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From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org, "Thomas Gleixner" <tglx@linutronix.de>,
        peterz@infradead.org, "Li Jinyue" <lijinyue@huawei.com>,
        dvhart@infradead.org
Date:   Wed, 28 Feb 2018 15:20:18 +0000
Message-ID: <lsq.1519831218.39324522@decadent.org.uk>
Subject: [PATCH 3.16 204/254] futex: Prevent overflow by strengthen input
 validation
In-Reply-To: <lsq.1519831217.271785318@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

3.16.55-rc1 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
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 kernel/futex.c | 3 +++
 1 file changed, 3 insertions(+)

--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1531,6 +1531,9 @@ static int futex_requeue(u32 __user *uad
 	struct futex_hash_bucket *hb1, *hb2;
 	struct futex_q *this, *next;
 
+	if (nr_wake < 0 || nr_requeue < 0)
+		return -EINVAL;
+
 	if (requeue_pi) {
 		/*
 		 * Requeue PI only works on two distinct uaddrs. This