linux-kernel - Re: [PATCH v2 3/5] efi_pstore: Remove a logic erasing entries from a write callback to hold multiple logs

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <CAGTjWtAUv=HzOGPDeDuTb_6z81bnSQ-F7DDERZ2tqmfaP4wXwQ@mail.gmail.com>
Date:	Thu, 25 Oct 2012 13:21:48 -0700
From:	Mike Waychison <mikew@...gle.com>
To:	Seiji Aguchi <seiji.aguchi@....com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"Luck, Tony (tony.luck@...el.com)" <tony.luck@...el.com>,
	"Matthew Garrett (mjg@...hat.com)" <mjg@...hat.com>,
	"dzickus@...hat.com" <dzickus@...hat.com>,
	"dle-develop@...ts.sourceforge.net" 
	<dle-develop@...ts.sourceforge.net>,
	Satoru Moriya <satoru.moriya@....com>
Subject: Re: [PATCH v2 3/5] efi_pstore: Remove a logic erasing entries from a
 write callback to hold multiple logs

On Thu, Oct 25, 2012 at 1:03 PM, Seiji Aguchi <seiji.aguchi@....com> wrote:
>> > -               list_del(&found->list);
>> > +       sprintf(name, "dump-type%u-%u-%lu", type, part,
>> > +               get_seconds());
>>
>> Actually, nothing seems to be ensuring that the value used here ends up being the same as the ctime :\  Consider what happens if the
>> get_seconds() call here happens at second N, and the i_ctime is collected at time N+1. The object wouldn't be able to be deleted after
>> patch 4/5 is applied.  How can we better ensure that the i_ctime is the same value as serialized into the efi var name here?
>
>  i_ctime of pstore file system is different from normal file systems.
> As I said in patch v1, i_ctime of pstore means the date that the record was "originally" stored.
>
> I_ctime is always set to N.
> Here is the scenario.
>
> 1.  writing time
>     - get_seconds() call here happens at second N
>     - "N" is stored to a variable name
>
> 2. System reboots...
> 3. System boots up...
>
> 4. reading time
>    - pstore calls a read callback, efi_pstore_read()
>    -  efi_pstore_read extracts ctime, "N", from the virable name

Ah, I accidentally glossed over this bit.  Thanks for correcting me :)

>    -  efi_pstore passes "N" to pstore file system
>     - pstore create a file, /dev/pstore/dmesg* and set "N" to i_ctime
>
> Pstore file system doesn't set i_ctime by itself but set ctime passed by platform drivers.
>

So doesn't this break erasing of existing dumps in pstore-efivars?
Unless efi_pstore_read still understands the older variable name
formats, users will be stranded with dumps consuming space in efivars
that aren't exported via pstore anymore.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/