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")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.16:
 - Drop the binder global lock before returning
 - Adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/staging/android/binder.c b/drivers/staging/android/binder.c
index f83680cc115d40788ebd52b23911d9d3227257f3..f2d448ab17e230f336b484ff63a233cdc3fba962 100644 (file)
--- a/drivers/staging/android/binder.c
+++ b/drivers/staging/android/binder.c
@@ -2572,6 +2572,10 @@ static unsigned int binder_poll(struct file *filp,
        binder_lock(__func__);
 
        thread = binder_get_thread(proc);
+       if (!thread) {
+               binder_unlock(__func__);
+               return POLLERR;
+       }
 
        wait_for_proc_work = thread->transaction_stack == NULL &&
                list_empty(&thread->todo) && thread->return_error == BR_OK;