Lost time

Wednesday, August 9. 2006

So I wrote a blog entry, clicked "Save" and was brought to the login screen as apparently the session had timed out (how are you supposed to write a blog entry in a few minutes?). Anyway, I tried going back, but that only brought me to the login page again. OK, nothing is lost yet, I thought, the text is probably still somewhere in your 1GB of RAM. Now, how does one grep through his RAM? Of course /proc/kcore - I successfully did it for exactly the same kind of situation before, but this time it said:
cat: /proc/kcore: Operation not permitted
But I am root! How can I not be permitted to read? The permissions on the file were fine, so I looked at the kernel source and there it was:

static int open_kcore(struct inode * inode, struct file * filp)
{
return -EPERM;
}

Great! That can only be the works of some distribution patches (I'm using Kubuntu Dapper) and so I looked at the vanilla kernel source and found:

static int open_kcore(struct inode * inode, struct file * filp)
{
return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
}

So much for getting back at my blog entry.

I tried grepping through /proc/kcore on the server where s9y runs (which runs Kubuntu Breezy and doesn't have the stupid patch), hoping to find the POST data that was sent to apache, but no success.

Now I lost a few hours of my life only because of too short timeouts, and a stupid patch... I better go back to learning now.

PS: Before hitting the "Save" button I will copy the whole text into the clipboard!

Posted by Matthias Kretz in Linux at 22:13 | Comments (13) | Trackbacks (0)

Trackbacks

Trackback specific URI for this entry

No Trackbacks

Comments

Display comments as (Linear | Threaded)

In Konqueror if you hit "Back" it will restore also the context of the textboxes that you filled. Doesn't the browser that you use do the same?

#1 Andrei on 2006-08-09 22:35 (Reply)

I use Konqueror and I hit "Back" as I wrote above.

#1.1 Matthias Kretz (Homepage) on 2006-08-09 22:58 (Reply)

Well, I never encountered a case in which I couldn't get back to a page... and I suppose you are aware of the fact that the back button has a history that allows you to skip over the page that redirected you, and keeps redirecting you when you just hit "Back". But I'm not a blogger so I have no experience with this stuff

#1.1.1 Andrei on 2006-08-09 23:14 (Reply)

sometimes if you wait a really long time, the back button can't recover for you... it seems konq clears the page out of its cache eventually.

#1.1.1.1 Chani on 2006-08-10 01:46 (Reply)

Actually, what really happened, is the blog software has done a POST to bring up the entry page, and konqui reposted the data to bring up a fresh page. Nearly all browsers do this unless you go into offline mode.

#1.1.1.1.1 Aaron Krill (Homepage) on 2006-08-10 05:56 (Reply)

Actually from a short look at the s9y admin pages there was no POST involved until I hit "Save". But yes, there are some conditions - which I don't know - where going back in Konq will not go back to the page where you were.

#1.1.1.1.1.1 Matthias Kretz (Homepage) on 2006-08-10 16:33 (Reply)

It's sad to hear about your mishap.
Is this a new "feature" in 2.6.17? At least on my 2.6.16-ck11 both /dev/mem and /proc/kcore can be grepped.

#2 tuxophil (Homepage) on 2006-08-10 11:20 (Reply)

Like I said: this is not in the official kernel - it's only in Ubuntu kernels. See my bug report on launchpad: [url]https://launchpad.net/distros/ubuntu/+source/linux-source-2.6.15/+bug/55804[/url].

#2.1 Matthias Kretz (Homepage) on 2006-08-10 16:44 (Reply)

That sucks. It's about time it wasn't possible to lose that much work due to browsers. Back should be back, not check with the server that the site hasn't changed. But also I kinda feel that long pieces of text should be copied to some buffer and available in a menu somewhere.

I've long had the habit of copying to clipboard before posting. Back when I used IE I learnt this. Even to this day IE forgets everything in text fields as soon as you leave the page. Back gives you a blank set of fields.

#3 Max Howell (Homepage) on 2006-08-10 11:56 (Reply)

How about adding swap, forcing swapout of all unused pages by running some memory-eating app and then grepping through swap partition?

#4 klichota on 2006-08-10 16:51 (Reply)

I guess that would have overwritten my text as the memory holding it was probably deallocated in the mean time. Else it's a nice idea and a useful comment for the bugreport on launchpad.

#4.1 Matthias Kretz (Homepage) on 2006-08-10 17:08 (Reply)

I've had similar situation before.
Just coded a small app that eat up enough of ram to push the -- otherwise inactive -- konqueror to swap space, sync()'ed /dev/hda and rebooted.
Afterwards this was just a matter of grepping swap and extracting UTF-8

What brings to attention all the data you left on all the swapspaces >_>;;

#5 dexen deVries on 2006-08-11 14:58 (Reply)

It's in the Mandriva kernels too. I've just happened to write quite a lenghty reply on a forum, and then accidentally hit the "close tab" button on Firefox.

Seems to be a patch against rootkit usage, as it's also in the RedHat kernels.

#6 JarFil (Homepage) on 2006-11-06 05:44 (Reply)

Add Comment

Name
Email
Homepage
In reply to
Comment	E-Mail addresses will not be displayed and will only be used for E-Mail notifications To prevent automated Bots from commentspamming, please enter the string you see in the image below in the appropriate input box. Your comment will only be submitted if the strings match. Please ensure that your browser supports and accepts cookies, or your comment cannot be verified correctly. Enter the string from the spam-prevention image above: HTML-Tags will be converted to Entities. You can use [geshi lang=lang_name [,ln={y\|n}]][/lang] tags to embed source code snippets Standard emoticons like :-) and ;-) are converted to images.
	Remember Information? Subscribe to this entry