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libprocessgroup: make sure SetupCgroups is called once and only by init

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SetupCgroups is called by init process during early-init stage and is not
supposed to be called again by anyone else. Ensure that the caller is the
init process, make sure cgroup.rc file is written only one time, keep the
file descriptor to cgroup.rc file open by the init process to ensure all
its further mappings stay valid even if the file is deleted.

Bug: 124774415
Test: build, run, verify no errors or warning in the logcat

Change-Id: I70ccec551fc07c380333566f618b969667dcf783
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
This commit is contained in:
Suren Baghdasaryan 2019-03-21 17:10:09 -07:00
parent 443fdb2fdc
commit 798e805715
1 changed files with 19 additions and 3 deletions
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22
libprocessgroup/cgroup_map.cpp
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@ -229,9 +229,11 @@ static bool SetupCgroup(const CgroupDescriptor&) {
static bool WriteRcFile(const std::map<std::string, CgroupDescriptor>& descriptors) {
std::string cgroup_rc_path = StringPrintf("%s/%s", CGROUPS_RC_DIR, CgroupMap::CGROUPS_RC_FILE);
unique_fd fd(TEMP_FAILURE_RETRY(open(cgroup_rc_path.c_str(),
O_CREAT | O_WRONLY | O_TRUNC | O_CLOEXEC,
S_IRUSR | S_IRGRP | S_IROTH)));
// Let init keep the FD open to prevent file mappings from becoming invalid
// in case the file gets deleted somehow
static unique_fd fd(TEMP_FAILURE_RETRY(open(cgroup_rc_path.c_str(),
O_CREAT | O_WRONLY | O_TRUNC | O_CLOEXEC,
S_IRUSR | S_IRGRP | S_IROTH)));
if (fd < 0) {
PLOG(ERROR) << "open() failed for " << cgroup_rc_path;
return false;
@ -412,6 +414,19 @@ void CgroupMap::Print() const {
bool CgroupMap::SetupCgroups() {
std::map<std::string, CgroupDescriptor> descriptors;
if (getpid() != 1) {
LOG(ERROR) << "Cgroup setup can be done only by init process";
return false;
}
// Make sure we do this only one time. No need for std::call_once because
// init is a single-threaded process
static bool setup_done = false;
if (setup_done) {
LOG(WARNING) << "Attempt to call SetupCgroups more than once";
return true;
}
// load cgroups.json file
if (!ReadDescriptors(&descriptors)) {
LOG(ERROR) << "Failed to load cgroup description file";
@ -449,6 +464,7 @@ bool CgroupMap::SetupCgroups() {
return false;
}
setup_done = true;
return true;
}