linux-kernel - Re: [RFC] swap image signature check upon resume

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Message-Id: <200712062246.49422.rjw@sisk.pl>
Date:	Thu, 6 Dec 2007 22:46:48 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	bbpetkov@...oo.de
Cc:	Pavel Machek <pavel@...e.cz>, linux-kernel@...r.kernel.org
Subject: Re: [RFC] swap image signature check upon resume

On Thursday, 6 of December 2007, Borislav Petkov wrote:
> Hi Pavel,
> hi Rafael,
> 
> after a quick search i couldn't find anything dealing with the topic in the
> subject line so here we go:
> 
> One sometimes can mix up (and by one i mean me) the
> kernel images one boots after having suspended the machine previously. There can
> be at least two reasons for that:
> 
> 1. too many kernels in grub and having forgotten with which i suspended.
> 2. compile and install a new kernel and forget about it, suspend in the evening
> and then boot with the new kernel;
> 
> in both cases you end up staring at fsck since they filesystems haven't been unmounted,
> of course. Or at least see the warning message of some journal recovery whisk away.
> 
> In order to alleviate that, one could probably go, imho, and write in the swsusp_header
> the kernel version which suspended the machine (UTS_RELEASE) alongside
> SWSUSP_SIG and check that against the kernel version of the image just booting.
> If they match then all is well, if not, one could
> 
> a) issue a BIG FAT WARNING and reboot telling the user to select the proper
> image
> b) ask the user what to do:
> 	- proceed as if "noresume" has been entered on the kernel command line
> 	- reboot after issuing the kernel version which suspended the machine
> 	-
> c)...
> 
> In case you guys think something like that might be of use i can come up with a
> patch in the next coupla days...

Well, there's a patchset in the current mainline that allows you to use
arbitrary (sufficiently new) kernel to load the image and then restore the
image kernel.  So, you can hibernate 2.6.24-rc3 and use 2.6.24-rc2 to restore
it, for example.

I'm going to do that for i386 too.

Greetings,
Rafael
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