From: David Hildenbrand <david@redhat.com>
Date: Mon, 10 Feb 2025 19:37:44 +0000 (+0100)
Subject: mm/rmap: reject hugetlb folios in folio_make_device_exclusive()
X-Git-Tag: v6.6.88~200
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e09661ac0b84b81be4e326fa940d2096f8360d52;p=thirdparty%2Fkernel%2Fstable.git

mm/rmap: reject hugetlb folios in folio_make_device_exclusive()

commit bc3fe6805cf09a25a086573a17d40e525208c5d8 upstream.

Even though FOLL_SPLIT_PMD on hugetlb now always fails with -EOPNOTSUPP,
let's add a safety net in case FOLL_SPLIT_PMD usage would ever be
reworked.

In particular, before commit 9cb28da54643 ("mm/gup: handle hugetlb in the
generic follow_page_mask code"), GUP(FOLL_SPLIT_PMD) would just have
returned a page.  In particular, hugetlb folios that are not PMD-sized
would never have been prone to FOLL_SPLIT_PMD.

hugetlb folios can be anonymous, and page_make_device_exclusive_one() is
not really prepared for handling them at all.  So let's spell that out.

Link: https://lkml.kernel.org/r/20250210193801.781278-3-david@redhat.com
Fixes: b756a3b5e7ea ("mm: device exclusive memory access")
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Alistair Popple <apopple@nvidia.com>
Tested-by: Alistair Popple <apopple@nvidia.com>
Cc: Alex Shi <alexs@kernel.org>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Dave Airlie <airlied@gmail.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Karol Herbst <kherbst@redhat.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Lyude <lyude@redhat.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: SeongJae Park <sj@kernel.org>
Cc: Simona Vetter <simona.vetter@ffwll.ch>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yanteng Si <si.yanteng@linux.dev>
Cc: Barry Song <v-songbaohua@oppo.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/mm/rmap.c b/mm/rmap.c
index 9f795b93cf40f..968b85a67b1a1 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -2296,7 +2296,7 @@ static bool folio_make_device_exclusive(struct folio *folio,
 	 * Restrict to anonymous folios for now to avoid potential writeback
 	 * issues.
 	 */
-	if (!folio_test_anon(folio))
+	if (!folio_test_anon(folio) || folio_test_hugetlb(folio))
 		return false;
 
 	rmap_walk(folio, &rwc);