From e19b63d000d0760163d3f625358e56434e7ad0e0 Mon Sep 17 00:00:00 2001 From: Huacai Chen Date: Mon, 21 Nov 2022 19:02:57 +0800 Subject: [PATCH] LoongArch: Set _PAGE_DIRTY only if _PAGE_WRITE is set in {pmd,pte}_mkdirty() commit bf2f34a506e66e2979de6b17c337c5d4b25b4d2c upstream. Now {pmd,pte}_mkdirty() set _PAGE_DIRTY bit unconditionally, this causes random segmentation fault after commit 0ccf7f168e17bb7e ("mm/thp: carry over dirty bit when thp splits on pmd"). The reason is: when fork(), parent process use pmd_wrprotect() to clear huge page's _PAGE_WRITE and _PAGE_DIRTY (for COW); then pte_mkdirty() set _PAGE_DIRTY as well as _PAGE_MODIFIED while splitting dirty huge pages; once _PAGE_DIRTY is set, there will be no tlb modify exception so the COW machanism fails; and at last memory corruption occurred between parent and child processes. So, we should set _PAGE_DIRTY only when _PAGE_WRITE is set in {pmd,pte}_ mkdirty(). Cc: stable@vger.kernel.org Cc: Peter Xu Signed-off-by: Huacai Chen Signed-off-by: Greg Kroah-Hartman --- arch/loongarch/include/asm/pgtable.h | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/arch/loongarch/include/asm/pgtable.h b/arch/loongarch/include/asm/pgtable.h index 8ea57e2f0e04..cc0674d1b8f0 100644 --- a/arch/loongarch/include/asm/pgtable.h +++ b/arch/loongarch/include/asm/pgtable.h @@ -349,7 +349,9 @@ static inline pte_t pte_mkclean(pte_t pte) static inline pte_t pte_mkdirty(pte_t pte) { - pte_val(pte) |= (_PAGE_DIRTY | _PAGE_MODIFIED); + pte_val(pte) |= _PAGE_MODIFIED; + if (pte_val(pte) & _PAGE_WRITE) + pte_val(pte) |= _PAGE_DIRTY; return pte; } @@ -475,7 +477,9 @@ static inline pmd_t pmd_mkclean(pmd_t pmd) static inline pmd_t pmd_mkdirty(pmd_t pmd) { - pmd_val(pmd) |= (_PAGE_DIRTY | _PAGE_MODIFIED); + pmd_val(pmd) |= _PAGE_MODIFIED; + if (pmd_val(pmd) & _PAGE_WRITE) + pmd_val(pmd) |= _PAGE_DIRTY; return pmd; }