This is a note to let you know that I've just added the patch titled
LoongArch: Set _PAGE_DIRTY only if _PAGE_WRITE is set in {pmd,pte}_mkdirty()
to the 6.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
loongarch-set-_page_dirty-only-if-_page_write-is-set-in-pmd-pte-_mkdirty.patch
and it can be found in the queue-6.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From bf2f34a506e66e2979de6b17c337c5d4b25b4d2c Mon Sep 17 00:00:00 2001
From: Huacai Chen <chenhuacai@xxxxxxxxxxx>
Date: Mon, 21 Nov 2022 19:02:57 +0800
Subject: LoongArch: Set _PAGE_DIRTY only if _PAGE_WRITE is set in {pmd,pte}_mkdirty()
From: Huacai Chen <chenhuacai@xxxxxxxxxxx>
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@xxxxxxxxxxxxxxx
Cc: Peter Xu <peterx@xxxxxxxxxx>
Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/loongarch/include/asm/pgtable.h | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
--- 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 pt
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 pm
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;
}
Patches currently in stable-queue which might be from chenhuacai@xxxxxxxxxxx are
queue-6.0/loongarch-clear-fpu-simd-thread-info-flags-for-kernel-thread.patch
queue-6.0/loongarch-set-_page_dirty-only-if-_page_write-is-set-in-pmd-pte-_mkdirty.patch
