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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, syzbot <syzkaller@googlegroups.com>,
        Eric Biggers <ebiggers@google.com>
Subject: [PATCH 4.9 038/145] binder: check for binder_thread allocation failure in binder_poll()
Date:   Fri, 23 Feb 2018 19:25:44 +0100
Message-Id: <20180223170729.872536682@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Biggers <ebiggers@google.com>

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>

---
 drivers/android/binder.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -2628,6 +2628,8 @@ static unsigned int binder_poll(struct f
 	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;