[PATCH] binder: check for binder_thread allocation failure in binder_poll()

[Eric Biggers]

From: Eric Biggers <ebiggers@xxxxxxxxxx>

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@xxxxxxxxxxxxxxxx>
Fixes: 457b9a6f09f0 ("Staging: android: add binder driver")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
 drivers/android/binder.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index d21040c5d343f..326ca8ea9ebcf 100644
--- 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;
-- 
2.16.1