From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: [patch 052/155] mm/gup: fix omission of check on FOLL_LONGTERM in gup fast path Date: Wed, 01 Apr 2020 21:06:04 -0700 Message-ID: <20200402040604.BdOzOv4y_%akpm@linux-foundation.org> References: <20200401210155.09e3b9742e1c6e732f5a7250@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from mail.kernel.org ([198.145.29.99]:55066 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725789AbgDBEGF (ORCPT ); Thu, 2 Apr 2020 00:06:05 -0400 In-Reply-To: <20200401210155.09e3b9742e1c6e732f5a7250@linux-foundation.org> Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: akpm@linux-foundation.org, aneesh.kumar@linux.ibm.com, dan.j.williams@intel.com, hch@infradead.org, hch@lst.de, ira.weiny@intel.com, jgg@mellanox.com, jgg@ziepe.ca, jhubbard@nvidia.com, kernelfans@gmail.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, rppt@linux.ibm.com, shuah@kernel.org, torvalds@linux-foundation.org, willy@infradead.org From: Pingfan Liu Subject: mm/gup: fix omission of check on FOLL_LONGTERM in gup fast path FOLL_LONGTERM is a special case of FOLL_PIN. It suggests a pin which is going to be given to hardware and can't move. It would truncate CMA permanently and should be excluded. In gup slow path, where __gup_longterm_locked->check_and_migrate_cma_pages() handles FOLL_LONGTERM, but in fast path, there lacks such a check, which means a possible leak of CMA page to longterm pinned. Place a check in try_grab_compound_head() in the fast path to fix the leak, and if FOLL_LONGTERM happens on CMA, it will fall back to slow path to migrate the page. Some note about the check: Huge page's subpages have the same migrate type due to either allocation from a free_list[] or alloc_contig_range() with param MIGRATE_MOVABLE. So it is enough to check on a single subpage by is_migrate_cma_page(subpage) Link: http://lkml.kernel.org/r/1584876733-17405-3-git-send-email-kernelfans@gmail.com Signed-off-by: Pingfan Liu Reviewed-by: Christoph Hellwig Reviewed-by: Jason Gunthorpe Cc: Ira Weiny Cc: Mike Rapoport Cc: Dan Williams Cc: Matthew Wilcox Cc: John Hubbard Cc: "Aneesh Kumar K.V" Cc: Christoph Hellwig Cc: Shuah Khan Cc: Jason Gunthorpe Signed-off-by: Andrew Morton --- mm/gup.c | 8 ++++++++ 1 file changed, 8 insertions(+) --- a/mm/gup.c~mm-gup-fix-omission-of-check-on-foll_longterm-in-gup-fast-path +++ a/mm/gup.c @@ -89,6 +89,14 @@ static __maybe_unused struct page *try_g int orig_refs = refs; /* + * Can't do FOLL_LONGTERM + FOLL_PIN with CMA in the gup fast + * path, so fail and let the caller fall back to the slow path. + */ + if (unlikely(flags & FOLL_LONGTERM) && + is_migrate_cma_page(page)) + return NULL; + + /* * When pinning a compound page of order > 1 (which is what * hpage_pincount_available() checks for), use an exact count to * track it, via hpage_pincount_add/_sub(). _