| Message ID | 1435752511-7079-1-git-send-email-christoffer.dall@linaro.org |
|---|---|
| State | Accepted |
| Commit | fd28f5d439fca77348c129d5b73043a56f8a0296 |
| Headers | show |
On 1 July 2015 at 13:08, Christoffer Dall <christoffer.dall@linaro.org> wrote: > The current pmd_huge() and pud_huge() functions simply check if the table > bit is not set and reports the entries as huge in that case. This is > counter-intuitive as a clear pmd/pud cannot also be a huge pmd/pud, and > it is inconsistent with at least arm and x86. > > To prevent others from making the same mistake as me in looking at code > that calls these functions and to fix an issue with KVM on arm64 that > causes memory corruption due to incorrect page reference counting > resulting from this mistake, let's change the behavior. > > Cc: stable@vger.kernel.org Thanks Christoffer. It may be worth adding: Fixes: 084bd29810a5 ("ARM64: mm: HugeTLB support.") And, please feel free to add: Reviewed-by: Steve Capper <steve.capper@linaro.org> > Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org> > --- > arch/arm64/mm/hugetlbpage.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c > index 2de9d2e..0eeb4f09 100644 > --- a/arch/arm64/mm/hugetlbpage.c > +++ b/arch/arm64/mm/hugetlbpage.c > @@ -40,13 +40,13 @@ int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep) > > int pmd_huge(pmd_t pmd) > { > - return !(pmd_val(pmd) & PMD_TABLE_BIT); > + return pmd_val(pmd) && !(pmd_val(pmd) & PMD_TABLE_BIT); > } > > int pud_huge(pud_t pud) > { > #ifndef __PAGETABLE_PMD_FOLDED > - return !(pud_val(pud) & PUD_TABLE_BIT); > + return pud_val(pud) && !(pud_val(pud) & PUD_TABLE_BIT); > #else > return 0; > #endif > -- > 2.1.2.330.g565301e.dirty > -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, Jul 01, 2015 at 01:24:34PM +0100, Steve Capper wrote: > On 1 July 2015 at 13:08, Christoffer Dall <christoffer.dall@linaro.org> wrote: > > The current pmd_huge() and pud_huge() functions simply check if the table > > bit is not set and reports the entries as huge in that case. This is > > counter-intuitive as a clear pmd/pud cannot also be a huge pmd/pud, and > > it is inconsistent with at least arm and x86. > > > > To prevent others from making the same mistake as me in looking at code > > that calls these functions and to fix an issue with KVM on arm64 that > > causes memory corruption due to incorrect page reference counting > > resulting from this mistake, let's change the behavior. > > > > Cc: stable@vger.kernel.org > > Thanks Christoffer. > > It may be worth adding: > > Fixes: 084bd29810a5 ("ARM64: mm: HugeTLB support.") > > And, please feel free to add: > > Reviewed-by: Steve Capper <steve.capper@linaro.org> > Thanks! -Christoffer -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c index 2de9d2e..0eeb4f09 100644 --- a/arch/arm64/mm/hugetlbpage.c +++ b/arch/arm64/mm/hugetlbpage.c @@ -40,13 +40,13 @@ int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep) int pmd_huge(pmd_t pmd) { - return !(pmd_val(pmd) & PMD_TABLE_BIT); + return pmd_val(pmd) && !(pmd_val(pmd) & PMD_TABLE_BIT); } int pud_huge(pud_t pud) { #ifndef __PAGETABLE_PMD_FOLDED - return !(pud_val(pud) & PUD_TABLE_BIT); + return pud_val(pud) && !(pud_val(pud) & PUD_TABLE_BIT); #else return 0; #endif
The current pmd_huge() and pud_huge() functions simply check if the table bit is not set and reports the entries as huge in that case. This is counter-intuitive as a clear pmd/pud cannot also be a huge pmd/pud, and it is inconsistent with at least arm and x86. To prevent others from making the same mistake as me in looking at code that calls these functions and to fix an issue with KVM on arm64 that causes memory corruption due to incorrect page reference counting resulting from this mistake, let's change the behavior. Cc: stable@vger.kernel.org Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org> --- arch/arm64/mm/hugetlbpage.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)