwig
2017-09-17 15:28 ` Linus Torvalds
2017-09-17 15:28 ` Linus Torvalds
2017-09-17 15:37 ` Christoph Hellwig
2017-09-17 15:37 ` Christoph Hellwig
2017-09-17 16:15 ` Mimi Zohar
2017-09-17 16:15 ` Mimi Zohar
2017-09-17 16:34 ` Linus Torvalds
2017-09-17 16:34 ` Linus Torvalds
2017-09-17 16:38 ` Al Viro
2017-09-17 16:38 ` Al Viro
2017-09-18 9:19 ` Steven Whitehouse
2017-09-18 9:19 ` Steven Whitehouse
2017-09-18 10:13 ` Jan Kara
2017-09-18 10:13 ` Jan Kara
2017-09-18 14:55 ` Mimi Zohar
2017-09-18 14:55 ` Mimi Zohar
2017-09-24 22:55 ` Mimi Zohar
2017-09-24 22:55 ` Mimi Zohar
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