On Tue, Feb 01, 2022 at 02:47:03PM -0800, Reinette Chatre wrote:
> == Background ==
>
> The SGX selftests track parts of the enclave binaries in an array:
> encl->segment_tbl[]. That array is dynamically allocated early
> (but not first) in the test's lifetime. The array is referenced
> at the end of the test in encl_delete().
>
> == Problem ==
>
> encl->segment_tbl[] can be NULL if the test fails before its
> allocation. That leads to a NULL-pointer-dereference in encl_delete().
> This is triggered during early failures of the selftest like if the
> enclave binary ("test_encl.elf") is deleted.
>
> == Solution ==
>
> Ensure encl->segment_tbl[] is valid before attempting to access
> its members. The offset with which it is accessed, encl->nr_segments,
> is initialized before encl->segment_tbl[] and thus considered valid
> to use after the encl->segment_tbl[] check succeeds.
>
> Fixes: 3200505d4de6 ("selftests/sgx: Create a heap for the test enclave")
> Signed-off-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
> ---
> Changes since V1:
> - Rewrite commit message (Dave).
>
> tools/testing/selftests/sgx/load.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/tools/testing/selftests/sgx/load.c b/tools/testing/selftests/sgx/load.c
> index 9d4322c946e2..006b464c8fc9 100644
> --- a/tools/testing/selftests/sgx/load.c
> +++ b/tools/testing/selftests/sgx/load.c
> @@ -21,7 +21,7 @@
>
> void encl_delete(struct encl *encl)
> {
> - struct encl_segment *heap_seg = &encl->segment_tbl[encl->nr_segments - 1];
> + struct encl_segment *heap_seg;
>
> if (encl->encl_base)
> munmap((void *)encl->encl_base, encl->encl_size);
> @@ -32,10 +32,11 @@ void encl_delete(struct encl *encl)
> if (encl->fd)
> close(encl->fd);
>
> - munmap(heap_seg->src, heap_seg->size);
> -
> - if (encl->segment_tbl)
> + if (encl->segment_tbl) {
> + heap_seg = &encl->segment_tbl[encl->nr_segments - 1];
> + munmap(heap_seg->src, heap_seg->size);
> free(encl->segment_tbl);
> + }
>
> memset(encl, 0, sizeof(*encl));
> }
> --
> 2.25.1
>
Reviewed-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
BR, Jarkko
