FROMLIST: binder: protect binder_ref with outer lock

(from https://patchwork.kernel.org/patch/9817771/)

Use proc->outer_lock to protect the binder_ref structure.
The outer lock allows functions operating on the binder_ref
to do nested acquires of node and inner locks as necessary
to attach refs to nodes atomically.

Binder refs must never be accesssed without holding the
outer lock.

Change-Id: Iffb9ae47fd383b87b70ee6bec344cde9f8d24996
Signed-off-by: Todd Kjos <tkjos@google.com>

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 50831c7dba55ba3e70cb66ae273cbe49aef6f658..29ae9174662ca3ba8d3665529d9f34245062725b 100644 (file)
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -474,7 +474,9 @@ enum binder_deferred_state {
  *                        this proc ordered by node->ptr
  *                        (protected by @inner_lock)
  * @refs_by_desc:         rbtree of refs ordered by ref->desc
+ *                        (protected by @outer_lock)
  * @refs_by_node:         rbtree of refs ordered by ref->node
+ *                        (protected by @outer_lock)
  * @pid                   PID of group_leader of process
  *                        (invariant after initialized)
  * @tsk                   task_struct for group_leader of process
@@ -1269,8 +1271,8 @@ static void binder_put_node(struct binder_node *node)
        binder_dec_node_tmpref(node);
 }
 
-static struct binder_ref *binder_get_ref(struct binder_proc *proc,
-                                        u32 desc, bool need_strong_ref)
+static struct binder_ref *binder_get_ref_olocked(struct binder_proc *proc,
+                                                u32 desc, bool need_strong_ref)
 {
        struct rb_node *n = proc->refs_by_desc.rb_node;
        struct binder_ref *ref;
@@ -1293,7 +1295,7 @@ static struct binder_ref *binder_get_ref(struct binder_proc *proc,
 }
 
 /**
- * binder_get_ref_for_node() - get the ref associated with given node
+ * binder_get_ref_for_node_olocked() - get the ref associated with given node
  * @proc:      binder_proc that owns the ref
  * @node:      binder_node of target
  * @new_ref:   newly allocated binder_ref to be initialized or %NULL
@@ -1310,9 +1312,10 @@ static struct binder_ref *binder_get_ref(struct binder_proc *proc,
  *             new_ref. new_ref must be kfree'd by the caller in
  *             this case.
  */
-static struct binder_ref *binder_get_ref_for_node(struct binder_proc *proc,
-                                                 struct binder_node *node,
-                                                 struct binder_ref *new_ref)
+static struct binder_ref *binder_get_ref_for_node_olocked(
+                                       struct binder_proc *proc,
+                                       struct binder_node *node,
+                                       struct binder_ref *new_ref)
 {
        struct binder_context *context = proc->context;
        struct rb_node **p = &proc->refs_by_node.rb_node;
@@ -1375,7 +1378,7 @@ static struct binder_ref *binder_get_ref_for_node(struct binder_proc *proc,
        return new_ref;
 }
 
-static void binder_cleanup_ref(struct binder_ref *ref)
+static void binder_cleanup_ref_olocked(struct binder_ref *ref)
 {
        bool delete_node = false;
 
@@ -1418,17 +1421,17 @@ static void binder_cleanup_ref(struct binder_ref *ref)
 }
 
 /**
- * binder_inc_ref() - increment the ref for given handle
+ * binder_inc_ref_olocked() - increment the ref for given handle
  * @ref:         ref to be incremented
  * @strong:      if true, strong increment, else weak
  * @target_list: list to queue node work on
  *
- * Increment the ref.
+ * Increment the ref. @ref->proc->outer_lock must be held on entry
  *
  * Return: 0, if successful, else errno
  */
-static int binder_inc_ref(struct binder_ref *ref, int strong,
-                         struct list_head *target_list)
+static int binder_inc_ref_olocked(struct binder_ref *ref, int strong,
+                                 struct list_head *target_list)
 {
        int ret;
 
