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Subject[PATCH 34/37] binder: protect binder_ref with outer lock
Date
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.

Signed-off-by: Todd Kjos <tkjos@google.com>
---
drivers/android/binder.c | 133 +++++++++++++++++++++++++++++------------------
1 file changed, 83 insertions(+), 50 deletions(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 704540ea3e12..f07f0d488aa4 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -475,7 +475,9 @@ 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);
--
2.13.2.725.g09c95d1e9-goog
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