From: Linus Torvalds <torvalds@linux-foundation.org>
To: Dave Chinner <david@fromorbit.com>
Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>,
LSM List <linux-security-module@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-integrity@vger.kernel.org,
Christoph Hellwig <hch@infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Jan Kara <jack@suse.cz>, "Theodore Ts'o" <tytso@mit.edu>
Subject: Re: [RFC PATCH 3/3] fs: detect that the i_rwsem has already been taken exclusively
Date: Thu, 28 Sep 2017 16:39:23 -0700 [thread overview]
Message-ID: <CA+55aFy-kDL5jQb0q2gHkcmhAwMatEf8YPx8Gh=yGp_VMoVxQA@mail.gmail.com> (raw)
In-Reply-To: <20170928220215.GC15067@dastard>
On Thu, Sep 28, 2017 at 3:02 PM, Dave Chinner <david@fromorbit.com> wrote:
> On Thu, Sep 28, 2017 at 08:39:33AM -0400, Mimi Zohar wrote:
>> Don't attempt to take the i_rwsem, if it has already been taken
>> exclusively.
>>
>> Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
>
> That's bloody awful.
>
> The locking in filesystem IO paths is already complex enough without
> adding a new IO path semantic that says "caller has already locked
> the i_rwsem in some order and some dependencies that we have no idea
> about".
I do have to admit that I never got a satisfactory answer on why IMA
doesn't just use its own private per-inode lock for this all.
It isn't using the i_rwsem for file consistency reasons anyway, so it
seems to be purely about serializing the actual signature generation
with the xattr writing, but since IMA does those both, why isn't IMA
just using its own lock (not the filesystem lock) to do that?
Linus
WARNING: multiple messages have this Message-ID (diff)
From: torvalds@linux-foundation.org (Linus Torvalds)
To: linux-security-module@vger.kernel.org
Subject: [RFC PATCH 3/3] fs: detect that the i_rwsem has already been taken exclusively
Date: Thu, 28 Sep 2017 16:39:23 -0700 [thread overview]
Message-ID: <CA+55aFy-kDL5jQb0q2gHkcmhAwMatEf8YPx8Gh=yGp_VMoVxQA@mail.gmail.com> (raw)
In-Reply-To: <20170928220215.GC15067@dastard>
On Thu, Sep 28, 2017 at 3:02 PM, Dave Chinner <david@fromorbit.com> wrote:
> On Thu, Sep 28, 2017 at 08:39:33AM -0400, Mimi Zohar wrote:
>> Don't attempt to take the i_rwsem, if it has already been taken
>> exclusively.
>>
>> Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
>
> That's bloody awful.
>
> The locking in filesystem IO paths is already complex enough without
> adding a new IO path semantic that says "caller has already locked
> the i_rwsem in some order and some dependencies that we have no idea
> about".
I do have to admit that I never got a satisfactory answer on why IMA
doesn't just use its own private per-inode lock for this all.
It isn't using the i_rwsem for file consistency reasons anyway, so it
seems to be purely about serializing the actual signature generation
with the xattr writing, but since IMA does those both, why isn't IMA
just using its own lock (not the filesystem lock) to do that?
Linus
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next prev parent reply other threads:[~2017-09-28 23:39 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-28 12:39 [RFC PATCH 0/3] define new read_iter file operation rwf flag Mimi Zohar
2017-09-28 12:39 ` Mimi Zohar
2017-09-28 12:39 ` [RFC PATCH 1/3] fs: define new read_iter " Mimi Zohar
2017-09-28 12:39 ` Mimi Zohar
2017-09-28 13:54 ` Matthew Wilcox
2017-09-28 13:54 ` Matthew Wilcox
2017-09-28 14:33 ` Mimi Zohar
2017-09-28 14:33 ` Mimi Zohar
2017-09-28 15:51 ` Linus Torvalds
2017-09-28 15:51 ` Linus Torvalds
2017-09-28 12:39 ` [RFC PATCH 2/3] integrity: use call_read_iter to calculate the file hash Mimi Zohar
2017-09-28 12:39 ` Mimi Zohar
2017-09-28 12:39 ` [RFC PATCH 3/3] fs: detect that the i_rwsem has already been taken exclusively Mimi Zohar
2017-09-28 12:39 ` Mimi Zohar
2017-09-28 22:02 ` Dave Chinner
2017-09-28 22:02 ` Dave Chinner
2017-09-28 23:39 ` Linus Torvalds [this message]
2017-09-28 23:39 ` Linus Torvalds
2017-09-29 0:12 ` Mimi Zohar
2017-09-29 0:12 ` Mimi Zohar
2017-09-29 0:12 ` Mimi Zohar
2017-09-29 0:33 ` Linus Torvalds
2017-09-29 0:33 ` Linus Torvalds
2017-09-29 1:53 ` Mimi Zohar
2017-09-29 1:53 ` Mimi Zohar
2017-09-29 1:53 ` Mimi Zohar
2017-09-29 3:26 ` Linus Torvalds
2017-09-29 3:26 ` Linus Torvalds
2017-10-01 1:33 ` Eric W. Biederman
2017-10-01 1:33 ` Eric W. Biederman
[not found] ` <CA+55aFx726wT4VprN-sHm6s8Q_PV_VjhTBC4goEbMcerYU1Tig@mail.gmail.com>
2017-10-01 12:08 ` Mimi Zohar
2017-10-01 12:08 ` Mimi Zohar
2017-10-01 12:08 ` Mimi Zohar
2017-10-01 18:41 ` Linus Torvalds
2017-10-01 18:41 ` Linus Torvalds
2017-10-01 22:34 ` Dave Chinner
2017-10-01 22:34 ` Dave Chinner
2017-10-01 23:15 ` Linus Torvalds
2017-10-01 23:15 ` Linus Torvalds
2017-10-02 3:54 ` Dave Chinner
2017-10-02 3:54 ` Dave Chinner
2017-10-01 23:42 ` Mimi Zohar
2017-10-01 23:42 ` Mimi Zohar
2017-10-01 23:42 ` Mimi Zohar
2017-10-02 3:25 ` Eric W. Biederman
2017-10-02 3:25 ` Eric W. Biederman
2017-10-02 3:25 ` Eric W. Biederman
2017-10-02 12:25 ` Mimi Zohar
2017-10-02 12:25 ` Mimi Zohar
2017-10-02 12:25 ` Mimi Zohar
2017-10-02 4:35 ` Dave Chinner
2017-10-02 4:35 ` Dave Chinner
2017-10-02 4:35 ` Dave Chinner
2017-10-02 4:35 ` Dave Chinner
2017-10-02 12:09 ` Mimi Zohar
2017-10-02 12:09 ` Mimi Zohar
2017-10-02 12:09 ` Mimi Zohar
2017-10-02 12:43 ` Jeff Layton
2017-10-02 12:43 ` Jeff Layton
2017-10-01 22:06 ` Eric W. Biederman
2017-10-01 22:06 ` Eric W. Biederman
2017-10-01 22:20 ` Linus Torvalds
2017-10-01 22:20 ` Linus Torvalds
2017-10-01 23:54 ` Mimi Zohar
2017-10-01 23:54 ` Mimi Zohar
2017-10-01 23:54 ` Mimi Zohar
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