a59feb483b
virtiofsd runs as root but only needs a subset of root's Linux
capabilities(7). As a file server its purpose is to create and access
files on behalf of a client. It needs to be able to access files with
arbitrary uid/gid owners. It also needs to be create device nodes.
Introduce a Linux capabilities(7) whitelist and drop all capabilities
that we don't need, making the virtiofsd process less powerful than a
regular uid root process.
# cat /proc/PID/status
...
Before After
CapInh: 0000000000000000 0000000000000000
CapPrm: 0000003fffffffff 00000000880000df
CapEff: 0000003fffffffff 00000000880000df
CapBnd: 0000003fffffffff 0000000000000000
CapAmb: 0000000000000000 0000000000000000
Note that file capabilities cannot be used to achieve the same effect on
the virtiofsd executable because mount is used during sandbox setup.
Therefore we drop capabilities programmatically at the right point
during startup.
This patch only affects the sandboxed child process. The parent process
that sits in waitpid(2) still has full root capabilities and will be
addressed in the next patch.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20200416164907.244868-2-stefanha@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
|
||
|---|---|---|
| .. | ||
| virtiofsd | ||