CameraShm: Fix semaphore permission issue

When user created semaphore with mode 777, the actual mode of it may
not be expected because of umask. In this case, another non-root user
calling sem_open will get error EACCES then mSemLock is 0, which can
cause later segment fault. To avoid this, we directly change the
semaphore file mode to 0666 by chmod and add null check in lock().

Signed-off-by: Hao Yao <hao.yao@intel.com>

src/iutils/CameraShm.cpp

@@ -31,6 +31,7 @@ static const int CAMERA_IPCKEY = 0x43414D;
 static const int CAMERA_SHM_LOCK_TIME = 2;
 
 #define SEM_NAME "/camlock"
+#define SEM_FD_NAME "/dev/shm/sem.camlock"
 
 CameraSharedMemory::CameraSharedMemory()
         : mSemLock(nullptr),
@@ -211,7 +212,7 @@ bool CameraSharedMemory::processExist(pid_t pid, const char* storedName) {
 }
 
 void CameraSharedMemory::openSemLock() {
-    mSemLock = sem_open(SEM_NAME, O_CREAT | O_EXCL, 0777, 1);
+    mSemLock = sem_open(SEM_NAME, O_CREAT | O_EXCL, 0644, 1);
     if (mSemLock == SEM_FAILED) {
         mSemLock = sem_open(SEM_NAME, O_RDWR);
         if (mSemLock == SEM_FAILED) {
@@ -221,6 +222,7 @@ void CameraSharedMemory::openSemLock() {
             LOG1("Open the sem lock");
         }
     } else {
+        chmod(SEM_FD_NAME, 0666);
         LOG1("Create the sem lock");
         return;
     }
@@ -244,7 +246,12 @@ void CameraSharedMemory::openSemLock() {
         LOG1("Lock timed out, process holding it may have crashed. Re-create the semaphore.");
         sem_close(mSemLock);
         sem_unlink(SEM_NAME);
-        mSemLock = sem_open(SEM_NAME, O_CREAT | O_EXCL, 0777, 1);
+        mSemLock = sem_open(SEM_NAME, O_CREAT | O_EXCL, 0644, 1);
+        if (mSemLock == SEM_FAILED) {
+            LOGE("failed to re-create sem lock, errno: %s\n", strerror(errno));
+        } else {
+            chmod(SEM_FD_NAME, 0666);
+        }
     }
 }
 
@@ -255,9 +262,10 @@ void CameraSharedMemory::closeSemLock() {
 int CameraSharedMemory::lock() {
     int ret = OK;
     struct timespec ts;
-    CLEAR(ts);
+    CheckAndLogError(mSemLock == SEM_FAILED, BAD_VALUE, "invalid sem lock");
 
     // Wait the semaphore lock for 2 seconds
+    CLEAR(ts);
     clock_gettime(CLOCK_REALTIME, &ts);
     ts.tv_sec += CAMERA_SHM_LOCK_TIME;
     while (((ret = sem_timedwait(mSemLock, &ts)) == -1) && errno == EINTR) {