On Mon, Dec 11, 2023 at 9:54 AM Christian Göttsche <cgzones@xxxxxxxxxxxxxx> wrote: > > Use a growing dynamically allocated buffer to format permission names of > an access vector instead of a fixed static buffer to support very long > permission names. > > This changes the behavior of the since libsepol 3.4 exported function > sepol_av_perm_to_string(): previously it returned a pointer to a static > buffer which must not be free'd by the caller, now an allocated string > which should be free'd by the caller (to avoid memory leaks). > > Reported-by: oss-fuzz (issue 64832, 64933) > Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx> I like this patch and would like to merge it, but it does change an exported function (by removing const on the return type). As far as I know, the only thing that uses the function externally is sepol_compute_av in libsepol/utils and the function has only been exported since 2022, so I doubt there would be any harm in making the change. But I am still hesitant to make the change. What is the best way to handle this? Jim > --- > The oss-fuzz issue 64832 got closed by the latest fuzzer updates (due to > unrelated changes that invalid the current reproducer), but the issue is > still valid. > > Supersedes https://patchwork.kernel.org/project/selinux/patch/20231207165319.63889-1-cgzones@xxxxxxxxxxxxxx/ > --- > checkpolicy/test/dismod.c | 11 +++-- > checkpolicy/test/dispol.c | 7 ++-- > libsepol/include/sepol/policydb/services.h | 5 +-- > libsepol/include/sepol/policydb/util.h | 2 +- > libsepol/src/assertion.c | 16 +++++-- > libsepol/src/hierarchy.c | 7 +++- > libsepol/src/kernel_to_cil.c | 7 ++++ > libsepol/src/kernel_to_conf.c | 15 +++++-- > libsepol/src/module_to_cil.c | 7 ++++ > libsepol/src/services.c | 8 ++-- > libsepol/src/util.c | 49 ++++++++++++---------- > libsepol/utils/sepol_compute_av.c | 25 ++++++++--- > 12 files changed, 106 insertions(+), 53 deletions(-) > > diff --git a/checkpolicy/test/dismod.c b/checkpolicy/test/dismod.c > index ac2d61d2..bd45c95e 100644 > --- a/checkpolicy/test/dismod.c > +++ b/checkpolicy/test/dismod.c > @@ -118,12 +118,11 @@ static __attribute__((__noreturn__)) void usage(const char *progname) > static void render_access_mask(uint32_t mask, uint32_t class, policydb_t * p, > FILE * fp) > { > - char *perm; > + char *perm = sepol_av_to_string(p, class, mask); > fprintf(fp, "{"); > - perm = sepol_av_to_string(p, class, mask); > - if (perm) > - fprintf(fp, "%s ", perm); > + fprintf(fp, "%s ", perm ?: "<format-failure>"); > fprintf(fp, "}"); > + free(perm); > } > > static void render_access_bitmap(ebitmap_t * map, uint32_t class, > @@ -135,8 +134,8 @@ static void render_access_bitmap(ebitmap_t * map, uint32_t class, > for (i = ebitmap_startbit(map); i < ebitmap_length(map); i++) { > if (ebitmap_get_bit(map, i)) { > perm = sepol_av_to_string(p, class, UINT32_C(1) << i); > - if (perm) > - fprintf(fp, "%s", perm); > + fprintf(fp, "%s", perm ?: "<format-failure>"); > + free(perm); > } > } > fprintf(fp, " }"); > diff --git a/checkpolicy/test/dispol.c b/checkpolicy/test/dispol.c > index 944ef7ec..2662048e 100644 > --- a/checkpolicy/test/dispol.c > +++ b/checkpolicy/test/dispol.c > @@ -93,12 +93,11 @@ static __attribute__((__noreturn__)) void usage(const char *progname) > static int render_access_mask(uint32_t mask, avtab_key_t * key, policydb_t * p, > FILE * fp) > { > - char *perm; > + char *perm = sepol_av_to_string(p, key->target_class, mask); > fprintf(fp, "{"); > - perm = sepol_av_to_string(p, key->target_class, mask); > - if (perm) > - fprintf(fp, "%s ", perm); > + fprintf(fp, "%s ", perm ?: "<format-failure>"); > fprintf(fp, "}"); > + free(perm); > return 0; > } > > diff --git a/libsepol/include/sepol/policydb/services.h b/libsepol/include/sepol/policydb/services.h > index f2e311aa..c5889da5 100644 > --- a/libsepol/include/sepol/policydb/services.h > +++ b/libsepol/include/sepol/policydb/services.h > @@ -106,10 +106,9 @@ extern int sepol_string_to_av_perm(sepol_security_class_t tclass, > /* > * Return a string representation of the permission av bit associated with > * tclass. > - * Returns a pointer to an internal buffer, overridden by the next call to > - * this function or sepol_av_to_string(). > + * The returned string must be free'd by the caller using free(3). > */ > - extern const char *sepol_av_perm_to_string(sepol_security_class_t tclass, > +extern