binder: check for binder_thread allocation failure in binder_poll()

commit f88982679f54f75daa5b8eff3da72508f1e7422f upstream.

If the kzalloc() in binder_get_thread() fails, binder_poll()
dereferences the resulting NULL pointer.

Fix it by returning POLLERR if the memory allocation failed.

This bug was found by syzkaller using fault injection.

Reported-by: syzbot <syzkaller@googlegroups.com>
Fixes: 457b9a6f09f0 ("Staging: android: add binder driver")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 15009b2b33c7beafe9dc3063b2d560c10a04b4e7..3b6ac80b21272749ddf9d4365e45f2ac5f111158 100644 (file)
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -2628,6 +2628,8 @@ static unsigned int binder_poll(struct file *filp,
        binder_lock(__func__);
 
        thread = binder_get_thread(proc);
+       if (!thread)
+               return POLLERR;
 
        wait_for_proc_work = thread->transaction_stack == NULL &&
                list_empty(&thread->todo) && thread->return_error == BR_OK;