linux-kernel - [PATCH 2/2] vhost: Fix the calculation in vhost

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Date:   Fri, 16 Jul 2021 18:22:39 +0800
From:   Xie Yongji <xieyongji@...edance.com>
To:     mst@...hat.com, jasowang@...hat.com, dan.carpenter@...cle.com
Cc:     virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] vhost: Fix the calculation in vhost_overflow()

This fixes the incorrect calculation for integer overflow
when the last address of iova range is 0xffffffff.

Fixes: ec33d031a14b ("vhost: detect 32 bit integer wrap around“)
Reported-by: Jason Wang <jasowang@...hat.com>
Signed-off-by: Xie Yongji <xieyongji@...edance.com>
---
 drivers/vhost/vhost.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index b9e853e6094d..a9fd1b311d2f 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -738,7 +738,8 @@ static bool log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
 static bool vhost_overflow(u64 uaddr, u64 size)
 {
 	/* Make sure 64 bit math will not overflow. */
-	return uaddr > ULONG_MAX || size > ULONG_MAX || uaddr > ULONG_MAX - size;
+	return uaddr > ULONG_MAX || size > ULONG_MAX ||
+	       uaddr - 1 > ULONG_MAX - size;
 }
 
 /* Caller should have vq mutex and device mutex. */
-- 
2.11.0