Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:48496 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751553AbeDMWfS (ORCPT ); Fri, 13 Apr 2018 18:35:18 -0400 Date: Fri, 13 Apr 2018 15:35:16 -0700 From: akpm@linux-foundation.org To: ying.huang@intel.com, tglx@linutronix.de, stable@vger.kernel.org, regressions@leemhuis.info, peterz@infradead.org, kirill.shutemov@linux.intel.com, corbet@lwn.net, mst@redhat.com, akpm@linux-foundation.org, mm-commits@vger.kernel.org, torvalds@linux-foundation.org Subject: [patch 02/27] mm/gup_benchmark: handle gup failures Message-ID: <20180413223516.545q4%akpm@linux-foundation.org> Sender: stable-owner@vger.kernel.org List-ID: From: "Michael S. Tsirkin" Subject: mm/gup_benchmark: handle gup failures Patch series "mm/get_user_pages_fast fixes, cleanups", v2. Turns out get_user_pages_fast and __get_user_pages_fast return different values on error when given a single page: __get_user_pages_fast returns 0. get_user_pages_fast returns either 0 or an error. Callers of get_user_pages_fast expect an error so fix it up to return an error consistently. Stress the difference between get_user_pages_fast and __get_user_pages_fast to make sure callers aren't confused. This patch (of 3): __gup_benchmark_ioctl does not handle the case where get_user_pages_fast fails: - a negative return code will cause a buffer overrun - returning with partial success will cause use of uninitialized memory. [akpm@linux-foundation.org: simplification] Link: http://lkml.kernel.org/r/1522962072-182137-3-git-send-email-mst@redhat.com Signed-off-by: Michael S. Tsirkin Reviewed-by: Andrew Morton Cc: Kirill A. Shutemov Cc: Huang Ying Cc: Jonathan Corbet Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Thorsten Leemhuis Cc: Signed-off-by: Andrew Morton --- mm/gup_benchmark.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff -puN mm/gup_benchmark.c~mm-gup_benchmark-handle-gup-failures mm/gup_benchmark.c --- a/mm/gup_benchmark.c~mm-gup_benchmark-handle-gup-failures +++ a/mm/gup_benchmark.c @@ -23,7 +23,7 @@ static int __gup_benchmark_ioctl(unsigne struct page **pages; nr_pages = gup->size / PAGE_SIZE; - pages = kvmalloc(sizeof(void *) * nr_pages, GFP_KERNEL); + pages = kvzalloc(sizeof(void *) * nr_pages, GFP_KERNEL); if (!pages) return -ENOMEM; @@ -41,6 +41,8 @@ static int __gup_benchmark_ioctl(unsigne } nr = get_user_pages_fast(addr, nr, gup->flags & 1, pages + i); + if (nr <= 0) + break; i += nr; } end_time = ktime_get(); _