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>

1 files changed, 24 insertions, 26 deletions

diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
index 48a5312103a1..3889201b560c 100644
--- 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;
         }