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Date: Tue, 21 Aug 2018 19:55:17 +0530 From: "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com> To: Christophe Leroy <christophe.leroy@....fr>, Benjamin Herrenschmidt <benh@...nel.crashing.org>, Paul Mackerras <paulus@...ba.org>, Michael Ellerman <mpe@...erman.id.au>, aneesh.kumar@...ux.vnet.ibm.com Cc: linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org, stable@...r.kernel.org Subject: Re: [PATCH] powerpc/nohash: fix pte_access_permitted() Christophe Leroy <christophe.leroy@....fr> writes: > Commit 5769beaf180a8 ("powerpc/mm: Add proper pte access check helper > for other platforms") replaced generic pte_access_permitted() by an > arch specific one. > > The generic one is defined as > (pte_present(pte) && (!(write) || pte_write(pte))) > > The arch specific one is open coded checking that _PAGE_USER and > _PAGE_WRITE (_PAGE_RW) flags are set, but lacking to check that > _PAGE_RO and _PAGE_PRIVILEGED are unset, leading to a useless test > on targets like the 8xx which defines _PAGE_RW and _PAGE_USER as 0. > > Commit 5fa5b16be5b31 ("powerpc/mm/hugetlb: Use pte_access_permitted > for hugetlb access check") replaced some tests performed with > pte helpers by a call to pte_access_permitted(), leading to the same > issue. > > This patch rewrites powerpc/nohash pte_access_permitted() > using pte helpers. > Thanks for fixing this. I should have used the helper instead of opencoding it on nohash platforms. This is another reason why I was also suggesting we should avoid consolidating pte accessors across platforms and user accessors instead of opencoding. https://lore.kernel.org/lkml/87lgcusc6z.fsf@linux.vnet.ibm.com/T/#u Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@...ux.ibm.com> > Fixes: 5769beaf180a8 ("powerpc/mm: Add proper pte access check helper for other platforms") > Fixes: 5fa5b16be5b31 ("powerpc/mm/hugetlb: Use pte_access_permitted for hugetlb access check") > Cc: stable@...r.kernel.org # v4.15+ > Signed-off-by: Christophe Leroy <christophe.leroy@....fr> > --- > arch/powerpc/include/asm/nohash/pgtable.h | 9 +++------ > 1 file changed, 3 insertions(+), 6 deletions(-) > > diff --git a/arch/powerpc/include/asm/nohash/pgtable.h b/arch/powerpc/include/asm/nohash/pgtable.h > index 2160be2e4339..b321c82b3624 100644 > --- a/arch/powerpc/include/asm/nohash/pgtable.h > +++ b/arch/powerpc/include/asm/nohash/pgtable.h > @@ -51,17 +51,14 @@ static inline int pte_present(pte_t pte) > #define pte_access_permitted pte_access_permitted > static inline bool pte_access_permitted(pte_t pte, bool write) > { > - unsigned long pteval = pte_val(pte); > /* > * A read-only access is controlled by _PAGE_USER bit. > * We have _PAGE_READ set for WRITE and EXECUTE > */ > - unsigned long need_pte_bits = _PAGE_PRESENT | _PAGE_USER; > - > - if (write) > - need_pte_bits |= _PAGE_WRITE; > + if (!pte_present(pte) || !pte_user(pte) || !pte_read(pte)) > + return false; > > - if ((pteval & need_pte_bits) != need_pte_bits) > + if (write && !pte_write(pte)) > return false; > > return true; > -- > 2.13.3
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