linux-kernel - [PATCH] futex: Prevent overflow by strengthen input validation

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Message-ID: <1513242294-31786-1-git-send-email-lijinyue@huawei.com>
Date:   Thu, 14 Dec 2017 17:04:54 +0800
From:   Li Jinyue <lijinyue@...wei.com>
To:     <tglx@...utronix.de>, <mingo@...hat.com>, <peterz@...radead.org>,
        <dvhart@...radead.org>
CC:     <linux-kernel@...r.kernel.org>, Li Jinyue <lijinyue@...wei.com>
Subject: [PATCH] futex: Prevent overflow by strengthen input validation

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

To prevent overflow, we don't allow nr_wake and nr_requeue to accept
a negative entropy value.

Signed-off-by: Li Jinyue <lijinyue@...wei.com>
---
 kernel/futex.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index 57d0b36..0abfa09 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1878,6 +1878,9 @@ static int futex_requeue(u32 __user *uaddr1, unsigned int flags,
 	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
-- 
1.6.0.2