commit 2055ebfe01eff48ec8ef1eb0d5ae233a0c036e42
author Tom Cherry <tomcherry@google.com> Mon Jun 22 10:15:04 2020 -0700
committer Tom Cherry <tomcherry@google.com> Mon Jun 22 14:57:43 2020 -0700
tree 5b7542926a03d5355b0f007a7478d16813adb33b
parent 921451fbb468c1d5076f908033044779941e5aa8

logd: make drop_privs work if neither klogd or auditd are used

Fix a bug that was causing cap_set_flag() fail and logd to exit.

Bug: 159588327
Test: caps are set correctly and logd functions with both, one of, or
      none of klogd and auditd enabled.
Merged-In: Ia51f078ad848535ce1ac29edd8a56a2b686a12cc
Change-Id: Ia51f078ad848535ce1ac29edd8a56a2b686a12cc
(cherry picked from commit 54b00a9e3cb61e090c5ff9403eedd6add55b48b1)

logd/main.cpp

diff --git a/logd/main.cpp b/logd/main.cpp
index 23bbf86..acf9a07 100644
--- a/logd/main.cpp
+++ b/logd/main.cpp
@@ -62,14 +62,13 @@
 // has a 'sigstop' feature that sends SIGSTOP to a service immediately before calling exec().  This
 // allows debuggers, etc to be attached to logd at the very beginning, while still having init
 // handle the user, groups, capabilities, files, etc setup.
-static int drop_privs(bool klogd, bool auditd) {
-    sched_param param = {};
-
+static int DropPrivs(bool klogd, bool auditd) {
     if (set_sched_policy(0, SP_BACKGROUND) < 0) {
         android::prdebug("failed to set background scheduling policy");
         return -1;
     }
 
+    sched_param param = {};
     if (sched_setscheduler((pid_t)0, SCHED_BATCH, &param) < 0) {
         android::prdebug("failed to set batch scheduler");
         return -1;
@@ -84,21 +83,24 @@
 
     std::unique_ptr<struct _cap_struct, int (*)(void*)> caps(cap_init(), cap_free);
     if (cap_clear(caps.get()) < 0) {
+        android::prdebug("cap_clear() failed");
         return -1;
     }
-    std::vector<cap_value_t> cap_value;
     if (klogd) {
-        cap_value.emplace_back(CAP_SYSLOG);
+        cap_value_t cap_syslog = CAP_SYSLOG;
+        if (cap_set_flag(caps.get(), CAP_PERMITTED, 1, &cap_syslog, CAP_SET) < 0 ||
+            cap_set_flag(caps.get(), CAP_EFFECTIVE, 1, &cap_syslog, CAP_SET) < 0) {
+            android::prdebug("Failed to set CAP_SYSLOG");
+            return -1;
+        }
     }
     if (auditd) {
-        cap_value.emplace_back(CAP_AUDIT_CONTROL);
-    }
-
-    if (cap_set_flag(caps.get(), CAP_PERMITTED, cap_value.size(), cap_value.data(), CAP_SET) < 0) {
-        return -1;
-    }
-    if (cap_set_flag(caps.get(), CAP_EFFECTIVE, cap_value.size(), cap_value.data(), CAP_SET) < 0) {
-        return -1;
+        cap_value_t cap_audit_control = CAP_AUDIT_CONTROL;
+        if (cap_set_flag(caps.get(), CAP_PERMITTED, 1, &cap_audit_control, CAP_SET) < 0 ||
+            cap_set_flag(caps.get(), CAP_EFFECTIVE, 1, &cap_audit_control, CAP_SET) < 0) {
+            android::prdebug("Failed to set CAP_AUDIT_CONTROL");
+            return -1;
+        }
     }
     if (cap_set_proc(caps.get()) < 0) {
         android::prdebug("failed to set CAP_SYSLOG or CAP_AUDIT_CONTROL (%d)", errno);
@@ -332,7 +334,7 @@
     }
 
     bool auditd = __android_logger_property_get_bool("ro.logd.auditd", BOOL_DEFAULT_TRUE);
-    if (drop_privs(klogd, auditd) != 0) {
+    if (DropPrivs(klogd, auditd) != 0) {
         return EXIT_FAILURE;
     }