From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f70.google.com (mail-wm0-f70.google.com [74.125.82.70]) by kanga.kvack.org (Postfix) with ESMTP id DC0DF6B1E78 for ; Tue, 21 Aug 2018 07:36:38 -0400 (EDT) Received: by mail-wm0-f70.google.com with SMTP id m129-v6so2072948wma.8 for ; Tue, 21 Aug 2018 04:36:38 -0700 (PDT) Received: from youngberry.canonical.com (youngberry.canonical.com. [91.189.89.112]) by mx.google.com with ESMTPS id x17-v6si7819028wrv.92.2018.08.21.04.36.37 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 21 Aug 2018 04:36:37 -0700 (PDT) From: Colin King Subject: [PATCH] mm/gup_benchmark: fix unsigned comparison with less than zero Date: Tue, 21 Aug 2018 12:36:34 +0100 Message-Id: <20180821113634.3782-1-colin.king@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton , "Kirill A . Shutemov" , "Michael S . Tsirkin" , linux-mm@kvack.org Cc: kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org From: Colin Ian King Currently the return from get_user_pages_fast is being checked to be less than zero for an error check, however, the variable being checked is unsigned so the check is always false. Fix this by using a signed long instead. Detected by Coccinelle ("Unsigned expression compared with zero: nr <= 0") Fixes: 64c349f4ae78 ("mm: add infrastructure for get_user_pages_fast() benchmarking") Signed-off-by: Colin Ian King --- mm/gup_benchmark.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/mm/gup_benchmark.c b/mm/gup_benchmark.c index 6a473709e9b6..a9a15e7a1185 100644 --- a/mm/gup_benchmark.c +++ b/mm/gup_benchmark.c @@ -31,6 +31,8 @@ static int __gup_benchmark_ioctl(unsigned int cmd, nr = gup->nr_pages_per_call; start_time = ktime_get(); for (addr = gup->addr; addr < gup->addr + gup->size; addr = next) { + long n; + if (nr != gup->nr_pages_per_call) break; @@ -40,10 +42,10 @@ static int __gup_benchmark_ioctl(unsigned int cmd, nr = (next - addr) / PAGE_SIZE; } - nr = get_user_pages_fast(addr, nr, gup->flags & 1, pages + i); - if (nr <= 0) + n = get_user_pages_fast(addr, nr, gup->flags & 1, pages + i); + if (n <= 0) break; - i += nr; + i += n; } end_time = ktime_get(); -- 2.17.1