On 02/07/23 10:16, gregkh@xxxxxxxxxxxxxxxxxxx wrote: > > The patch below does not apply to the 5.4-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@xxxxxxxxxxxxxxx>. Updated patch below. Note that this depends on backport of upstream commit 3489dbb696d25602aea8c3e669a6d43b76bd5358 which is already queued up for 5.4-stable tree. >From 4e75ce608386f0a641455580b05e0a41d1dbba3b Mon Sep 17 00:00:00 2001 From: Mike Kravetz <mike.kravetz@xxxxxxxxxx> 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@xxxxxxxxxx Fixes: e2d8cf405525 ("migrate: add hugepage migration code to migrate_pages()") Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Acked-by: Peter Xu <peterx@xxxxxxxxxx> Acked-by: David Hildenbrand <david@xxxxxxxxxx> Cc: James Houghton <jthoughton@xxxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx> Cc: Naoya Horiguchi <naoya.horiguchi@xxxxxxxxx> Cc: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx> Cc: Yang Shi <shy828301@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/mempolicy.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/mempolicy.c b/mm/mempolicy.c index f7b231f67156..36c2a9619ba5 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); -- 2.39.1
