Re: Gigantic memory leak in linux-2.6.[789]!

[Richard B. Johnson]

On Fri, 22 Oct 2004, Kasper Sandberg wrote:

> On Fri, 2004-10-22 at 16:13 +0200, Kristian Sørensen wrote:
> > Hi all!
> >
> > After some more testing after the previous post of the OOPS in
> > generic_delete_inode, we have now found a gigantic memory leak in Linux 2.6.
> > [789]. The scenario is the same:
> >
> > File system: EXT3
> > Unpack and delete linux-2.6.8.1.tar.bz2 with this Bash while loop:
> >
> > let "i = 0"
> > while [ "$i" -lt 10 ]; do
> >    tar jxf linux-2.6.8.1.tar.bz2;
> >    rm -fr linux-2.6.8.1;
> >    let "i = i + 1"
> > done
> >
> > When the loop has completed, the system use 124 MB memory more _each_ time....
> > so it is pretty easy to make a denial-of-service attack :-(


Do something like this with your favorite kernel version.....

while true ; do tar -xzf linux-2.6.9.tar.gz ; rm -rf linux-2.6.9 ; vmstat ; done

You can watch this for as long as you want. If there is no other
activity, the values reported by vmstat remain, on the average, stable.
If you throw in a `sync` command, the values rapidly converge to
little memory usage as the disk-data gets flused to disk.


> well.. i could understand if it used the total size of a unpacked linux
> kernel, even after the loop stopped, since it would just keep it cached,
> however, it might not be that case when it adds 124mb each time...
> > We have tried the same test on a RHEL WS 3 host (running a RedHat 2.4 kernel)
> > - and there is no problem.
> >
> >
> > Any deas?
>
> -
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Cheers,
Dick Johnson
Penguin : Linux version 2.6.9 on an i686 machine (5537.79 GrumpyMips).
                 98.36% of all statistics are fiction.