Messages in this thread |  | | Subject | Re: [PATCH] powerpc/nohash: fix pte_access_permitted() | From | Christophe LEROY <> | Date | Tue, 21 Aug 2018 16:47:58 +0200 |
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Le 21/08/2018 à 16:25, Aneesh Kumar K.V a écrit : > Christophe Leroy <christophe.leroy@c-s.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.
I fully agree. I have opened a topic for that at https://github.com/linuxppc/linux/issues/177
Christophe
> > https://lore.kernel.org/lkml/87lgcusc6z.fsf@linux.vnet.ibm.com/T/#u > > Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.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@vger.kernel.org # v4.15+ >> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.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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