Coda Filesystem Kernel Memory Disclosure
| Release Date | 2010-08-16 |
| Application | Coda kernel module for NetBSD and FreeBSD |
| Versions | All known versions |
| Severity | Medium |
| Discovered by | Dan Rosenberg <drosenberg {at} vsecurity.com> |
| Vendor Status | Patch Released [2][3] |
| CVE Candidate | CVE-2010-3014 |
| Reference | Original Advisory |
Product Description
From [1]:
"Coda is a distributed filesystem with is origin in AFS2. It has many features that are very desirable for network filesystems. Currently, Coda has several features not found elsewhere.
Vulnerability Overview
On July 19th, VSR identified a vulnerability in the Coda filesystem kernel module, as implemented for FreeBSD and NetBSD. By sending a specially crafted ioctl request to a mounted Coda filesystem, an unprivileged local user could read large portions of kernel heap memory, leading to the disclosure of potentially sensitive information.
Product Background
Coda is implemented as a kernel filesystem module with userland components. System calls involving file I/O are passed to the Coda kernel module, which in turn passes the request to the userland Venus cache manager via a character device. Venus answers the request by checking its cache or requesting content from the Coda server. Coda implements most standard filesystem operations, including providing an ioctl interface.
Vulnerability Details
Coda ioctls are passed through the Coda filesystem module before being sent to
Venus. The arguments to a Coda ioctl are encapsulated in a
PioctlData struct, which in turn contains a ViceIoctl
struct. The ViceIoctl struct contains in_size and
out_size fields, dictating the expected size of the input and
output data corresponding to a particular ioctl request. The
in_size field is validated to prevent memory corruption via
copying an unexpected amount of data from userspace into a kernel buffer.
However, the out_size field was missing this validation. When
copying the output data of an ioctl request back to userspace, the
out_size field was used to determine the amount of data to copy,
without restricting it to a maximum possible size. By specifying a large value
for this field, the contents of the kernel heap beyond the data intended to be
returned to the user would be copied into a userland buffer. An unprivileged
user could exploit this to read large portions of the kernel heap, potentially
disclosing sensitive information.
Versions Affected
This vulnerability affects all known versions of the Coda filesystem module as included in FreeBSD and NetBSD. The Linux Coda module is not affected.
Vendor Response
The following timeline details FreeBSD's and NetBSD's response to the reported issue:
| 2010-07-19 | Vulnerability reported to FreeBSD and NetBSD |
| 2010-07-20 | Fix committed by NetBSD [2] |
| 2010-07-21 | Response from FreeBSD |
| 2010-07-21 | FreeBSD and NetBSD provided a draft advisory |
| 2010-08-05 | Fix committed by FreeBSD [3] |
| 2010-08-16 | Coordinated disclosure |
Recommendation
Coda users should apply the updates committed by NetBSD [2] and FreeBSD [3].
Common Vulnerabilities and Exposures (CVE) Information
The Common Vulnerabilities and Exposures (CVE) project has assigned the number CVE-2010-3014 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org), which standardizes names for security problems.
Acknowledgements
Thanks to the FreeBSD and NetBSD security teams for their prompt responses.
References
| 1. | Coda File System http://www.coda.cs.cmu.edu |
| 2. | Coda module in NetBSD CVS http://cvsweb.netbsd.org/bsdweb.cgi/src/sys/coda/?only_with_tag=MAIN |
| 3. | FreeBSD SVN revision 210997 http://svn.freebsd.org/viewvc/base?view=revision&revision=210997 |
This advisory is distributed for educational purposes only with the sincere hope that it will help promote public safety. This advisory comes with absolutely NO WARRANTY; not even the implied warranty of merchantability or fitness for a particular purpose. Virtual Security Research, LLC nor the author accepts any liability for any direct, indirect, or consequential loss or damage arising from use of, or reliance on, this information.
See the VSR disclosure policy for more information on our responsible disclosure practices.
Copyright 2010 Virtual Security Research, LLC. All rights reserved.
