Fix: urcu-bp: Bulletproof RCU arena resize bug

[urcu.git] / urcu-bp.c

diff --git a/urcu-bp.c b/urcu-bp.c
index ef1e68771ab9fafe8b67da4c98672f24edd43006..93d781fcf44e5f2c9ee89928631a9d0d6cbb3e21 100644 (file)
--- a/urcu-bp.c
+++ b/urcu-bp.c
@@ -213,9 +213,9 @@ void synchronize_rcu(void)
        sigset_t newmask, oldmask;
        int ret;
 
-       ret = sigemptyset(&newmask);
+       ret = sigfillset(&newmask);
        assert(!ret);
-       ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask);
+       ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
        assert(!ret);
 
        mutex_lock(&rcu_gp_lock);
@@ -305,26 +305,37 @@ int rcu_read_ongoing(void)
  */
 static void resize_arena(struct registry_arena *arena, size_t len)
 {
-       void *new_arena;
+       void *new_p;
+       size_t old_len;
+
+       old_len = arena->len;
 
        if (!arena->p)
-               new_arena = mmap(arena->p, len,
-                                PROT_READ | PROT_WRITE,
-                                MAP_ANONYMOUS | MAP_PRIVATE,
-                                -1, 0);
+               new_p = mmap(arena->p, len,
+                       PROT_READ | PROT_WRITE,
+                       MAP_ANONYMOUS | MAP_PRIVATE,
+                       -1, 0);
        else
-               new_arena = mremap_wrapper(arena->p, arena->len,
-                                       len, MREMAP_MAYMOVE);
-       assert(new_arena != MAP_FAILED);
+               new_p = mremap_wrapper(arena->p, old_len,
+                       len, MREMAP_MAYMOVE);
+       assert(new_p != MAP_FAILED);
+
+       /*
+        * Zero the newly allocated memory. Since mmap() does not
+        * clearly specify if memory is zeroed or not (although it is
+        * very likely that it is), be extra careful by not expecting
+        * the new range to be zeroed by mremap.
+        */
+       bzero(new_p + old_len, len - old_len);
 
        /*
-        * re-used the same region ?
+        * If we did not re-use the same region, we need to update the
+        * arena pointer.
         */
-       if (new_arena == arena->p)
-               return;
+       if (new_p != arena->p)
+               arena->p = new_p;
 
-       bzero(new_arena + arena->len, len - arena->len);
-       arena->p = new_arena;
+       arena->len = len;
 }
 
 /* Called with signals off and mutex locked */
@@ -385,9 +396,9 @@ void rcu_bp_register(void)
        sigset_t newmask, oldmask;
        int ret;
 
-       ret = sigemptyset(&newmask);
+       ret = sigfillset(&newmask);
        assert(!ret);
-       ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask);
+       ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
        assert(!ret);
 
        /*
@@ -420,9 +431,9 @@ void rcu_bp_before_fork(void)
        sigset_t newmask, oldmask;
        int ret;
 
-       ret = sigemptyset(&newmask);
+       ret = sigfillset(&newmask);
        assert(!ret);
-       ret = pthread_sigmask(SIG_SETMASK, &newmask, &oldmask);
+       ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
        assert(!ret);
        mutex_lock(&rcu_gp_lock);
        saved_fork_signal_mask = oldmask;