Openwall GNU/*/Linux - a small security-enhanced Linux distro for servers
[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Date: Tue, 9 Nov 2010 04:28:41 -0500 (EST)
From: Petr Matousek <pmatouse@...hat.com>
To: Dan Rosenberg <dan.j.rosenberg@...il.com>
Cc: coley@...us.mitre.org, oss-security@...ts.openwall.com
Subject: Re: CVE request: kernel: gdth: integer overflow in
 ioc_general()

----- "Dan Rosenberg" <dan.j.rosenberg@...il.com> wrote:

> This is not actually a security issue.  See the code:
> 
> ...
> if (!(buf = gdth_ioctl_alloc(ha, gen.data_len + gen.sense_len,
>                                      FALSE, &paddr)))
>             return -EFAULT;
> if (copy_from_user(buf, arg + sizeof(gdth_ioctl_general),
>                            gen.data_len + gen.sense_len)) {
> ...
> 
> If gen.data_len + gen.sense_len > UINT_MAX, then a small buffer will
> be allocated.  But then the copy_from_user() will always fault before
> copying any data over because the access_ok() check will fail on
> sizes
> > UINT_MAX.  It's definitely a bug, but not a vulnerability.

#define SIZE 0x10000029aUL

...
    volatile unsigned long t = SIZE;  // volatile so that it does not get optimised (error)

    printk("nada: %lx\n", current_thread_info()->addr_limit.seg);
    printk("nada2: %lx\n", access_ok(VERIFY_READ, 0, t));
    printk("nada3: %lx\n", t);
    printk("nada4: %lx\n", t > UINT_MAX);
...

nada: ffff810000000000
nada2: 1
nada3: 10000029a
nada4: 1

> 
> On Mon, Nov 8, 2010 at 5:02 PM, Petr Matousek <pmatouse@...hat.com>
> wrote:
> > "gdth_ioctl_alloc() takes the size variable as an int.
> > copy_from_user() takes the size variable as an unsigned long.
> > gen.data_len and gen.sense_len are unsigned longs.
> > On x86_64 longs are 64 bit and ints are 32 bit.
> >
> > We could pass in a very large number and the allocation would
> truncate
> > the size to 32 bits and allocate a small buffer.  Then when we do
> the
> > copy_from_user(), it would result in a memory corruption."
> >
> > Upstream commit:
> >
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=f63ae56e4e97fb12053590e41a4fa59e7daa74a4
> >
> > Credit: James E.J. Bottomley
> >
> > Reference:
> > http://ns3.spinics.net/lists/linux-scsi/msg47361.html
> > https://bugzilla.redhat.com/show_bug.cgi?id=651147
> >
> > Thanks,
> > --
> > Petr Matousek / Red Hat Security Response Team
> >

Powered by blists - more mailing lists

Your e-mail address:

Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.