From 45dab78e989a8e3f3cabb71ebc753e5a8fdcbcd6 Mon Sep 17 00:00:00 2001
From: Josh Gao <jmgao@google.com>
Date: Wed, 1 Feb 2017 14:56:09 -0800
Subject: [PATCH] zygote: make all capabilities inheritable.

Set CapInh to the full set of permitted capabilities, so that the crash
handler can raise ambient capabilities to allow crash_dump to ptrace
zygote-descended children without needing CAP_SYS_PTRACE. CapInh is
restricted by filesystem capabilities if the ambient capability set
hasn't been raised, so this should only have an effect when ambient
capabilities are modified.

Bug: http://b/34853272
Test: debuggerd -b `pidof system_server`
Change-Id: I27d2aa4ab4fc47a183ce2b254be178de4d58840c
---
 core/jni/com_android_internal_os_Zygote.cpp | 33 +++++++++++++++++++--
 1 file changed, 30 insertions(+), 3 deletions(-)

diff --git a/core/jni/com_android_internal_os_Zygote.cpp b/core/jni/com_android_internal_os_Zygote.cpp
index a32dbad7838ff..3498108991fa1 100644
--- a/core/jni/com_android_internal_os_Zygote.cpp
+++ b/core/jni/com_android_internal_os_Zygote.cpp
@@ -253,13 +253,36 @@ static void DropCapabilitiesBoundingSet(JNIEnv* env) {
         ALOGE("prctl(PR_CAPBSET_DROP) failed with EINVAL. Please verify "
               "your kernel is compiled with file capabilities support");
       } else {
+        ALOGE("prctl(PR_CAPBSET_DROP, %d) failed: %s", i, strerror(errno));
         RuntimeAbort(env, __LINE__, "prctl(PR_CAPBSET_DROP) failed");
       }
     }
   }
 }
 
-static void SetCapabilities(JNIEnv* env, int64_t permitted, int64_t effective) {
+static void SetInheritable(JNIEnv* env, uint64_t inheritable) {
+  __user_cap_header_struct capheader;
+  memset(&capheader, 0, sizeof(capheader));
+  capheader.version = _LINUX_CAPABILITY_VERSION_3;
+  capheader.pid = 0;
+
+  __user_cap_data_struct capdata[2];
+  if (capget(&capheader, &capdata[0]) == -1) {
+    ALOGE("capget failed: %s", strerror(errno));
+    RuntimeAbort(env, __LINE__, "capget failed");
+  }
+
+  capdata[0].inheritable = inheritable;
+  capdata[1].inheritable = inheritable >> 32;
+
+  if (capset(&capheader, &capdata[0]) == -1) {
+    ALOGE("capset(inh=%" PRIx64 ") failed: %s", inheritable, strerror(errno));
+    RuntimeAbort(env, __LINE__, "capset failed");
+  }
+}
+
+static void SetCapabilities(JNIEnv* env, uint64_t permitted, uint64_t effective,
+                            uint64_t inheritable) {
   __user_cap_header_struct capheader;
   memset(&capheader, 0, sizeof(capheader));
   capheader.version = _LINUX_CAPABILITY_VERSION_3;
@@ -271,9 +294,12 @@ static void SetCapabilities(JNIEnv* env, int64_t permitted, int64_t effective) {
   capdata[1].effective = effective >> 32;
   capdata[0].permitted = permitted;
   capdata[1].permitted = permitted >> 32;
+  capdata[0].inheritable = inheritable;
+  capdata[1].inheritable = inheritable >> 32;
 
   if (capset(&capheader, &capdata[0]) == -1) {
-    ALOGE("capset(%" PRId64 ", %" PRId64 ") failed", permitted, effective);
+    ALOGE("capset(perm=%" PRIx64 ", eff=%" PRIx64 ", inh=%" PRIx64 ") failed: %s", permitted,
+          effective, inheritable, strerror(errno));
     RuntimeAbort(env, __LINE__, "capset failed");
   }
 }
@@ -508,6 +534,7 @@ static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArra
       EnableKeepCapabilities(env);
     }
 
+    SetInheritable(env, permittedCapabilities);
     DropCapabilitiesBoundingSet(env);
 
     bool use_native_bridge = !is_system_server && (instructionSet != NULL)
@@ -580,7 +607,7 @@ static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArra
         }
     }
 
-    SetCapabilities(env, permittedCapabilities, effectiveCapabilities);
+    SetCapabilities(env, permittedCapabilities, effectiveCapabilities, permittedCapabilities);
 
     SetSchedulerPolicy(env);