@@ -1457,12 +1460,9 @@ static int binder_inc_ref(struct binder_ref *ref, int strong,
  *
  * Decrement the ref.
  *
- * TODO: kfree is avoided here since an upcoming patch
- * will put this under a lock.
- *
  * Return: true if ref is cleaned up and ready to be freed
  */
-static bool binder_dec_ref(struct binder_ref *ref, int strong)
+static bool binder_dec_ref_olocked(struct binder_ref *ref, int strong)
 {
        if (strong) {
                if (ref->data.strong == 0) {
@@ -1486,13 +1486,7 @@ static bool binder_dec_ref(struct binder_ref *ref, int strong)
                ref->data.weak--;
        }
        if (ref->data.strong == 0 && ref->data.weak == 0) {
-               binder_cleanup_ref(ref);
-               /*
-                * TODO: we could kfree(ref) here, but an upcoming
-                * patch will call this with a lock held, so we
-                * return an indication that the ref should be
-                * freed.
-                */
+               binder_cleanup_ref_olocked(ref);
                return true;
        }
        return false;
@@ -1517,7 +1511,8 @@ static struct binder_node *binder_get_node_from_ref(
        struct binder_node *node;
        struct binder_ref *ref;
 
-       ref = binder_get_ref(proc, desc, need_strong_ref);
+       binder_proc_lock(proc);
+       ref = binder_get_ref_olocked(proc, desc, need_strong_ref);
        if (!ref)
                goto err_no_ref;
        node = ref->node;
@@ -1528,10 +1523,12 @@ static struct binder_node *binder_get_node_from_ref(
        binder_inc_node_tmpref(node);
        if (rdata)
                *rdata = ref->data;
+       binder_proc_unlock(proc);
 
        return node;
 
 err_no_ref:
+       binder_proc_unlock(proc);
        return NULL;
 }
 
@@ -1571,24 +1568,27 @@ static int binder_update_ref_for_handle(struct binder_proc *proc,
        struct binder_ref *ref;
        bool delete_ref = false;
 
-       ref = binder_get_ref(proc, desc, strong);
+       binder_proc_lock(proc);
+       ref = binder_get_ref_olocked(proc, desc, strong);
        if (!ref) {
                ret = -EINVAL;
                goto err_no_ref;
        }
        if (increment)
-               ret = binder_inc_ref(ref, strong, NULL);
+               ret = binder_inc_ref_olocked(ref, strong, NULL);
        else
-               delete_ref = binder_dec_ref(ref, strong);
+               delete_ref = binder_dec_ref_olocked(ref, strong);
 
        if (rdata)
                *rdata = ref->data;
+       binder_proc_unlock(proc);
 
        if (delete_ref)
                binder_free_ref(ref);
        return ret;
 
 err_no_ref:
+       binder_proc_unlock(proc);
        return ret;
 }
 
@@ -1633,15 +1633,19 @@ static int binder_inc_ref_for_node(struct binder_proc *proc,
        struct binder_ref *new_ref = NULL;
        int ret = 0;
 
