iommufd/selftest: Fix buffer read overrrun in the dirty test

test_bit() is used to read the memory storing the bitmap, however
test_bit() always uses a unsigned long 8 byte access.

If the bitmap is not an aligned size of 64 bits this will now trigger a
KASAN warning reading past the end of the buffer.

Properly round the buffer allocation to an unsigned long size. Continue to
copy_from_user() using a byte granularity.

Fixes: 9560393b830b ("iommufd/selftest: Fix iommufd_test_dirty() to handle <u8 bitmaps")
Link: https://patch.msgid.link/r/0-v1-113e8d9e7861+5ae-iommufd_kasan_jgg@nvidia.com
Reviewed-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

diff --git a/drivers/iommu/iommufd/selftest.c b/drivers/iommu/iommufd/selftest.c
index 04293b20e20c9ee4df95b6c9605c4d04819b98df..c5c14bbf723cb97fa2933eecd591678b8b819473 100644 (file)
--- a/drivers/iommu/iommufd/selftest.c
+++ b/drivers/iommu/iommufd/selftest.c
@@ -1343,7 +1343,7 @@ static int iommufd_test_dirty(struct iommufd_ucmd *ucmd, unsigned int mockpt_id,
                              unsigned long page_size, void __user *uptr,
                              u32 flags)
 {
-       unsigned long bitmap_size, i, max;
+       unsigned long i, max;
        struct iommu_test_cmd *cmd = ucmd->cmd;
        struct iommufd_hw_pagetable *hwpt;
        struct mock_iommu_domain *mock;
@@ -1364,15 +1364,14 @@ static int iommufd_test_dirty(struct iommufd_ucmd *ucmd, unsigned int mockpt_id,
        }
 
        max = length / page_size;
-       bitmap_size = DIV_ROUND_UP(max, BITS_PER_BYTE);
-
-       tmp = kvzalloc(bitmap_size, GFP_KERNEL_ACCOUNT);
+       tmp = kvzalloc(DIV_ROUND_UP(max, BITS_PER_LONG) * sizeof(unsigned long),
+                      GFP_KERNEL_ACCOUNT);
        if (!tmp) {
                rc = -ENOMEM;
                goto out_put;
        }
 
-       if (copy_from_user(tmp, uptr, bitmap_size)) {
+       if (copy_from_user(tmp, uptr,DIV_ROUND_UP(max, BITS_PER_BYTE))) {
                rc = -EFAULT;
                goto out_free;
        }