linux-kernel - [PATCH 5.1 125/138] binder: fix memory leak in error path

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Date:   Fri, 12 Jul 2019 14:19:49 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+182ce46596c3f2e1eb24@...kaller.appspotmail.com,
        Todd Kjos <tkjos@...gle.com>
Subject: [PATCH 5.1 125/138] binder: fix memory leak in error path

From: Todd Kjos <tkjos@...roid.com>

commit 1909a671dbc3606685b1daf8b22a16f65ea7edda upstream.

syzkallar found a 32-byte memory leak in a rarely executed error
case. The transaction complete work item was not freed if put_user()
failed when writing the BR_TRANSACTION_COMPLETE to the user command
buffer. Fixed by freeing it before put_user() is called.

Reported-by: syzbot+182ce46596c3f2e1eb24@...kaller.appspotmail.com
Signed-off-by: Todd Kjos <tkjos@...gle.com>
Cc: stable <stable@...r.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/android/binder.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -4267,6 +4267,8 @@ retry:
 		case BINDER_WORK_TRANSACTION_COMPLETE: {
 			binder_inner_proc_unlock(proc);
 			cmd = BR_TRANSACTION_COMPLETE;
+			kfree(w);
+			binder_stats_deleted(BINDER_STAT_TRANSACTION_COMPLETE);
 			if (put_user(cmd, (uint32_t __user *)ptr))
 				return -EFAULT;
 			ptr += sizeof(uint32_t);
@@ -4275,8 +4277,6 @@ retry:
 			binder_debug(BINDER_DEBUG_TRANSACTION_COMPLETE,
 				     "%d:%d BR_TRANSACTION_COMPLETE\n",
 				     proc->pid, thread->pid);
-			kfree(w);
-			binder_stats_deleted(BINDER_STAT_TRANSACTION_COMPLETE);
 		} break;
 		case BINDER_WORK_NODE: {
 			struct binder_node *node = container_of(w, struct binder_node, work);