On Mon, Nov 7, 2022 at 10:06 AM James Houghton jthoughton@google.com wrote:

This change is very similar to the change that was made for shmem [1], and it solves the same problem but for HugeTLBFS instead.

Currently, when poison is found in a HugeTLB page, the page is removed from the page cache. That means that attempting to map or read that hugepage in the future will result in a new hugepage being allocated instead of notifying the user that the page was poisoned. As [1] states, this is effectively memory corruption.

The fix is to leave the page in the page cache. If the user attempts to use a poisoned HugeTLB page with a syscall, the syscall will fail with EIO, the same error code that shmem uses. For attempts to map the page, the thread will get a BUS_MCEERR_AR SIGBUS.

[1]: commit a76054266661 ("mm: shmem: don't truncate page if memory failure happens")

Fixes: 78bb920344b8 ("mm: hwpoison: dissolve in-use hugepage in unrecoverable memory error") Cc: stable@vger.kernel.org Signed-off-by: James Houghton jthoughton@google.com Reviewed-by: Mike Kravetz mike.kravetz@oracle.com Reviewed-by: Naoya Horiguchi naoya.horiguchi@nec.com Tested-by: Naoya Horiguchi naoya.horiguchi@nec.com

Reviewed-by: Yang Shi shy828301@gmail.com

---

fs/hugetlbfs/inode.c | 13 ++++++------- mm/hugetlb.c | 4 ++++ mm/memory-failure.c | 5 ++++- 3 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index dd54f67e47fd..df7772335dc0 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -328,6 +328,12 @@ static ssize_t hugetlbfs_read_iter(struct kiocb *iocb, struct iov_iter *to) } else { unlock_page(page);

•                   if (PageHWPoison(page)) {
  

•                           put_page(page);
  

•                           retval = -EIO;
  

•                           break;
  

•                   }
  

•                   /*
                     * We have the page, copy it to user space buffer.
                     */
  

@@ -1111,13 +1117,6 @@ static int hugetlbfs_migrate_folio(struct address_space *mapping, static int hugetlbfs_error_remove_page(struct address_space *mapping, struct page *page) {

•   struct inode *inode = mapping->host;
  

•   pgoff_t index = page->index;
  

•   hugetlb_delete_from_page_cache(page);
  

•   if (unlikely(hugetlb_unreserve_pages(inode, index, index + 1, 1)))
  

•           hugetlb_fix_reserve_counts(inode);
  

•   return 0;
  

}

diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 546df97c31e4..e48f8ef45b17 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -6111,6 +6111,10 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,

    ptl = huge_pte_lock(h, dst_mm, dst_pte);

•   ret = -EIO;
  

•   if (PageHWPoison(page))
  

•           goto out_release_unlock;
  

•   /*
     * We allow to overwrite a pte marker: consider when both MISSING|WP
     * registered, we firstly wr-protect a none pte which has no page cache
  

diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 145bb561ddb3..bead6bccc7f2 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -1080,6 +1080,7 @@ static int me_huge_page(struct page_state *ps, struct page *p) int res; struct page *hpage = compound_head(p); struct address_space *mapping;

•   bool extra_pins = false;
  
    if (!PageHuge(hpage))
            return MF_DELAYED;
  

@@ -1087,6 +1088,8 @@ static int me_huge_page(struct page_state *ps, struct page *p) mapping = page_mapping(hpage); if (mapping) { res = truncate_error_page(hpage, page_to_pfn(p), mapping);

•           /* The page is kept in page cache. */
  

•           extra_pins = true;
            unlock_page(hpage);
    } else {
            unlock_page(hpage);
  

@@ -1104,7 +1107,7 @@ static int me_huge_page(struct page_state *ps, struct page *p) } }

•   if (has_extra_refcount(ps, p, false))
  

•   if (has_extra_refcount(ps, p, extra_pins))
            res = MF_FAILED;
  
    return res;
  

-- 2.38.1.431.g37b22c650d-goog