linux-kernel - Re: [PATCH] pstore: Fix an overflow on 32-bit builds.

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Date:	Wed, 18 Jun 2014 09:35:55 +0100
From:	Matt Fleming <matt@...sole-pimps.org>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Andrzej Zaborowski <andrew.zaborowski@...el.com>,
	Matt Fleming <matt.fleming@...el.com>,
	Madper Xie <cxie@...hat.com>,
	Anton Vorontsov <anton@...msg.org>,
	Colin Cross <ccross@...roid.com>,
	Kees Cook <keescook@...omium.org>,
	Tony Luck <tony.luck@...el.com>, linux-efi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pstore: Fix an overflow on 32-bit builds.

On Mon, 09 Jun, at 01:24:43PM, David Rientjes wrote:
> On Mon, 9 Jun 2014, Andrzej Zaborowski wrote:
> 
> > [resend]
> > In generic_id the long int timestamp is multiplied by 100000 and needs
> > an explicit cast to u64.
> > 
> > Without that the id in the resulting pstore filename is wrong and
> > userspace may have problems parsing it, but more importantly files in
> > pstore can never be deleted and may fill the EFI flash (brick device?).
> > This happens because when generic pstore code wants to delete a file,
> > it passes the id to the EFI backend which reinterpretes it and a wrong
> > variable name is attempted to be deleted.  There's no error message but
> > after remounting pstore, deleted files would reappear.

It shouldn't be possible to brick devices because the efi-pstore code
still goes through efivar_entry_set_safe() whic has the necessary
checks. Please let me know if you've witnessed any fallout from this bug
other than being unable to delete files.

> This fixes commit fdeadb43fdf1 ("efi-pstore: Make efi-pstore return a 
> unique id") that went into stable, so I'm not sure if this should go into 
> stable as well.
 
I think it should go to stable too. Tony?

> You probably had to resend this because you didn't email any of the 
> maintainers (fixed).  Use scripts/get_maintainer.pl to figure out who to 
> email about a patch.

Thanks for triaging this David.

Unless anyone speaks up I'm going to throw this into the EFI tree with
David's Acked-by.

-- 
Matt Fleming, Intel Open Source Technology Center
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