bus: drop creds->capability_size

The number of available caps can be read from
/proc/sys/kernel/cap_last_cap during runtime. Our helper cap_last_cap()
does that, so there's no reason to remember the size of any capability
cache. We can just pre-allocate arrays with a suitable size for all
available caps and reject any higher caps.

The kernel capability API uses u32 as base so make sure we do the same.
Note that this is specified by POSIX, so it's unlikely to change.

1 files changed, 6 insertions, 2 deletions

diff --git a/src/libsystemd/sd-bus/bus-control.c b/src/libsystemd/sd-bus/bus-control.c
index e86546c343..b2394db3eb 100644
--- a/src/libsystemd/sd-bus/bus-control.c
+++ b/src/libsystemd/sd-bus/bus-control.c
@@ -33,6 +33,7 @@
 #include "bus-control.h"
 #include "bus-bloom.h"
 #include "bus-util.h"
+#include "capability.h"
 #include "cgroup-util.h"
 
 _public_ int sd_bus_get_unique_name(sd_bus *bus, const char **unique) {
@@ -520,8 +521,11 @@ static int bus_populate_creds_from_items(
                              SD_BUS_CREDS_INHERITABLE_CAPS | SD_BUS_CREDS_BOUNDING_CAPS) & mask;
 
                         if (m) {
-                                c->capability_size = item->size - offsetof(struct kdbus_item, caps.caps);
-                                c->capability = memdup(item->caps.caps, c->capability_size);
+                                if (item->caps.last_cap != cap_last_cap() ||
+                                    item->size - offsetof(struct kdbus_item, caps.caps) < DIV_ROUND_UP(item->caps.last_cap, 32U) * 4 * 4)
+                                        return -EBADMSG;
+
+                                c->capability = memdup(item->caps.caps, item->size - offsetof(struct kdbus_item, caps.caps));
                                 if (!c->capability)
                                         return -ENOMEM;