virtiofsd: drop CAP_DAC_READ_SEARCH

virtiofsd does not need CAP_DAC_READ_SEARCH because it already has
the more powerful CAP_DAC_OVERRIDE. Drop it from the list of
capabilities.

This is important because container runtimes may not include
CAP_DAC_READ_SEARCH by default. This patch allows virtiofsd to reduce
its capabilities when running inside a Docker container.

Note that CAP_DAC_READ_SEARCH may be necessary again in the future if
virtiofsd starts using open_by_handle_at(2).

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20200727190223.422280-2-stefanha@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
index a9feb90..784330e 100644 (file)
--- a/tools/virtiofsd/passthrough_ll.c
+++ b/tools/virtiofsd/passthrough_ll.c
@@ -2596,7 +2596,6 @@ static void setup_capabilities(char *modcaps_in)
     if (capng_updatev(CAPNG_ADD, CAPNG_PERMITTED | CAPNG_EFFECTIVE,
             CAP_CHOWN,
             CAP_DAC_OVERRIDE,
-            CAP_DAC_READ_SEARCH,
             CAP_FOWNER,
             CAP_FSETID,
             CAP_SETGID,