On Fri, Jan 7, 2022 at 1:57 PM Christian Göttsche
<cgzones@xxxxxxxxxxxxxx> wrote:
>
> For policy versions between 20 and 23 the type_val_to_struct array might
> contain gaps. Skip those gaps to avoid NULL pointer dereferences:
>
> ==1250==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000008 (pc 0x00000058560b bp 0x7ffdca60c110 sp 0x7ffdca60bfc0 T0)
> ==1250==The signal is caused by a READ memory access.
> ==1250==Hint: address points to the zero page.
> #0 0x58560b in build_type_map selinux/libsepol/src/optimize.c:107:33
> #1 0x58560b in policydb_optimize selinux/libsepol/src/optimize.c:441:13
> #2 0x55e63e in LLVMFuzzerTestOneInput selinux/libsepol/fuzz/binpolicy-fuzzer.c:42:10
> #3 0x455283 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) cxa_noexception.cpp:0
> #4 0x440ec2 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerDriver.cpp:324:6
> #5 0x44671c in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) cxa_noexception.cpp:0
> #6 0x46f522 in main /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerMain.cpp:20:10
> #7 0x7f9c160d00b2 in __libc_start_main /build/glibc-eX1tMB/glibc-2.31/csu/libc-start.c:308:16
> #8 0x41f67d in _start
>
> Found by oss-fuzz (#42697)
>
> Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
> ---
> @Jim:
> I hope I have interpreted and implemented your feedback correctly, but I
> am not sure I have seen through the whole gaps logic yet.
> ---
> libsepol/src/kernel_to_cil.c | 40 +++++++++++++++++++++++++++++++++++
> libsepol/src/kernel_to_conf.c | 32 ++++++++++++++++++++++++++++
> libsepol/src/optimize.c | 18 +++++++++++++++-
> 3 files changed, 89 insertions(+), 1 deletion(-)
>
> diff --git a/libsepol/src/kernel_to_cil.c b/libsepol/src/kernel_to_cil.c
> index 18294a9a..1353e77f 100644
> --- a/libsepol/src/kernel_to_cil.c
> +++ b/libsepol/src/kernel_to_cil.c
> @@ -1227,6 +1227,14 @@ static int write_type_attributes_to_cil(FILE *out, struct policydb *pdb)
>
> for (i=0; i < pdb->p_types.nprim; i++) {
> type = pdb->type_val_to_struct[i];
> + /* Gap in types for policy versions between 20 and 23 */
> + if (!type) {
> + if (pdb->policyvers <= POLICYDB_VERSION_PERMISSIVE) {
> + rc = -1;
> + goto exit;
> + }
> + continue;
> + }
There is already a check in sepol_kernel_policydb_to_cil() and an
error is returned if the policy version is between 20 and 23.
While no policy that is written by libsepol will have gaps in this
array, the validate_policydb() only checks that gaps are not referred
to by any rules, so there does need to be a check for a NULL here.
I would make the line below to be "if (type && type->flavor ..."
> if (type->flavor == TYPE_ATTRIB) {
> rc = strs_add(strs, pdb->p_type_val_to_name[i]);
> if (rc != 0) {
> @@ -1357,6 +1365,14 @@ static int write_type_decl_rules_to_cil(FILE *out, struct policydb *pdb)
>
> for (i=0; i < pdb->p_types.nprim; i++) {
> type = pdb->type_val_to_struct[i];
> + /* Gap in types for policy versions between 20 and 23 */
> + if (!type) {
> + if (pdb->policyvers <= POLICYDB_VERSION_PERMISSIVE) {
> + rc = -1;
> + goto exit;
> + }
> + continue;
> + }
Same here.
> if (type->flavor == TYPE_TYPE && type->primary) {
> rc = strs_add(strs, pdb->p_type_val_to_name[i]);
> if (rc != 0) {
> @@ -1486,6 +1502,14 @@ static int write_type_bounds_rules_to_cil(FILE *out, struct policydb *pdb)
>
> for (i=0; i < pdb->p_types.nprim; i++) {
> type = pdb->type_val_to_struct[i];
> + /* Gap in types for policy versions between 20 and 23 */
> + if (!type) {
> + if (pdb->policyvers <= POLICYDB_VERSION_PERMISSIVE) {
> + rc = -1;
> + goto exit;
> + }
> + continue;
> + }
And here.
> if (type->flavor == TYPE_TYPE) {
> if (type->bounds > 0) {
> rc = strs_add(strs, pdb->p_type_val_to_name[i]);
> @@ -1540,6 +1564,14 @@ static int write_type_attribute_sets_to_cil(FILE *out, struct policydb *pdb)
>
> for (i=0; i < pdb->p_types.nprim; i++) {
> attr = pdb->type_val_to_struct[i];
> + /* Gap in types for policy versions between 20 and 23 */
> + if (!attr) {
> + if (pdb->policyvers <= POLICYDB_VERSION_PERMISSIVE) {
> + rc = -1;
> + goto exit;
> + }
> + continue;
> + }
And here.
> if (attr->flavor != TYPE_ATTRIB) continue;
> name = pdb->p_type_val_to_name[i];
> typemap = &pdb->attr_type_map[i];
> @@ -2273,6 +2305,14 @@ static int write_role_decl_rules_to_cil(FILE *out, struct policydb *pdb)
>
> for (i=0; i < pdb->p_types.nprim; i++) {
> type_datum = pdb->type_val_to_struct[i];
> + /* Gap in types for policy versions between 20 and 23 */
> + if (!type_datum) {
> + if (pdb->policyvers <= POLICYDB_VERSION_PERMISSIVE) {
> + rc = -1;
> + goto exit;
> + }
> + continue;
> + }
And here.
