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init: fixed issues related to forking services 

Fixed issues related to forking services into new PID + mount
namespaces.

Remounting rootfs recursively as slave when creating a service in new
PID + mount namespaces. This prevents the service from interfering with
mount points in the parent namespace.

Unmount then mount /proc instead of mounting it with MS_REMOUNT, since
MS_REMOUNT is not sufficient to update /proc to the state appropriate
for the new PID namespace. Note that the /proc mount options specified
here are not the same as those used in the default mount namespace. I
kept them consistent with those used in the code prior to this fix.

Test: Used custom sleepd service to test init 'namespace' keyword.
Tested on angler in oreo-dev - I had to add PID namespaces to the
kernel (commit ad82c662).

Change-Id: I859104525f82fef3400d5abbad465331fc3d732f
This commit is contained in:
Joe Tanen 2017-10-25 08:07:26 -04:00 committed by Tom Cherry
parent 1c65e77e6d
commit 4bfdcb3932
1 changed files with 16 additions and 2 deletions
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18
init/service.cpp
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@ -101,8 +101,22 @@ static void SetUpPidNamespace(const std::string& service_name) {
// It's OK to LOG(FATAL) in this function since it's running in the first
// child process.
if (mount("", "/proc", "proc", kSafeFlags | MS_REMOUNT, "") == -1) {
PLOG(FATAL) << "couldn't remount(/proc) for " << service_name;
// Recursively remount / as slave like zygote does so unmounting and mounting /proc
// doesn't interfere with the parent namespace's /proc mount. This will also
// prevent any other mounts/unmounts initiated by the service from interfering
// with the parent namespace but will still allow mount events from the parent
// namespace to propagate to the child.
if (mount("rootfs", "/", nullptr, (MS_SLAVE | MS_REC), nullptr) == -1) {
PLOG(FATAL) << "couldn't remount(/) recursively as slave for " << service_name;
}
// umount() then mount() /proc.
// Note that it is not sufficient to mount with MS_REMOUNT.
if (umount("/proc") == -1) {
PLOG(FATAL) << "couldn't umount(/proc) for " << service_name;
}
if (mount("", "/proc", "proc", kSafeFlags, "") == -1) {
PLOG(FATAL) << "couldn't mount(/proc) for " << service_name;
}
if (prctl(PR_SET_NAME, service_name.c_str()) == -1) {