damn. We need root privilages to do semaphore operations even if we

have done the semget() as root.  The problem is that become_root() and
unbecome_root() are so slow!

I've provided two options. The default is to set the semaphores (but
_not_ the shared memory) world writeable so that a become_root() isn't
needed. Otherwise you can define SECURE_SEMAPHORES and pay the
performance penalty.

diff --git a/source/locking/shmem_sysv.c b/source/locking/shmem_sysv.c
index e3f40418d97e4b014299e06bbe388fb66e1a1bf3..8832902820a23bb2172430d84750006fea79d48d 100644 (file)
--- a/source/locking/shmem_sysv.c
+++ b/source/locking/shmem_sysv.c
@@ -39,6 +39,14 @@ extern int DEBUGLEVEL;
 #define IPC_PERMS 0644
 #endif
 
+#ifdef SECURE_SEMAPHORES
+/* secure semaphores are slow because we have to do a become_root()
+   on every call! */
+#define SEMAPHORE_PERMS IPC_PERMS
+#else
+#define SEMAPHORE_PERMS 0666
+#endif
+
 #ifdef SEMMSL
 #define SHMEM_HASH_SIZE (SEMMSL-1)
 #else
@@ -92,45 +100,49 @@ static BOOL shm_initialize_called = False;
 
 static int read_only;
 
-static BOOL sem_lock(int i)
+static BOOL sem_change(int i, int op)
 {
+#ifdef SECURE_SEMAPHORES
+       extern struct current_user current_user;
+       int became_root=0;
+#endif
        struct sembuf sb;
+       int ret;
+
        if (read_only) return True;
-       
-       sb.sem_num = i;
-       sb.sem_op = -1;
-       sb.sem_flg = SEM_UNDO;
 
-       if (semop(sem_id, &sb, 1) != 0) {
-               DEBUG(0,("ERROR: IPC lock failed on semaphore %d\n", i));
-               return False;
+#ifdef SECURE_SEMAPHORES
+       if (current_user.uid != 0) {
+               become_root(0);
+               became_root = 1;
        }
-
-       return True;
-}
-
-static BOOL sem_unlock(int i)
-{
-       struct sembuf sb;
-       if (read_only) return True;
+#endif
 
        sb.sem_num = i;
-       sb.sem_op = 1;
+       sb.sem_op = op;
        sb.sem_flg = SEM_UNDO;
 
-       if (semop(sem_id, &sb, 1) != 0) {
-               DEBUG(0,("ERROR: IPC unlock failed on semaphore %d\n", i));
-               return False;
+       ret = semop(sem_id, &sb, 1);
+
+       if (ret != 0) {
+               DEBUG(0,("ERROR: sem_change(%d,%d) failed (%s)\n", 
+                        i, op, strerror(errno)));
        }
 
-       return True;
+#ifdef SECURE_SEMAPHORES
+       if (became_root) {
+               unbecome_root(0);
+       }
+#endif
+
+       return ret == 0;
 }
 
 static BOOL global_lock(void)
 {
        global_lock_count++;
        if (global_lock_count == 1)
-               return sem_lock(0);
+               return sem_change(0, -1);
        return True;
 }
 
@@ -138,7 +150,7 @@ static BOOL global_unlock(void)
 {
        global_lock_count--;
        if (global_lock_count == 0)
-               return sem_unlock(0);
+               return sem_change(0, 1);
        return True;
 }
 
@@ -461,8 +473,7 @@ static int shm_get_userdef_off(void)
   ******************************************************************/
 static BOOL shm_lock_hash_entry(unsigned int entry)
 {
-       DEBUG(0,("hash lock %d\n", entry));
-       return sem_lock(entry+1);
+       return sem_change(entry+1, -1);
 }
 
 /*******************************************************************
@@ -470,8 +481,7 @@ static BOOL shm_lock_hash_entry(unsigned int entry)
   ******************************************************************/
 static BOOL shm_unlock_hash_entry(unsigned int entry)
 {
-       DEBUG(0,("hash unlock %d\n", entry));
-       return sem_unlock(entry+1);
+       return sem_change(entry+1, 1);
 }
 
 
@@ -545,7 +555,7 @@ struct shmem_ops *sysv_shm_open(int ronly)
 
                while (hash_size > 1) {
                        sem_id = semget(SEMAPHORE_KEY, hash_size+1, 
-                                       IPC_CREAT | IPC_EXCL | IPC_PERMS);
+                                       IPC_CREAT|IPC_EXCL| SEMAPHORE_PERMS);
                        if (sem_id != -1 || errno != EINVAL) break;
                        hash_size--;
                }
@@ -584,6 +594,11 @@ struct shmem_ops *sysv_shm_open(int ronly)
                        DEBUG(0,("ERROR: root did not create the semaphore\n"));
                        return NULL;
                }
+
+               sem_ds.sem_perm.mode = SEMAPHORE_PERMS;
+               if (semctl(sem_id, 0, IPC_SET, su) != 0) {
+                       DEBUG(0,("ERROR shm_open : can't IPC_SET\n"));
+               }
        }
 
        

diff --git a/source/utils/status.c b/source/utils/status.c
index f124d79939cae4da8c9cb55da4fc9d6756defe83..1a05f2b1afe573ce266b863961ef51be6276af73 100644 (file)
--- a/source/utils/status.c
+++ b/source/utils/status.c
@@ -58,6 +58,7 @@ unsigned int   Ucrit_IsActive = 0;                    /* added by OH */
  void unbecome_root(BOOL restore_dir) {}
 connection_struct Connections[MAX_CONNECTIONS];
 files_struct Files[MAX_OPEN_FILES];
+struct current_user current_user;
 
 
 static void print_share_mode(share_mode_entry *e, char *fname)