linux-kernel - [PATCH] android: binder: check result of binder_get_thread() in binder

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Date:   Mon, 8 May 2017 13:43:23 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Arve Hjønnevåg <arve@...roid.com>,
        Riley Andrews <riandrews@...roid.com>,
        Martijn Coenen <maco@...gle.com>,
        John Stultz <john.stultz@...aro.org>,
        Douglas Anderson <dianders@...omium.org>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: [PATCH] android: binder: check result of binder_get_thread() in
 binder_poll()

If binder_get_thread() fails to give us a thread data, we should avoid
dereferencing a NULL pointer and return POLLERR instead.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
---
 drivers/android/binder.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index aae4d8d4be36..66ed714fedd5 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -3103,18 +3103,22 @@ static unsigned int binder_poll(struct file *filp,
 				struct poll_table_struct *wait)
 {
 	struct binder_proc *proc = filp->private_data;
-	struct binder_thread *thread = NULL;
+	struct binder_thread *thread;
 	int wait_for_proc_work;
 
 	binder_lock(__func__);
 
 	thread = binder_get_thread(proc);
-
-	wait_for_proc_work = thread->transaction_stack == NULL &&
-		list_empty(&thread->todo) && thread->return_error == BR_OK;
+	if (thread)
+		wait_for_proc_work = thread->transaction_stack == NULL &&
+				     list_empty(&thread->todo) &&
+				     thread->return_error == BR_OK;
 
 	binder_unlock(__func__);
 
+	if (!thread)
+		return POLLERR;
+
 	if (wait_for_proc_work) {
 		if (binder_has_proc_work(proc, thread))
 			return POLLIN;
-- 
2.13.0.rc1.294.g07d810a77f-goog


-- 
Dmitry