powerpc/64s/hash: Fix 128TB-512TB virtual address boundary case allocation

When allocating VA space with a hint that crosses 128TB, the SLB
addr_limit variable is not expanded if addr is not > 128TB, but the
slice allocation looks at task_size, which is 512TB. This results in
slice_check_fit() incorrectly succeeding because the slice_count
truncates off bit 128 of the requested mask, so the comparison to the
available mask succeeds.

Fix this by using mm->context.addr_limit instead of mm->task_size for
testing allocation limits. This causes such allocations to fail.

Fixes: f4ea6dcb08ea ("powerpc/mm: Enable mappings above 128TB")
Cc: stable@vger.kernel.org # v4.12+
Reported-by: Florian Weimer <fweimer@redhat.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
index 48a5312..3889201 100644 (file)
--- a/arch/powerpc/mm/slice.c
+++ b/arch/powerpc/mm/slice.c
@@ -96,7 +96,7 @@ static int slice_area_is_free(struct mm_struct *mm, unsigned long addr,
 {
        struct vm_area_struct *vma;
 
-       if ((mm->task_size - len) < addr)
+       if ((mm->context.addr_limit - len) < addr)
                return 0;
        vma = find_vma(mm, addr);
        return (!vma || (addr + len) <= vm_start_gap(vma));
@@ -133,7 +133,7 @@ static void slice_mask_for_free(struct mm_struct *mm, struct slice_mask *ret)
                if (!slice_low_has_vma(mm, i))
                        ret->low_slices |= 1u << i;
 
-       if (mm->task_size <= SLICE_LOW_TOP)
+       if (mm->context.addr_limit <= SLICE_LOW_TOP)
                return;
 
        for (i = 0; i < GET_HIGH_SLICE_INDEX(mm->context.addr_limit); i++)
@@ -412,25 +412,31 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
        struct slice_mask compat_mask;
        int fixed = (flags & MAP_FIXED);
        int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT);
+       unsigned long page_size = 1UL << pshift;
        struct mm_struct *mm = current->mm;
        unsigned long newaddr;
        unsigned long high_limit;
 
-       /*
-        * Check if we need to expland slice area.
-        */
-       if (unlikely(addr >= mm->context.addr_limit &&
-                    mm->context.addr_limit != TASK_SIZE)) {
-               mm->context.addr_limit = TASK_SIZE;
+       high_limit = DEFAULT_MAP_WINDOW;
+       if (addr >= high_limit)
+               high_limit = TASK_SIZE;
+
+       if (len > high_limit)
+               return -ENOMEM;
+       if (len & (page_size - 1))
+               return -EINVAL;
+       if (fixed) {
+               if (addr & (page_size - 1))
+                       return -EINVAL;
+               if (addr > high_limit - len)
+                       return -ENOMEM;
+       }
+
+       if (high_limit > mm->context.addr_limit) {
+               mm->context.addr_limit = high_limit;
                on_each_cpu(slice_flush_segments, mm, 1);
        }
-       /*
-        * This mmap request can allocate upt to 512TB
-        */
-       if (addr >= DEFAULT_MAP_WINDOW)
-               high_limit = mm->context.addr_limit;
-       else
-               high_limit = DEFAULT_MAP_WINDOW;
+
        /*
         * init different masks
         */
@@ -446,27 +452,19 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
 
        /* Sanity checks */
        BUG_ON(mm->task_size == 0);
+       BUG_ON(mm->context.addr_limit == 0);
        VM_BUG_ON(radix_enabled());
 
        slice_dbg("slice_get_unmapped_area(mm=%p, psize=%d...\n", mm, psize);
        slice_dbg(" addr=%lx, len=%lx, flags=%lx, topdown=%d\n",
                  addr, len, flags, topdown);
 
-       if (len > mm->task_size)
-               return -ENOMEM;
-       if (len & ((1ul << pshift) - 1))
-               return -EINVAL;
-       if (fixed && (addr & ((1ul << pshift) - 1)))
-               return -EINVAL;
-       if (fixed && addr > (mm->task_size - len))
-               return -ENOMEM;
-
        /* If hint, make sure it matches our alignment restrictions */
        if (!fixed && addr) {
-               addr = _ALIGN_UP(addr, 1ul << pshift);
+               addr = _ALIGN_UP(addr, page_size);
                slice_dbg(" aligned addr=%lx\n", addr);
                /* Ignore hint if it's too large or overlaps a VMA */
-               if (addr > mm->task_size - len ||
+               if (addr > high_limit - len ||
                    !slice_area_is_free(mm, addr, len))
                        addr = 0;
        }