-       ref = binder_get_ref_for_node(proc, node, NULL);
+       binder_proc_lock(proc);
+       ref = binder_get_ref_for_node_olocked(proc, node, NULL);
        if (!ref) {
+               binder_proc_unlock(proc);
                new_ref = kzalloc(sizeof(*ref), GFP_KERNEL);
                if (!new_ref)
                        return -ENOMEM;
-               ref = binder_get_ref_for_node(proc, node, new_ref);
+               binder_proc_lock(proc);
+               ref = binder_get_ref_for_node_olocked(proc, node, new_ref);
        }
-       ret = binder_inc_ref(ref, strong, target_list);
+       ret = binder_inc_ref_olocked(ref, strong, target_list);
        *rdata = ref->data;
+       binder_proc_unlock(proc);
        if (new_ref && ref != new_ref)
                /*
                 * Another thread created the ref first so
@@ -2497,11 +2501,14 @@ static void binder_transaction(struct binder_proc *proc,
                         * stays alive until the transaction is
                         * done.
                         */
-                       ref = binder_get_ref(proc, tr->target.handle, true);
+                       binder_proc_lock(proc);
+                       ref = binder_get_ref_olocked(proc, tr->target.handle,
+                                                    true);
                        if (ref) {
                                binder_inc_node(ref->node, 1, 0, NULL);
                                target_node = ref->node;
                        }
+                       binder_proc_unlock(proc);
                        if (target_node == NULL) {
                                binder_user_error("%d:%d got transaction to invalid handle\n",
                                        proc->pid, thread->pid);
@@ -3277,7 +3284,7 @@ static int binder_thread_write(struct binder_proc *proc,
                        uint32_t target;
                        binder_uintptr_t cookie;
                        struct binder_ref *ref;
-                       struct binder_ref_death *death;
+                       struct binder_ref_death *death = NULL;
 
                        if (get_user(target, (uint32_t __user *)ptr))
                                return -EFAULT;
@@ -3285,7 +3292,29 @@ static int binder_thread_write(struct binder_proc *proc,
                        if (get_user(cookie, (binder_uintptr_t __user *)ptr))
                                return -EFAULT;
                        ptr += sizeof(binder_uintptr_t);
-                       ref = binder_get_ref(proc, target, false);
+                       if (cmd == BC_REQUEST_DEATH_NOTIFICATION) {
+                               /*
+                                * Allocate memory for death notification
+                                * before taking lock
+                                */
+                               death = kzalloc(sizeof(*death), GFP_KERNEL);
+                               if (death == NULL) {
+                                       WARN_ON(thread->return_error.cmd !=
+                                               BR_OK);
+                                       thread->return_error.cmd = BR_ERROR;
+                                       binder_enqueue_work(
+                                               thread->proc,
+                                               &thread->return_error.work,
+                                               &thread->todo);
+                                       binder_debug(
+                                               BINDER_DEBUG_FAILED_TRANSACTION,
+                                               "%d:%d BC_REQUEST_DEATH_NOTIFICATION failed\n",
+                                               proc->pid, thread->pid);
+                                       break;
+                               }
+                       }
+                       binder_proc_lock(proc);
+                       ref = binder_get_ref_olocked(proc, target, false);
                        if (ref == NULL) {
                                binder_user_error("%d:%d %s invalid ref %d\n",
                                        proc->pid, thread->pid,
@@ -3293,6 +3322,8 @@ static int binder_thread_write(struct binder_proc *proc,
                                        "BC_REQUEST_DEATH_NOTIFICATION" :
                                        "BC_CLEAR_DEATH_NOTIFICATION",
                                        target);
+                               binder_proc_unlock(proc);
+                               kfree(death);
                                break;
                        }
 
