binder: fix memory leak in error path

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@syzkaller.appspotmail.com
Signed-off-by: Todd Kjos <tkjos@google.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 748ac489ef7ebd3c68949b0b30c37a77a43878a5..8b108e9b31ccb6db8a96ac681b998b1d91d353f2 100644 (file)
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -4256,6 +4256,8 @@ static int binder_thread_read(struct binder_proc *proc,
                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);
@@ -4264,8 +4266,6 @@ static int binder_thread_read(struct binder_proc *proc,
                        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);