futex: Prevent overflow by strengthen input validation

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
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/1513242294-31786-1-git-send-email-lijinyue@huawei.com

diff --git a/kernel/futex.c b/kernel/futex.c
index 9e69589..8c5424d 100644 (file)
--- 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