@@ -3310,20 +3341,8 @@ static int binder_thread_write(struct binder_proc *proc,
                                if (ref->death) {
                                        binder_user_error("%d:%d BC_REQUEST_DEATH_NOTIFICATION death notification already set\n",
                                                proc->pid, thread->pid);
-                                       break;
-                               }
-                               death = kzalloc(sizeof(*death), GFP_KERNEL);
-                               if (death == NULL) {
-                                       WARN_ON(thread->return_error.cmd !=
-                                               BR_OK);
-                                       thread->return_error.cmd = BR_ERROR;
-                                       binder_enqueue_work(
-                                               thread->proc,
-                                               &thread->return_error.work,
-                                               &thread->todo);
-                                       binder_debug(BINDER_DEBUG_FAILED_TRANSACTION,
-                                                    "%d:%d BC_REQUEST_DEATH_NOTIFICATION failed\n",
-                                                    proc->pid, thread->pid);
+                                       binder_proc_unlock(proc);
+                                       kfree(death);
                                        break;
                                }
                                binder_stats_created(BINDER_STAT_DEATH);
@@ -3356,6 +3375,7 @@ static int binder_thread_write(struct binder_proc *proc,
                                        binder_user_error("%d:%d BC_CLEAR_DEATH_NOTIFICATION death notification not active\n",
                                                proc->pid, thread->pid);
                                        binder_node_unlock(ref->node);
+                                       binder_proc_unlock(proc);
                                        break;
                                }
                                death = ref->death;
@@ -3365,6 +3385,7 @@ static int binder_thread_write(struct binder_proc *proc,
                                                (u64)death->cookie,
                                                (u64)cookie);
                                        binder_node_unlock(ref->node);
+                                       binder_proc_unlock(proc);
                                        break;
                                }
                                ref->death = NULL;
@@ -3391,6 +3412,7 @@ static int binder_thread_write(struct binder_proc *proc,
                                binder_inner_proc_unlock(proc);
                                binder_node_unlock(ref->node);
                        }
+                       binder_proc_unlock(proc);
                } break;
                case BC_DEAD_BINDER_DONE: {
                        struct binder_work *w;
@@ -4601,14 +4623,18 @@ static void binder_deferred_release(struct binder_proc *proc)
        binder_inner_proc_unlock(proc);
 
        outgoing_refs = 0;
+       binder_proc_lock(proc);
        while ((n = rb_first(&proc->refs_by_desc))) {
                struct binder_ref *ref;
 
                ref = rb_entry(n, struct binder_ref, rb_node_desc);
                outgoing_refs++;
-               binder_cleanup_ref(ref);
+               binder_cleanup_ref_olocked(ref);
+               binder_proc_unlock(proc);
                binder_free_ref(ref);
+               binder_proc_lock(proc);
        }
+       binder_proc_unlock(proc);
 
        binder_release_work(proc, &proc->todo);
        binder_release_work(proc, &proc->delivered_death);
@@ -4816,8 +4842,10 @@ static void print_binder_node_nilocked(struct seq_file *m,
        }
 }
 
-static void print_binder_ref(struct seq_file *m, struct binder_ref *ref)
+static void print_binder_ref_olocked(struct seq_file *m,
+                                    struct binder_ref *ref)
 {
+       WARN_ON(!spin_is_locked(&ref->proc->outer_lock));
        binder_node_lock(ref->node);
        seq_printf(m, "  ref %d: desc %d %snode %d s %d w %d d %pK\n",
                   ref->data.debug_id, ref->data.desc,
@@ -4869,11 +4897,14 @@ static void print_binder_proc(struct seq_file *m,
                binder_put_node(last_node);
 
        if (print_all) {
+               binder_proc_lock(proc);
                for (n = rb_first(&proc->refs_by_desc);
                     n != NULL;
                     n = rb_next(n))
-                       print_binder_ref(m, rb_entry(n, struct binder_ref,
-                                                    rb_node_desc));
+                       print_binder_ref_olocked(m, rb_entry(n,
+                                                           struct binder_ref,
+                                                           rb_node_desc));
+               binder_proc_unlock(proc);
        }
        binder_alloc_print_allocated(m, &proc->alloc);
        binder_inner_proc_lock(proc);
@@ -5013,6 +5044,7 @@ static void print_binder_proc_stats(struct seq_file *m,
        count = 0;
        strong = 0;
        weak = 0;
+       binder_proc_lock(proc);
        for (n = rb_first(&proc->refs_by_desc); n != NULL; n = rb_next(n)) {
                struct binder_ref *ref = rb_entry(n, struct binder_ref,
                                                  rb_node_desc);
@@ -5020,6 +5052,7 @@ static void print_binder_proc_stats(struct seq_file *m,
                strong += ref->data.strong;
                weak += ref->data.weak;
        }
+       binder_proc_unlock(proc);
        seq_printf(m, "  refs: %d s %d w %d\n", count, strong, weak);
 
        count = binder_alloc_get_allocated_count(&proc->alloc);