[PATCH 31/37] binder: protect proc->threads with inner_lock

From: Todd Kjos
Date: Thu Jun 29 2017 - 15:06:12 EST

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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.

Signed-off-by: Todd Kjos <tkjos@xxxxxxxxxx>
---
drivers/android/binder.c | 87 +++++++++++++++++++++++++++++++++++-------------
1 file changed, 63 insertions(+), 24 deletions(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 4d08b5141b01..5deb9453dee4 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -469,6 +469,7 @@ 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)
@@ -486,6 +487,7 @@ 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
@@ -501,6 +503,7 @@ 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
@@ -556,6 +559,7 @@ 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
@@ -576,6 +580,7 @@ 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);
--
2.13.2.725.g09c95d1e9-goog

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