On Wed, Jan 19, 2022 at 10:43 AM Christian Göttsche
<cgzones@xxxxxxxxxxxxxx> wrote:
>
> 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;
>
Yes.
> ?
> 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");
>
> ?
>
Fail with -1 and the error message you have there.
Thanks,
Jim
> > 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
> > >
