Allow system_server to attach bpf programs to tracepoints
In order to track time in state data using eBPF, system_server needs
to be able to attach BPF programs to tracepoints, which involves:
- calling perf_event_open and the PERF_EVENT_IOC_SET_BPF ioctl
- running BPF programs
- reading tracepoint ids from tracefs
Grant system_server the necessary permissions for these tasks
Test: modify system_server to try to attach programs; check for
denials
Bug: 138317993
Change-Id: I07dafd325a9c57d53767a09d4ca7b0fb2dd2d328
Signed-off-by: Connor O'Brien <connoro@google.com>
diff --git a/private/bpfloader.te b/private/bpfloader.te
index 00d4c79..34921e6 100644
--- a/private/bpfloader.te
+++ b/private/bpfloader.te
@@ -18,7 +18,7 @@
### Neverallow rules
###
neverallow { domain -bpfloader } *:bpf { map_create prog_load };
-neverallow { domain -bpfloader -netd -netutils_wrapper } *:bpf prog_run;
+neverallow { domain -bpfloader -netd -netutils_wrapper -system_server } *:bpf prog_run;
neverallow { domain -bpfloader -init } bpfloader_exec:file { execute execute_no_trans };
neverallow bpfloader domain:{ tcp_socket udp_socket rawip_socket } *;
# only system_server, netd and bpfloader can read/write the bpf maps
diff --git a/private/coredomain.te b/private/coredomain.te
index 44052c3..0c84797 100644
--- a/private/coredomain.te
+++ b/private/coredomain.te
@@ -132,6 +132,7 @@
-init
-traced_probes
-shell
+ -system_server
-traceur_app
} debugfs_tracing:file no_rw_file_perms;
diff --git a/private/system_server.te b/private/system_server.te
index be2eec6..2a07a1f 100644
--- a/private/system_server.te
+++ b/private/system_server.te
@@ -896,6 +896,9 @@
allow system_server debugfs_wifi_tracing:dir search;
allow system_server debugfs_wifi_tracing:file rw_file_perms;
+# Allow system_server to read tracepoint ids in order to attach BPF programs to them.
+allow system_server debugfs_tracing:file r_file_perms;
+
# allow system_server to exec shell, asanwrapper & zygote(app_process) on ASAN builds. Needed to run
# asanwrapper.
with_asan(`
@@ -905,10 +908,11 @@
')
# allow system_server to read the eBPF maps that stores the traffic stats information and update
-# the map after snapshot is recorded
+# the map after snapshot is recorded, and to read, update and run the maps and programs used for
+# time in state accounting
allow system_server fs_bpf:dir search;
allow system_server fs_bpf:file { read write };
-allow system_server bpfloader:bpf { map_read map_write };
+allow system_server bpfloader:bpf { map_read map_write prog_run };
# ART Profiles.
# Allow system_server to open profile snapshots for read.
@@ -1122,3 +1126,8 @@
set_prop(system_server, binder_cache_system_server_prop)
neverallow { domain -system_server -init }
binder_cache_system_server_prop:property_service set;
+
+# Allow system server to attach BPF programs to tracepoints. Deny read permission so that
+# system_server cannot use this access to read perf event data like process stacks.
+allow system_server self:perf_event { open write cpu kernel };
+neverallow system_server self:perf_event ~{ open write cpu kernel };