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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, Li Jinyue <lijinyue@huawei.com>,
        Thomas Gleixner <tglx@linutronix.de>, peterz@infradead.org,
        dvhart@infradead.org
Subject: [PATCH 4.14 17/89] futex: Prevent overflow by strengthen input validation
Date:   Mon, 22 Jan 2018 09:44:57 +0100
Message-Id: <20180122083956.427607580@linuxfoundation.org>
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4.14-stable review patch.  If anyone has any objections, please let me know.

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

From: Li Jinyue <lijinyue@huawei.com>

commit fbe0e839d1e22d88810f3ee3e2f1479be4c0aa4a upstream.

UBSAN reports signed integer overflow in kernel/futex.c:

 UBSAN: Undefined behaviour in kernel/futex.c:2041:18
 signed integer overflow:
 0 - -2147483648 cannot be represented in type 'int'

Add a sanity check to catch negative values of nr_wake and nr_requeue.

Signed-off-by: Li Jinyue <lijinyue@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: peterz@infradead.org
Cc: dvhart@infradead.org
Link: https://lkml.kernel.org/r/1513242294-31786-1-git-send-email-lijinyue@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 kernel/futex.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1878,6 +1878,9 @@ static int futex_requeue(u32 __user *uad
 	struct futex_q *this, *next;
 	DEFINE_WAKE_Q(wake_q);
 
+	if (nr_wake < 0 || nr_requeue < 0)
+		return -EINVAL;
+
 	/*
 	 * When PI not supported: return -ENOSYS if requeue_pi is true,
 	 * consequently the compiler knows requeue_pi is always false past