FROMLIST: binder: protect proc->threads with inner_lock

(from https://patchwork.kernel.org/patch/9817775/)

proc->threads will need to be accessed with higher
locks of other processes held so use proc->inner_lock
to protect it. proc->tmp_ref now needs to be protected
by proc->inner_lock.

Change-Id: Id4cff2c9786d900b7846ec9b1816f7a07655c429
Signed-off-by: Todd Kjos <tkjos@google.com>

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index a68ccc5129b8b3541934759ef1eb5c758fbb8ef3..9de2594e20bb668dec827202c291e4cd5f693533 100644 (file)
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -468,6 +468,7 @@ enum binder_deferred_state {
  * struct binder_proc - binder process bookkeeping
  * @proc_node:            element for binder_procs list
  * @threads:              rbtree of binder_threads in this proc
+ *                        (protected by @inner_lock)
  * @nodes:                rbtree of binder nodes associated with
  *                        this proc ordered by node->ptr
  *                        (protected by @inner_lock)
@@ -485,6 +486,7 @@ enum binder_deferred_state {
  *                        (protected by binder_deferred_lock)
  * @is_dead:              process is dead and awaiting free
  *                        when outstanding transactions are cleaned up
+ *                        (protected by @inner_lock)
  * @todo:                 list of work for this process
  *                        (protected by @inner_lock)
  * @wait:                 wait queue head to wait for proc work
@@ -500,6 +502,7 @@ enum binder_deferred_state {
  * @requested_threads_started: number binder threads started
  * @ready_threads:        number of threads waiting for proc work
  * @tmp_ref:              temporary reference to indicate proc is in use
+ *                        (protected by @inner_lock)
  * @default_priority:     default scheduler priority
  *                        (invariant after initialized)
  * @debugfs_entry:        debugfs node
@@ -555,6 +558,7 @@ enum {
  * @proc:                 binder process for this thread
  *                        (invariant after initialization)
  * @rb_node:              element for proc->threads rbtree
+ *                        (protected by @proc->inner_lock)
  * @pid:                  PID for this thread
  *                        (invariant after initialization)
  * @looper:               bitmap of looping state
@@ -575,6 +579,7 @@ enum {
  *                        always be acquired)
  * @is_dead:              thread is dead and awaiting free
  *                        when outstanding transactions are cleaned up
+ *                        (protected by @proc->inner_lock)
  *
  * Bookkeeping structure for binder threads.
  */
@@ -1667,15 +1672,15 @@ static void binder_thread_dec_tmpref(struct binder_thread *thread)
        /*
         * atomic is used to protect the counter value while
         * it cannot reach zero or thread->is_dead is false
-        *
-        * TODO: future patch adds locking to ensure that the
-        * check of tmp_ref and is_dead is done with a lock held
         */
+       binder_inner_proc_lock(thread->proc);
        atomic_dec(&thread->tmp_ref);
        if (thread->is_dead && !atomic_read(&thread->tmp_ref)) {
+               binder_inner_proc_unlock(thread->proc);
                binder_free_thread(thread);
                return;
        }
+       binder_inner_proc_unlock(thread->proc);
 }
 
 /**
@@ -1692,12 +1697,15 @@ static void binder_thread_dec_tmpref(struct binder_thread *thread)
  */
 static void binder_proc_dec_tmpref(struct binder_proc *proc)
 {
+       binder_inner_proc_lock(proc);
        proc->tmp_ref--;
        if (proc->is_dead && RB_EMPTY_ROOT(&proc->threads) &&
                        !proc->tmp_ref) {
+               binder_inner_proc_unlock(proc);
                binder_free_proc(proc);
                return;
        }
+       binder_inner_proc_unlock(proc);
 }
 
 /**
@@ -2480,7 +2488,9 @@ static void binder_transaction(struct binder_proc *proc,
                        return_error_line = __LINE__;
                        goto err_dead_binder;
                }
+               binder_inner_proc_lock(target_proc);
                target_proc->tmp_ref++;
+               binder_inner_proc_unlock(target_proc);
                binder_node_unlock(target_node);
                if (security_binder_transaction(proc->tsk,
                                                target_proc->tsk) < 0) {
@@ -3854,7 +3864,8 @@ static void binder_release_work(struct binder_proc *proc,
 