> if (type_datum->flavor == TYPE_TYPE && type_datum->primary) {
> rc = strs_add(strs, pdb->p_type_val_to_name[i]);
> if (rc != 0) {
> diff --git a/libsepol/src/kernel_to_conf.c b/libsepol/src/kernel_to_conf.c
> index a92ba9fd..235b4556 100644
> --- a/libsepol/src/kernel_to_conf.c
> +++ b/libsepol/src/kernel_to_conf.c
> @@ -1210,6 +1210,14 @@ static int write_type_attributes_to_conf(FILE *out, struct policydb *pdb)
>
> for (i=0; i < pdb->p_types.nprim; i++) {
> type = pdb->type_val_to_struct[i];
> + /* Gap in types for policy versions between 20 and 23 */
> + if (!type) {
> + if (pdb->policyvers <= POLICYDB_VERSION_PERMISSIVE) {
> + rc = -1;
> + goto exit;
> + }
> + continue;
> + }
Same thing here. sepol_kernel_policydb_to_conf() already does a check
and returns an error if the policy version is between 20 and 23. All
the same comments above apply here.
> if (type->flavor == TYPE_ATTRIB) {
> rc = strs_add(strs, pdb->p_type_val_to_name[i]);
> if (rc != 0) {
> @@ -1340,6 +1348,14 @@ static int write_type_decl_rules_to_conf(FILE *out, struct policydb *pdb)
>
> for (i=0; i < pdb->p_types.nprim; i++) {
> type = pdb->type_val_to_struct[i];
> + /* Gap in types for policy versions between 20 and 23 */
> + if (!type) {
> + if (pdb->policyvers <= POLICYDB_VERSION_PERMISSIVE) {
> + rc = -1;
> + goto exit;
> + }
> + continue;
> + }
> if (type->flavor == TYPE_TYPE && type->primary) {
> rc = strs_add(strs, pdb->p_type_val_to_name[i]);
> if (rc != 0) {
> @@ -1460,6 +1476,14 @@ static int write_type_bounds_rules_to_conf(FILE *out, struct policydb *pdb)
>
> for (i=0; i < pdb->p_types.nprim; i++) {
> type = pdb->type_val_to_struct[i];
> + /* Gap in types for policy versions between 20 and 23 */
> + if (!type) {
> + if (pdb->policyvers <= POLICYDB_VERSION_PERMISSIVE) {
> + rc = -1;
> + goto exit;
> + }
> + continue;
> + }
> if (type->flavor == TYPE_TYPE) {
> if (type->bounds > 0) {
> rc = strs_add(strs, pdb->p_type_val_to_name[i]);
> @@ -1583,6 +1607,14 @@ static int write_type_attribute_sets_to_conf(FILE *out, struct policydb *pdb)
>
> for (i=0; i < pdb->p_types.nprim; i++) {
> type = pdb->type_val_to_struct[i];
> + /* Gap in types for policy versions between 20 and 23 */
> + if (!type) {
> + if (pdb->policyvers <= POLICYDB_VERSION_PERMISSIVE) {
> + rc = -1;
> + goto exit;
> + }
> + continue;
> + }
> if (type->flavor != TYPE_TYPE || !type->primary) continue;
> if (ebitmap_cardinality(&pdb->type_attr_map[i]) == 1) continue;
>
> diff --git a/libsepol/src/optimize.c b/libsepol/src/optimize.c
> index 8a048702..f8c28313 100644
> --- a/libsepol/src/optimize.c
> +++ b/libsepol/src/optimize.c
> @@ -104,6 +104,13 @@ static struct type_vec *build_type_map(const policydb_t *p)
> if (type_vec_init(&map[i]))
> goto err;
>
> + /* Gap in types for policy versions between 20 and 23 */
> + if (!p->type_val_to_struct[i]) {
> + if (p->policyvers <= POLICYDB_VERSION_PERMISSIVE)
> + goto err;
> + continue;
> + }
> +
I want the same sort of check for the policy version done in
policydb_optimize(), not throughout the code.
Can still check for NULL.
> if (p->type_val_to_struct[i]->flavor != TYPE_ATTRIB) {
> ebitmap_for_each_positive_bit(&p->type_attr_map[i],
> n, k) {
> @@ -114,11 +121,20 @@ static struct type_vec *build_type_map(const policydb_t *p)
> ebitmap_t *types_i = &p->attr_type_map[i];
>
> for (k = 0; k < p->p_types.nprim; k++) {
> - ebitmap_t *types_k = &p->attr_type_map[k];
> + ebitmap_t *types_k;
> +
> + /* Gap in types for policy versions between 20 and 23 */
> + if (!p->type_val_to_struct[k]) {
> + if (p->policyvers <= POLICYDB_VERSION_PERMISSIVE)
> + goto err;
> + continue;
> + }
Same here.
Thanks,
Jim
>
> if (p->type_val_to_struct[k]->flavor != TYPE_ATTRIB)
> continue;
>
> + types_k = &p->attr_type_map[k];
> +
> if (ebitmap_contains(types_k, types_i)) {
> if (type_vec_append(&map[i], k))
> goto err;
> --
> 2.34.1
>
