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| author | Dr. David Alan Gilbert <dgilbert@redhat.com> | 2021-02-24 19:56:25 +0000 |
|---|---|---|
| committer | Dr. David Alan Gilbert <dgilbert@redhat.com> | 2021-03-04 10:26:16 +0000 |
| commit | e586edcb410543768ef009eaa22a2d9dd4a53846 (patch) | |
| tree | 634df5a450305c9646de14a0fe22fc6b2760806a /docs | |
| parent | c40ae5a3ee387b13116948cbfe7824f03311db7e (diff) | |
| download | qemu-e586edcb410543768ef009eaa22a2d9dd4a53846.zip qemu-e586edcb410543768ef009eaa22a2d9dd4a53846.tar.gz qemu-e586edcb410543768ef009eaa22a2d9dd4a53846.tar.bz2 | |
virtiofs: drop remapped security.capability xattr as needed
On Linux, the 'security.capability' xattr holds a set of
capabilities that can change when an executable is run, giving
a limited form of privilege escalation to those programs that
the writer of the file deemed worthy.
Any write causes the 'security.capability' xattr to be dropped,
stopping anyone from gaining privilege by modifying a blessed
file.
Fuse relies on the daemon to do this dropping, and in turn the
daemon relies on the host kernel to drop the xattr for it. However,
with the addition of -o xattrmap, the xattr that the guest
stores its capabilities in is now not the same as the one that
the host kernel automatically clears.
Where the mapping changes 'security.capability', explicitly clear
the remapped name to preserve the same behaviour.
This bug is assigned CVE-2021-20263.
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Vivek Goyal <vgoyal@redhat.com>
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/tools/virtiofsd.rst | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/docs/tools/virtiofsd.rst b/docs/tools/virtiofsd.rst index 866b7db..00554c7 100644 --- a/docs/tools/virtiofsd.rst +++ b/docs/tools/virtiofsd.rst @@ -228,6 +228,10 @@ The 'map' type adds a number of separate rules to add **prepend** as a prefix to the matched **key** (or all attributes if **key** is empty). There may be at most one 'map' rule and it must be the last rule in the set. +Note: When the 'security.capability' xattr is remapped, the daemon has to do +extra work to remove it during many operations, which the host kernel normally +does itself. + xattr-mapping Examples ---------------------- |