On Tue, Jan 25, 2022 at 2:43 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>
>
Acked-by: James Carter <jwcart2@xxxxxxxxx>
> ---
> v3:
> - drop extra error blocks in kernel_to_(cil|conf).c in favor of a
> simple non-NULL check, as writing policies between version 20 and
> 23 is not supported and previously checked
> - refuse to optimize policies between version 20 and 23 altogether
> and simplify NULL checks
>
> Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
> ---
> libsepol/src/kernel_to_cil.c | 10 +++++-----
> libsepol/src/kernel_to_conf.c | 8 ++++----
> libsepol/src/optimize.c | 21 +++++++++++++++++++--
> 3 files changed, 28 insertions(+), 11 deletions(-)
>
> diff --git a/libsepol/src/kernel_to_cil.c b/libsepol/src/kernel_to_cil.c
> index 18294a9a..693206d2 100644
> --- a/libsepol/src/kernel_to_cil.c
> +++ b/libsepol/src/kernel_to_cil.c
> @@ -1227,7 +1227,7 @@ 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];
> - if (type->flavor == TYPE_ATTRIB) {
> + if (type && type->flavor == TYPE_ATTRIB) {
> rc = strs_add(strs, pdb->p_type_val_to_name[i]);
> if (rc != 0) {
> goto exit;
> @@ -1357,7 +1357,7 @@ 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];
> - if (type->flavor == TYPE_TYPE && type->primary) {
> + if (type && type->flavor == TYPE_TYPE && type->primary) {
> rc = strs_add(strs, pdb->p_type_val_to_name[i]);
> if (rc != 0) {
> goto exit;
> @@ -1486,7 +1486,7 @@ 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];
> - if (type->flavor == TYPE_TYPE) {
> + if (type && type->flavor == TYPE_TYPE) {
> if (type->bounds > 0) {
> rc = strs_add(strs, pdb->p_type_val_to_name[i]);
> if (rc != 0) {
> @@ -1540,7 +1540,7 @@ 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];
> - if (attr->flavor != TYPE_ATTRIB) continue;
> + if (!attr || attr->flavor != TYPE_ATTRIB) continue;
> name = pdb->p_type_val_to_name[i];
> typemap = &pdb->attr_type_map[i];
> if (ebitmap_is_empty(typemap)) continue;
> @@ -2273,7 +2273,7 @@ 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];
> - if (type_datum->flavor == TYPE_TYPE && type_datum->primary) {
> + if (type_datum && type_datum->flavor == TYPE_TYPE && type_datum->primary) {
> rc = strs_add(strs, pdb->p_type_val_to_name[i]);
> if (rc != 0) {
> goto exit;
> diff --git a/libsepol/src/kernel_to_conf.c b/libsepol/src/kernel_to_conf.c
> index a92ba9fd..52b6c60f 100644
> --- a/libsepol/src/kernel_to_conf.c
> +++ b/libsepol/src/kernel_to_conf.c
> @@ -1210,7 +1210,7 @@ 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];
> - if (type->flavor == TYPE_ATTRIB) {
> + if (type && type->flavor == TYPE_ATTRIB) {
> rc = strs_add(strs, pdb->p_type_val_to_name[i]);
> if (rc != 0) {
> goto exit;
> @@ -1340,7 +1340,7 @@ 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];
> - if (type->flavor == TYPE_TYPE && type->primary) {
> + if (type && type->flavor == TYPE_TYPE && type->primary) {
> rc = strs_add(strs, pdb->p_type_val_to_name[i]);
> if (rc != 0) {
> goto exit;
> @@ -1460,7 +1460,7 @@ 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];
> - if (type->flavor == TYPE_TYPE) {
> + if (type && type->flavor == TYPE_TYPE) {
> if (type->bounds > 0) {
> rc = strs_add(strs, pdb->p_type_val_to_name[i]);
> if (rc != 0) {
> @@ -1583,7 +1583,7 @@ 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];
> - if (type->flavor != TYPE_TYPE || !type->primary) continue;
> + if (!type || type->flavor != TYPE_TYPE || !type->primary) continue;
> if (ebitmap_cardinality(&pdb->type_attr_map[i]) == 1) continue;
>
> rc = ebitmap_cpy(&attrmap, &pdb->type_attr_map[i]);
> diff --git a/libsepol/src/optimize.c b/libsepol/src/optimize.c
> index 8a048702..93ff2116 100644
> --- a/libsepol/src/optimize.c
> +++ b/libsepol/src/optimize.c
> @@ -31,6 +31,7 @@
> #include <sepol/policydb/policydb.h>
> #include <sepol/policydb/conditional.h>
>
> +#include "debug.h"
> #include "private.h"
>
> #define TYPE_VEC_INIT_SIZE 16
> @@ -104,6 +105,9 @@ static struct type_vec *build_type_map(const policydb_t *p)
> if (type_vec_init(&map[i]))
> goto err;
>
> + if (!p->type_val_to_struct[i])
> + continue;
> +
> if (p->type_val_to_struct[i]->flavor != TYPE_ATTRIB) {
> ebitmap_for_each_positive_bit(&p->type_attr_map[i],
> n, k) {
> @@ -114,11 +118,13 @@ 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];
> + const ebitmap_t *types_k;
>
> - if (p->type_val_to_struct[k]->flavor != TYPE_ATTRIB)
> + if (!p->type_val_to_struct[k] || 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;
> @@ -438,6 +444,17 @@ int policydb_optimize(policydb_t *p)
> if (p->policy_type != POLICY_KERN)
> return -1;
>
> + if (p->policyvers >= POLICYDB_VERSION_AVTAB && p->policyvers <= POLICYDB_VERSION_PERMISSIVE) {
> + /*
> + * For policy versions between 20 and 23, attributes exist in the policy,
> + * but only in the type_attr_map. This means that there are gaps in both
> + * the type_val_to_struct and p_type_val_to_name arrays and policy rules
> + * can refer to those gaps.
> + */
> + ERR(NULL, "Optimizing policy versions between 20 and 23 is not supported");
> + return -1;
> + }
> +
> type_map = build_type_map(p);
> if (!type_map)
> return -1;
> --
> 2.34.1
>
