On 02/07/23 10:16, gregkh@linuxfoundation.org wrote:
The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
Updated patch below. Note that this depends on backport of upstream commit 3489dbb696d25602aea8c3e669a6d43b76bd5358 which is already queued up for 4.19-stable tree.
From 8f863a8bae356277b55b2ff909a52d12be5398a6 Mon Sep 17 00:00:00 2001 From: Mike Kravetz mike.kravetz@oracle.com Date: Thu, 26 Jan 2023 14:27:21 -0800 Subject: [PATCH] migrate: hugetlb: check for hugetlb shared PMD in node migration
commit 73bdf65ea74857d7fb2ec3067a3cec0e261b1462 upstream.
migrate_pages/mempolicy semantics state that CAP_SYS_NICE is required to move pages shared with another process to a different node. page_mapcount
1 is being used to determine if a hugetlb page is shared. However, a
hugetlb page will have a mapcount of 1 if mapped by multiple processes via a shared PMD. As a result, hugetlb pages shared by multiple processes and mapped with a shared PMD can be moved by a process without CAP_SYS_NICE.
To fix, check for a shared PMD if mapcount is 1. If a shared PMD is found consider the page shared.
Link: https://lkml.kernel.org/r/20230126222721.222195-3-mike.kravetz@oracle.com Fixes: e2d8cf405525 ("migrate: add hugepage migration code to migrate_pages()") Signed-off-by: Mike Kravetz mike.kravetz@oracle.com Acked-by: Peter Xu peterx@redhat.com Acked-by: David Hildenbrand david@redhat.com Cc: James Houghton jthoughton@google.com Cc: Matthew Wilcox willy@infradead.org Cc: Michal Hocko mhocko@suse.com Cc: Muchun Song songmuchun@bytedance.com Cc: Naoya Horiguchi naoya.horiguchi@linux.dev Cc: Vishal Moola (Oracle) vishal.moola@gmail.com Cc: Yang Shi shy828301@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org --- mm/mempolicy.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/mempolicy.c b/mm/mempolicy.c index e44e737e90a3..35088e830bff 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -571,7 +571,8 @@ static int queue_pages_hugetlb(pte_t *pte, unsigned long hmask, goto unlock; /* With MPOL_MF_MOVE, we migrate only unshared hugepage. */ if (flags & (MPOL_MF_MOVE_ALL) || - (flags & MPOL_MF_MOVE && page_mapcount(page) == 1)) + (flags & MPOL_MF_MOVE && page_mapcount(page) == 1 && + !hugetlb_pmd_shared(pte))) isolate_huge_page(page, qp->pagelist); unlock: spin_unlock(ptl);