CVE-2013-2124 (published 2014-05-27T14:55Z)

Double free vulnerability in inspect-fs.c in LibguestFS 1.20.x before 1.20.7, 1.21.x, 1.22.0, and 1.23.0 allows remote attackers to cause a denial of service (crash) via empty guest files.

Severity: MEDIUM
CVSS v2 base score: 4.3 (AV:N/AC:M/Au:N/C:N/I:N/A:P)

Weakness information:
cwe_id: NVD-CWE-Other
cwe_name: Other
description: NVD is only using a subset of CWE for mapping instead of the entire CWE, and the weakness type is not covered by that subset.
extended_description: Insufficient Information

Fix information:
repo_url: https://github.com/libguestfs/libguestfs
commit_details: repo_url: https://github.com/libguestfs/libguestfs
author: Richard W.M. Jones
author_date: 2013-05-28 16:15:59+01:00
msg: inspection: Fix double-free when certain guest files are empty.

The following commit:

  commit 5a3da366268825b26b470cde35658b67c1d11cd4
  Author: Richard W.M. Jones <rjones@redhat.com>
  Date:   Thu Jan 24 17:07:38 2013 +0000

      inspect: Use CLEANUP_* macros in inspection code.

can cause a double-free along an error path when certain guest files
are empty where we expected those files to contain at least one line.

This causes virt-inspector to crash when run on these guests.

The following is a test case which demonstrates the crash.
`f20rawhidex64' is a Fedora guest, but with small adjustments to the
test you could use any Linux guest for this test.

  $ qemu-img create -f qcow2 -b f20rawhidex64 /tmp/test.qcow2
  Formatting '/tmp/test.qcow2', fmt=qcow2 size=21474836480 backing_file='f20rawhidex64' encryption=off cluster_size=65536 lazy_refcounts=off
  $ guestfish -i -a /tmp/test.qcow2 -- rm /etc/redhat-release : touch /etc/redhat-release
  $ virt-inspector /tmp/test.qcow2
  *** glibc detected *** virt-inspector: double free or corruption (fasttop): 0x00007f18bc9925a0 ***
  ======= Backtrace: =========
  /lib64/libc.so.6(+0x34ecc7ca8e)[0x7f18b8e64a8e]
  /lib64/libguestfs.so.0(+0x3f91898078)[0x7f18ba13c078]
  /lib64/libguestfs.so.0(+0x3f91899761)[0x7f18ba13d761]
  /lib64/libguestfs.so.0(+0x3f91896d12)[0x7f18ba13ad12]
  /lib64/libguestfs.so.0(+0x3f91894140)[0x7f18ba138140]
  /lib64/libguestfs.so.0(guestfs_inspect_os+0x35)[0x7f18ba0bcc35]
  virt-inspector(main+0x547)[0x7f18ba7c57d7]
  /lib64/libc.so.6(__libc_start_main+0xf5)[0x7f18b8e09a05]
  virt-inspector(+0x6665)[0x7f18ba7c7665]

This is a denial of service, but not likely to be exploitable.

(Found by Coverity)
repository: repo_url: https://github.com/libguestfs/libguestfs
repo_name: libguestfs/libguestfs
description: library and tools for accessing and modifying virtual machine disk images.  PLEASE DO NOT USE GITHUB FOR ISSUES OR PULL REQUESTS.  See the website for how to file a bug or contact us.
repo_language: C
owner: libguestfs
file_changes: filename: inspect-fs.c
change_type: ModificationType.MODIFY
diff: @@ -544,7 +544,7 @@ guestfs___check_package_management (guestfs_h *g, struct inspect_fs *fs)
 char *
 guestfs___first_line_of_file (guestfs_h *g, const char *filename)
 {
-  CLEANUP_FREE char **lines = NULL; /* sic: not CLEANUP_FREE_STRING_LIST */
+  char **lines = NULL; /* sic: not CLEANUP_FREE_STRING_LIST */
   int64_t size;
   char *ret;
 
@@ -573,6 +573,8 @@ guestfs___first_line_of_file (guestfs_h *g, const char *filename)
 
   ret = lines[0];               /* caller frees */
 
+  free (lines);
+
   return ret;
 }
 

programming_language: C