binder: check for binder_thread allocation failure in binder_poll()

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 15e3d3c..ad5e662 100644 (file)
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -4391,6 +4391,8 @@ static __poll_t binder_poll(struct file *filp,
        bool wait_for_proc_work;
 
        thread = binder_get_thread(proc);
+       if (!thread)
+               return POLLERR;
 
        binder_inner_proc_lock(thread->proc);
        thread->looper |= BINDER_LOOPER_STATE_POLL;