 }
 
-static struct binder_thread *binder_get_thread(struct binder_proc *proc)
+static struct binder_thread *binder_get_thread_ilocked(
+               struct binder_proc *proc, struct binder_thread *new_thread)
 {
        struct binder_thread *thread = NULL;
        struct rb_node *parent = NULL;
@@ -3869,25 +3880,45 @@ static struct binder_thread *binder_get_thread(struct binder_proc *proc)
                else if (current->pid > thread->pid)
                        p = &(*p)->rb_right;
                else
-                       break;
+                       return thread;
        }
-       if (*p == NULL) {
-               thread = kzalloc(sizeof(*thread), GFP_KERNEL);
-               if (thread == NULL)
+       if (!new_thread)
+               return NULL;
+       thread = new_thread;
+       binder_stats_created(BINDER_STAT_THREAD);
+       thread->proc = proc;
+       thread->pid = current->pid;
+       atomic_set(&thread->tmp_ref, 0);
+       init_waitqueue_head(&thread->wait);
+       INIT_LIST_HEAD(&thread->todo);
+       rb_link_node(&thread->rb_node, parent, p);
+       rb_insert_color(&thread->rb_node, &proc->threads);
+       thread->looper_need_return = true;
+       thread->return_error.work.type = BINDER_WORK_RETURN_ERROR;
+       thread->return_error.cmd = BR_OK;
+       thread->reply_error.work.type = BINDER_WORK_RETURN_ERROR;
+       thread->reply_error.cmd = BR_OK;
+
+       return thread;
+}
+
+static struct binder_thread *binder_get_thread(struct binder_proc *proc)
+{
+       struct binder_thread *thread;
+       struct binder_thread *new_thread;
+
+       binder_inner_proc_lock(proc);
+       thread = binder_get_thread_ilocked(proc, NULL);
+       binder_inner_proc_unlock(proc);
+       if (!thread) {
+               new_thread = kzalloc(sizeof(*thread), GFP_KERNEL);
+               if (new_thread == NULL)
                        return NULL;
-               binder_stats_created(BINDER_STAT_THREAD);
-               thread->proc = proc;
-               thread->pid = current->pid;
-               atomic_set(&thread->tmp_ref, 0);
-               init_waitqueue_head(&thread->wait);
-               INIT_LIST_HEAD(&thread->todo);
-               rb_link_node(&thread->rb_node, parent, p);
-               rb_insert_color(&thread->rb_node, &proc->threads);
-               thread->looper_need_return = true;
-               thread->return_error.work.type = BINDER_WORK_RETURN_ERROR;
-               thread->return_error.cmd = BR_OK;
-               thread->reply_error.work.type = BINDER_WORK_RETURN_ERROR;
-               thread->reply_error.cmd = BR_OK;
+               binder_inner_proc_lock(proc);
+               thread = binder_get_thread_ilocked(proc, new_thread);
+               binder_inner_proc_unlock(proc);
+               if (thread != new_thread)
+                       kfree(new_thread);
        }
        return thread;
 }
@@ -3918,6 +3949,7 @@ static int binder_thread_release(struct binder_proc *proc,
        int active_transactions = 0;
        struct binder_transaction *last_t = NULL;
 
+       binder_inner_proc_lock(thread->proc);
        /*
         * take a ref on the proc so it survives
         * after we remove this thread from proc->threads.
@@ -3965,6 +3997,7 @@ static int binder_thread_release(struct binder_proc *proc,
                if (t)
                        spin_lock(&t->lock);
        }
+       binder_inner_proc_unlock(thread->proc);
 
        if (send_reply)
                binder_send_failed_reply(send_reply, BR_DEAD_REPLY);
@@ -4338,6 +4371,7 @@ static void binder_deferred_flush(struct binder_proc *proc)
        struct rb_node *n;
        int wake_count = 0;
 
+       binder_inner_proc_lock(proc);
        for (n = rb_first(&proc->threads); n != NULL; n = rb_next(n)) {
                struct binder_thread *thread = rb_entry(n, struct binder_thread, rb_node);
 
@@ -4347,6 +4381,7 @@ static void binder_deferred_flush(struct binder_proc *proc)
                        wake_count++;
                }
        }
+       binder_inner_proc_unlock(proc);
        wake_up_interruptible_all(&proc->wait);
 
        binder_debug(BINDER_DEBUG_OPEN_CLOSE,
@@ -4445,6 +4480,7 @@ static void binder_deferred_release(struct binder_proc *proc)
                context->binder_context_mgr_node = NULL;
        }
        mutex_unlock(&context->context_mgr_node_lock);
+       binder_inner_proc_lock(proc);
        /*
         * Make sure proc stays alive after we
         * remove all the threads
@@ -4458,13 +4494,14 @@ static void binder_deferred_release(struct binder_proc *proc)
                struct binder_thread *thread;
 
                thread = rb_entry(n, struct binder_thread, rb_node);
+               binder_inner_proc_unlock(proc);
                threads++;
                active_transactions += binder_thread_release(proc, thread);
+               binder_inner_proc_lock(proc);
        }
 
        nodes = 0;
        incoming_refs = 0;
-       binder_inner_proc_lock(proc);
        while ((n = rb_first(&proc->nodes))) {
                struct binder_node *node;
 
@@ -4872,10 +4909,13 @@ static void print_binder_proc_stats(struct seq_file *m,
        struct binder_work *w;
        struct rb_node *n;
        int count, strong, weak;
+       size_t free_async_space =
+               binder_alloc_get_free_async_space(&proc->alloc);
 
        seq_printf(m, "proc %d\n", proc->pid);
        seq_printf(m, "context %s\n", proc->context->name);
        count = 0;
+       binder_inner_proc_lock(proc);
        for (n = rb_first(&proc->threads); n != NULL; n = rb_next(n))
                count++;
        seq_printf(m, "  threads: %d\n", count);
@@ -4884,9 +4924,8 @@ static void print_binder_proc_stats(struct seq_file *m,
                        "  free async space %zd\n", proc->requested_threads,
                        proc->requested_threads_started, proc->max_threads,
                        proc->ready_threads,
-                       binder_alloc_get_free_async_space(&proc->alloc));
+                       free_async_space);
        count = 0;
-       binder_inner_proc_lock(proc);
        for (n = rb_first(&proc->nodes); n != NULL; n = rb_next(n))
                count++;
        binder_inner_proc_unlock(proc);