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Hello community,
here is the log from the commit of package kvm_stat for openSUSE:Factory
checked in at 2022-10-28 19:32:06
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Comparing /work/SRC/openSUSE:Factory/kvm_stat (Old)
and /work/SRC/openSUSE:Factory/.kvm_stat.new.2275 (New)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Package is "kvm_stat"
Fri Oct 28 19:32:06 2022 rev:21 rq:1031978 version:MACRO
Changes:
--------
--- /work/SRC/openSUSE:Factory/kvm_stat/kvm_stat.changes 2022-09-02
21:57:17.668405608 +0200
+++ /work/SRC/openSUSE:Factory/.kvm_stat.new.2275/kvm_stat.changes
2022-10-28 19:32:32.899539410 +0200
@@ -1,0 +2,7 @@
+Fri Oct 28 14:24:29 UTC 2022 - Dario Faggioli <dfaggi...@suse.com>
+
+- Fix security issue about debugfs described in bsc#1202924
+ * Added patches:
+ tools-kvm_stat-fix-attack-vector-with-user-controlle.patch
+
+-------------------------------------------------------------------
New:
----
tools-kvm_stat-fix-attack-vector-with-user-controlle.patch
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Other differences:
------------------
++++++ kvm_stat.spec ++++++
--- /var/tmp/diff_new_pack.kZRNBJ/_old 2022-10-28 19:32:33.399541917 +0200
+++ /var/tmp/diff_new_pack.kZRNBJ/_new 2022-10-28 19:32:33.403541937 +0200
@@ -47,6 +47,8 @@
Patch06: add-command-line-switch-L-to-log-file.patch
Patch07: add-sample-systemd-unit.patch
Patch08: add-restart-delay.patch
+# PAtch 09 is for bsc#1202924
+Patch09: tools-kvm_stat-fix-attack-vector-with-user-controlle.patch
%define XXX This package provides a userspace tool "kvm_stat", which displays
KVM vm exit \
information as a means of monitoring vm behavior. The data is taken from the\
@@ -85,6 +87,7 @@
%patch07 -p1
%patch08 -p1
%endif
+%patch09 -p1
%build
make -C tools/kvm/kvm_stat %{?_smp_mflags}
++++++ tools-kvm_stat-fix-attack-vector-with-user-controlle.patch ++++++
>From 210cdcac0d41a340475400b852fb1cb43182c349 Mon Sep 17 00:00:00 2001
From: Matthias Gerstner <matthias.gerst...@suse.de>
Date: Thu, 1 Sep 2022 15:34:00 +0200
Subject: [PATCH] tools/kvm_stat: fix attack vector with user controlled FUSE
mounts
The first field in /proc/mounts can be influenced by unprivileged users
through the widespread `fusermount` setuid-root program. Example:
```
user$ mkdir ~/mydebugfs
user$ export _FUSE_COMMFD=0
user$ fusermount ~/mydebugfs -ononempty,fsname=debugfs
user$ grep debugfs /proc/mounts
debugfs /home/user/mydebugfs fuse
rw,nosuid,nodev,relatime,user_id=1000,group_id=100 0 0
```
If there is no debugfs already mounted in the system then this can be
used by unprivileged users to trick kvm_stat into using a user
controlled file system location for obtaining KVM statistics.
To exploit this also a race condition has to be won, since the code
checks for the existence of the 'kvm' subdirectory of the resulting
path. This doesn't work on a FUSE mount, because the root user is not
allowed to access non-root FUSE mounts for security reasons. If an
attacker manages to unmount the FUSE mount in time again then kvm_stat
would be using the resulting path, though.
The impact if winning the race condition is mostly a denial-of-service
or damaged information integrity. The files in debugfs are only opened
for reading. So the attacker can cause very large data to be read in by
kvm_stat or fake data to be processed by kvm_stat. I don't see any
viable way to turn this into a privilege escalation.
The fix is simply to use the file system type field instead. Whitespace
in the mount path is escaped in /proc/mounts thus no further safety
measures in the parsing should be necessary to make this correct.
---
tools/kvm/kvm_stat/kvm_stat | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/kvm/kvm_stat/kvm_stat b/tools/kvm/kvm_stat/kvm_stat
index 9c366b3a676d..88a73999aa58 100755
--- a/tools/kvm/kvm_stat/kvm_stat
+++ b/tools/kvm/kvm_stat/kvm_stat
@@ -1756,7 +1756,7 @@ def assign_globals():
debugfs = ''
for line in open('/proc/mounts'):
- if line.split(' ')[0] == 'debugfs':
+ if line.split(' ')[2] == 'debugfs':
debugfs = line.split(' ')[1]
break
if debugfs == '':
--
2.35.1
