On Wed, 12 Jan 2022 at 16:55, James Carter <jwcart2@xxxxxxxxx> wrote:
>
> 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.
Something like
diff --git a/libsepol/src/optimize.c b/libsepol/src/optimize.c
index 8a048702..059c61f2 100644
--- a/libsepol/src/optimize.c
+++ b/libsepol/src/optimize.c
@@ -438,6 +443,15 @@ 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.
+ */
+ return FIXME;
+
type_map = build_type_map(p);
if (!type_map)
return -1;
?
Should it return 0 and silently not optimize or fail with -1?
In case of a failure should there be a message, e.g.
ERR(NULL, "Optimizing policy versions between 20 and 23 is not supported");
?
> 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
> >
