The page reclaim has an assumption writting to a page with clean pte should trigger a page fault, because there is a window between pte zero and tlb flush where a new write could come. If the new write doesn't trigger page fault, page reclaim will not notice it and think the page is clean and reclaim it. The MADV_FREE pages don't comply with the rule and the pte is just cleaned without writeprotect, so there will be no pagefault for new write. This will cause data corruption. Cc: Minchan Kim <minchan@xxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxxx> Cc: stable@xxxxxxxxxx Signed-off-by: Shaohua Li <shli@xxxxxx> --- mm/huge_memory.c | 1 + mm/madvise.c | 1 + 2 files changed, 2 insertions(+) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 9a6bd6c..9cc5de5 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1381,6 +1381,7 @@ bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, tlb->fullmm); orig_pmd = pmd_mkold(orig_pmd); orig_pmd = pmd_mkclean(orig_pmd); + orig_pmd = pmd_wrprotect(orig_pmd); set_pmd_at(mm, addr, pmd, orig_pmd); tlb_remove_pmd_tlb_entry(tlb, pmd, addr); diff --git a/mm/madvise.c b/mm/madvise.c index 0e3828e..bfb6800 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -373,6 +373,7 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr, ptent = pte_mkold(ptent); ptent = pte_mkclean(ptent); + ptent = pte_wrprotect(ptent); set_pte_at(mm, addr, pte, ptent); if (PageActive(page)) deactivate_page(page); -- 2.9.3 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
