4.18-stable review patch. If anyone has any objections, please let me know.
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From: Christophe Leroy christophe.leroy@c-s.fr
commit 810e9f86f36f59f1d6f6710220c49afe0c705f38 upstream.
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.
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 Reviewed-by: Aneesh Kumar K.V aneesh.kumar@linux.ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/powerpc/include/asm/nohash/pgtable.h | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-)
--- 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;