powerpc/mm: Recompute hash value after a failed update

commit 36b35d5d807b7e57aff7d08e63de8b17731ee211 upstream.

If we had secondary hash flag set, we ended up modifying hash value in
the updatepp code path. Hence with a failed updatepp we will be using
a wrong hash value for the following hash insert. Fix this by
recomputing hash before insert.

Without this patch we can end up with using wrong slot number in linux
pte. That can result in us missing an hash pte update or invalidate
which can cause memory corruption or even machine check.

Fixes: 6d492ecc6489 ("powerpc/THP: Add code to handle HPTE faults for hugepages")
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Reviewed-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

diff --git a/arch/powerpc/mm/hugepage-hash64.c b/arch/powerpc/mm/hugepage-hash64.c
index 5f5e6328c21c10f5a158d84f737ace3250602d61..5061c6f676dadc9b7dd39d8ad93a7383d9fb20e3 100644 (file)
--- a/arch/powerpc/mm/hugepage-hash64.c
+++ b/arch/powerpc/mm/hugepage-hash64.c
@@ -136,7 +136,6 @@ int __hash_page_thp(unsigned long ea, unsigned long access, unsigned long vsid,
        BUG_ON(index >= 4096);
 
        vpn = hpt_vpn(ea, vsid, ssize);
-       hash = hpt_hash(vpn, shift, ssize);
        hpte_slot_array = get_hpte_slot_array(pmdp);
        if (psize == MMU_PAGE_4K) {
                /*
@@ -151,6 +150,7 @@ int __hash_page_thp(unsigned long ea, unsigned long access, unsigned long vsid,
        valid = hpte_valid(hpte_slot_array, index);
        if (valid) {
                /* update the hpte bits */
+               hash = hpt_hash(vpn, shift, ssize);
                hidx =  hpte_hash_index(hpte_slot_array, index);
                if (hidx & _PTEIDX_SECONDARY)
                        hash = ~hash;
@@ -176,6 +176,7 @@ int __hash_page_thp(unsigned long ea, unsigned long access, unsigned long vsid,
        if (!valid) {
                unsigned long hpte_group;
 
+               hash = hpt_hash(vpn, shift, ssize);
                /* insert new entry */
                pa = pmd_pfn(__pmd(old_pmd)) << PAGE_SHIFT;
                new_pmd |= _PAGE_HASHPTE;