On Tue, Feb 22, 2022 at 12:05:34PM -0800, Reinette Chatre wrote:
> Hi Jarkko,
>
> On 2/20/2022 12:02 PM, Jarkko Sakkinen wrote:
> > 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>
> >
>
> Thank you very much for taking a look at these patches.
>
> V3[1] was submitted (8 February) and merged (11 February) onto x86/sgx
> before I received your reviewed-by tags for V1 (15 February) or
> V2 (20 February). The merged version thus does not contain your tags.
>
> Reinette
>
> [1] https://lore.kernel.org/linux-sgx/cover.1644355600.git.reinette.chatre@xxxxxxxxx/
Not a big deal, but thanks for confirming :-)
BR, Jarkko
