linux-kernel - [PATCH] binder: check for binder_thread allocation failure in binder

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Date:   Tue, 30 Jan 2018 23:11:24 -0800
From:   Eric Biggers <ebiggers3@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arve Hjønnevåg <arve@...roid.com>,
        Todd Kjos <tkjos@...roid.com>,
        Martijn Coenen <maco@...roid.com>
Cc:     devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com, Eric Biggers <ebiggers@...gle.com>
Subject: [PATCH] binder: check for binder_thread allocation failure in binder_poll()

From: Eric Biggers <ebiggers@...gle.com>

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@...glegroups.com>
Fixes: 457b9a6f09f0 ("Staging: android: add binder driver")
Cc: stable@...r.kernel.org
Signed-off-by: Eric Biggers <ebiggers@...gle.com>
---
 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