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When suid_dumpable == 2, set dumpable to 0 for apps

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Core dumps for zygote children are expected to be disabled in CTS, but
on system like Chrome OS, suid_dumpable is 2, thus not compliant with
CTS.  This patch sets dumpable to 0 for apps when suid_dumpable is 2.

Test: atest \
      android.permission.cts.FileSystemPermissionTest#testAllBlockDevicesAreSecure \
      android.os.cts.SecurityFeaturesTest#testPrctlDumpable \
      android.seccomp.cts.SeccompHostJUnit4DeviceTest#testCTSSyscallBlocked
Bug: 62379607
Bug: 79094505

Change-Id: Ida43b16590dca1e85a0f9549c779e38c00bc6a0c
This commit is contained in:
Victor Hsieh
2018-05-10 12:16:22 -07:00
parent 391d919622
commit e64594315b
1 changed files with 20 additions and 0 deletions
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20
core/jni/com_android_internal_os_Zygote.cpp
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@@ -704,6 +704,26 @@ static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArra
fail_fn(CREATE_ERROR("setresuid(%d) failed: %s", uid, strerror(errno)));
}
// The "dumpable" flag of a process, which controls core dump generation, is
// overwritten by the value in /proc/sys/fs/suid_dumpable when the effective
// user or group ID changes. See proc(5) for possible values. In most cases,
// the value is 0, so core dumps are disabled for zygote children. However,
// when running in a Chrome OS container, the value is already set to 2,
// which allows the external crash reporter to collect all core dumps. Since
// only system crashes are interested, core dump is disabled for app
// processes. This also ensures compliance with CTS.
int dumpable = prctl(PR_GET_DUMPABLE);
if (dumpable == -1) {
ALOGE("prctl(PR_GET_DUMPABLE) failed: %s", strerror(errno));
RuntimeAbort(env, __LINE__, "prctl(PR_GET_DUMPABLE) failed");
}
if (dumpable == 2 && uid >= AID_APP) {
if (prctl(PR_SET_DUMPABLE, 0, 0, 0, 0) == -1) {
ALOGE("prctl(PR_SET_DUMPABLE, 0) failed: %s", strerror(errno));
RuntimeAbort(env, __LINE__, "prctl(PR_SET_DUMPABLE, 0) failed");
}
}
if (NeedsNoRandomizeWorkaround()) {
// Work around ARM kernel ASLR lossage (http://b/5817320).
int old_personality = personality(0xffffffff);