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| author | Huacai Chen <chenhuacai@loongson.cn> | 2022-11-21 12:02:57 +0100 |
|---|---|---|
| committer | Huacai Chen <chenhuacai@loongson.cn> | 2022-11-21 12:02:57 +0100 |
| commit | bf2f34a506e66e2979de6b17c337c5d4b25b4d2c (patch) | |
| tree | 1f3509616a3a1af413353d0b7bf5993aef8a1eda | |
| parent | LoongArch: Clear FPU/SIMD thread info flags for kernel thread (diff) | |
| download | linux-bf2f34a506e66e2979de6b17c337c5d4b25b4d2c.tar.xz linux-bf2f34a506e66e2979de6b17c337c5d4b25b4d2c.zip | |
LoongArch: Set _PAGE_DIRTY only if _PAGE_WRITE is set in {pmd,pte}_mkdirty()
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 <peterx@redhat.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
| -rw-r--r-- | arch/loongarch/include/asm/pgtable.h | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/arch/loongarch/include/asm/pgtable.h b/arch/loongarch/include/asm/pgtable.h index 946704bee599..debbe116f105 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; } @@ -478,7 +480,9 @@ 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; } |