From: "Luck, Tony" <tony.luck@intel.com>
To: Matthew Garrett <mjg59@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
"joe.konno@linux.intel.com" <joe.konno@linux.intel.com>,
linux-efi <linux-efi@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Jeremy Kerr <jk@ozlabs.org>,
"ak@linux.intel.com" <ak@linux.intel.com>,
"pjones@redhat.com" <pjones@redhat.com>,
"luto@kernel.org" <luto@kernel.org>,
James Bottomley <james.bottomley@hansenpartnership.com>
Subject: RE: [PATCH 1/2] fs/efivarfs: restrict inode permissions
Date: Tue, 20 Feb 2018 23:50:08 +0000 [thread overview]
Message-ID: <3908561D78D1C84285E8C5FCA982C28F7B37DB0F@ORSMSX110.amr.corp.intel.com> (raw)
In-Reply-To: <CACdnJussCnLqdGGyOc=iUwEdot_U2DZjGcVWRcQa-DxVcUhabA@mail.gmail.com>
> read() will make two calls - one to obtain the size of the variable, the
> other to read it. It looks like cat will also trigger an fstat(), so we're
> probably also making a call for that. There's presumably some optimisation
> that could be made there if we trust the firmware not to change the size
> behind our back.
Hmmm. "ls -l" reports the size of each of the files without causing any SMIs,
so Linux has that cached someplace and "read" is being silly making a call
to get something that we already know. Unless we think the size may be
changing asynchronously and are OK with reporting a stale value for "stat"
but want the actual value for "read".
-Tony
next prev parent reply other threads:[~2018-02-20 23:50 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-15 18:22 [PATCH 0/2] efivars: reading variables can generate SMIs Joe Konno
2018-02-15 18:22 ` [PATCH 1/2] fs/efivarfs: restrict inode permissions Joe Konno
2018-02-20 19:18 ` Andy Lutomirski
2018-02-20 21:18 ` Luck, Tony
2018-02-20 21:22 ` Matthew Garrett
2018-02-20 21:32 ` Luck, Tony
2018-02-20 21:35 ` Matthew Garrett
2018-02-20 22:01 ` Linus Torvalds
2018-02-20 23:30 ` Luck, Tony
2018-02-20 23:39 ` Matthew Garrett
2018-02-20 23:50 ` Luck, Tony [this message]
2018-02-21 0:49 ` Linus Torvalds
2018-02-21 1:05 ` Luck, Tony
2018-02-21 2:16 ` Linus Torvalds
2018-02-21 9:03 ` Ard Biesheuvel
2018-02-21 18:02 ` Linus Torvalds
2018-02-21 18:21 ` Andi Kleen
2018-02-21 19:47 ` Luck, Tony
2018-02-21 19:50 ` Linus Torvalds
2018-02-21 19:58 ` Luck, Tony
2018-02-21 20:40 ` Linus Torvalds
2018-02-22 1:45 ` [PATCH] efivarfs: Limit the rate for non-root to read files Luck, Tony
2018-02-22 1:58 ` Linus Torvalds
2018-02-22 5:34 ` Luck, Tony
2018-02-22 17:10 ` Eric W. Biederman
[not found] ` <CA+55aFy0hRexJkLbN7t31LjfGr4Ae0W5g6sBMqHHJi8aYuGKeA@mail.gmail.com>
[not found] ` <612E894E-62C8-4155-AED8-D53702EDC8DC@intel.com>
[not found] ` <CA+55aFxeBaTbwvbWqx1MKYjKKzLUs=1O43Bx2=JaO8qrnY-8HA@mail.gmail.com>
2018-02-22 17:15 ` [PATCH v2] " Luck, Tony
2018-02-22 17:39 ` Linus Torvalds
2018-02-22 17:54 ` Luck, Tony
2018-02-22 18:07 ` Linus Torvalds
2018-02-22 18:08 ` Ard Biesheuvel
2018-02-23 20:34 ` Andy Lutomirski
2018-02-23 19:47 ` [PATCH] " Peter Jones
2018-02-21 19:52 ` [PATCH 1/2] fs/efivarfs: restrict inode permissions Linus Torvalds
2018-02-24 20:06 ` Alan Cox
2018-02-25 10:56 ` Ard Biesheuvel
2018-02-21 0:49 ` Peter Jones
2018-02-20 23:19 ` Andy Lutomirski
2018-02-15 18:22 ` [PATCH 2/2] efi: restrict top-level attribute permissions Joe Konno
2018-02-16 10:41 ` [PATCH 0/2] efivars: reading variables can generate SMIs Ard Biesheuvel
2018-02-16 10:55 ` Borislav Petkov
2018-02-16 10:58 ` Ard Biesheuvel
2018-02-16 11:08 ` Borislav Petkov
2018-02-16 11:18 ` Ard Biesheuvel
2018-02-16 18:48 ` Joe Konno
2018-02-16 18:58 ` Borislav Petkov
2018-02-16 19:22 ` Peter Jones
2018-02-16 19:31 ` Ard Biesheuvel
2018-02-16 19:51 ` Matthew Garrett
2018-02-16 19:32 ` Luck, Tony
2018-02-16 19:54 ` Peter Jones
2018-02-16 20:51 ` James Bottomley
2018-02-16 21:09 ` Luck, Tony
2018-02-16 21:45 ` Andy Lutomirski
2018-02-16 21:58 ` Matthew Garrett
2018-02-16 22:02 ` Luck, Tony
2018-02-16 22:03 ` Matthew Garrett
2018-02-17 18:12 ` Andy Lutomirski
2018-02-16 22:05 ` Peter Jones
2018-02-17 9:36 ` Ard Biesheuvel
2018-02-17 16:17 ` Andi Kleen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=3908561D78D1C84285E8C5FCA982C28F7B37DB0F@ORSMSX110.amr.corp.intel.com \
--to=tony.luck@intel.com \
--cc=ak@linux.intel.com \
--cc=ard.biesheuvel@linaro.org \
--cc=james.bottomley@hansenpartnership.com \
--cc=jk@ozlabs.org \
--cc=joe.konno@linux.intel.com \
--cc=linux-efi@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@kernel.org \
--cc=mjg59@google.com \
--cc=pjones@redhat.com \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).