oss-sec mailing list archives
Re: CVE request: kernel: gdth: integer overflow in ioc_general()
From: Petr Matousek <pmatouse () redhat com>
Date: Tue, 9 Nov 2010 04:28:41 -0500 (EST)
----- "Dan Rosenberg" <dan.j.rosenberg () gmail 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 sizesUINT_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 () redhat 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 wouldtruncatethe size to 32 bits and allocate a small buffer. Then when we dothecopy_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=f63ae56e4e97fb12053590e41a4fa59e7daa74a4Credit: 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
Current thread:
- CVE request: kernel: gdth: integer overflow in ioc_general() Petr Matousek (Nov 08)
- Re: CVE request: kernel: gdth: integer overflow in ioc_general() Dan Rosenberg (Nov 08)
- Re: CVE request: kernel: gdth: integer overflow in ioc_general() Josh Bressers (Nov 10)
- <Possible follow-ups>
- Re: CVE request: kernel: gdth: integer overflow in ioc_general() Petr Matousek (Nov 09)
- Re: CVE request: kernel: gdth: integer overflow in ioc_general() Dan Rosenberg (Nov 09)