char *sepol_av_perm_to_string(sepol_security_class_t tclass, > sepol_access_vector_t av); > > /* > diff --git a/libsepol/include/sepol/policydb/util.h b/libsepol/include/sepol/policydb/util.h > index db8da213..70c531d3 100644 > --- a/libsepol/include/sepol/policydb/util.h > +++ b/libsepol/include/sepol/policydb/util.h > @@ -31,7 +31,7 @@ extern "C" { > > extern int add_i_to_a(uint32_t i, uint32_t * cnt, uint32_t ** a); > > -extern char *sepol_av_to_string(policydb_t * policydbp, uint32_t tclass, > +extern char *sepol_av_to_string(const policydb_t *policydbp, sepol_security_class_t tclass, > sepol_access_vector_t av); > > char *sepol_extended_perms_to_string(avtab_extended_perms_t *xperms); > diff --git a/libsepol/src/assertion.c b/libsepol/src/assertion.c > index 6de7d031..3076babe 100644 > --- a/libsepol/src/assertion.c > +++ b/libsepol/src/assertion.c > @@ -48,26 +48,30 @@ static void report_failure(sepol_handle_t *handle, policydb_t *p, const avrule_t > unsigned int stype, unsigned int ttype, > const class_perm_node_t *curperm, uint32_t perms) > { > + char *permstr = sepol_av_to_string(p, curperm->tclass, perms); > + > if (avrule->source_filename) { > ERR(handle, "neverallow on line %lu of %s (or line %lu of %s) violated by allow %s %s:%s {%s };", > avrule->source_line, avrule->source_filename, avrule->line, policy_name(p), > p->p_type_val_to_name[stype], > p->p_type_val_to_name[ttype], > p->p_class_val_to_name[curperm->tclass - 1], > - sepol_av_to_string(p, curperm->tclass, perms)); > + permstr ?: "<format-failure>"); > } else if (avrule->line) { > ERR(handle, "neverallow on line %lu violated by allow %s %s:%s {%s };", > avrule->line, p->p_type_val_to_name[stype], > p->p_type_val_to_name[ttype], > p->p_class_val_to_name[curperm->tclass - 1], > - sepol_av_to_string(p, curperm->tclass, perms)); > + permstr ?: "<format-failure>"); > } else { > ERR(handle, "neverallow violated by allow %s %s:%s {%s };", > p->p_type_val_to_name[stype], > p->p_type_val_to_name[ttype], > p->p_class_val_to_name[curperm->tclass - 1], > - sepol_av_to_string(p, curperm->tclass, perms)); > + permstr ?: "<format-failure>"); > } > + > + free(permstr); > } > > static int match_any_class_permissions(class_perm_node_t *cp, uint32_t class, uint32_t data) > @@ -200,13 +204,17 @@ static int report_assertion_extended_permissions(sepol_handle_t *handle, > > /* failure on the regular permissions */ > if (!found_xperm) { > + char *permstr = sepol_av_to_string(p, curperm->tclass, perms); > + > ERR(handle, "neverallowxperm on line %lu of %s (or line %lu of %s) violated by\n" > "allow %s %s:%s {%s };", > avrule->source_line, avrule->source_filename, avrule->line, policy_name(p), > p->p_type_val_to_name[stype], > p->p_type_val_to_name[ttype], > p->p_class_val_to_name[curperm->tclass - 1], > - sepol_av_to_string(p, curperm->tclass, perms)); > + permstr ?: "<format-failure>"); > + > + free(permstr); > errors++; > > } > diff --git a/libsepol/src/hierarchy.c b/libsepol/src/hierarchy.c > index 350443a8..06e05310 100644 > --- a/libsepol/src/hierarchy.c > +++ b/libsepol/src/hierarchy.c > @@ -443,12 +443,15 @@ static void bounds_report(sepol_handle_t *handle, policydb_t *p, uint32_t child, > p->p_type_val_to_name[child - 1], > p->p_type_val_to_name[parent - 1]); > for (; cur; cur = cur->next) { > + char *permstr = sepol_av_to_string(p, cur->key.target_class, cur->datum.data); > + > ERR(handle, " %s %s : %s { %s }", > p->p_type_val_to_name[cur->key.source_type - 1], > p->p_type_val_to_name[cur->key.target_type - 1], > p->p_class_val_to_name[cur->key.target_class - 1], > - sepol_av_to_string(p, cur->key.target_class, > - cur->datum.data)); > + permstr ?: "<format-failure>"); > + > + free(permstr); > } > } > > diff --git a/libsepol/src/kernel_to_cil.c b/libsepol/src/kernel_to_cil.c > index bcb58eee..634826d5 100644 > --- a/libsepol/src/kernel_to_cil.c > +++ b/libsepol/src/kernel_to_cil.c > @@ -297,6 +297,11 @@ static int class_constraint_rules_to_strs(struct policydb *pdb, char *classkey, > } > > perms = sepol_av_to_string(pdb, class->s.value, curr->permissions); > + if (!perms) { > + ERR(NULL, "Failed to generate permission string"); > + rc = -1; > + goto exit; > + } > > if (is_mls) { > key_word = "mlsconstrain"; > @@ -307,6 +312,7 @@ static int class_constraint_rules_to_strs(struct policydb *pdb, char *classkey, > } > > rc = strs_create_and_add(strs, "(%s (%s (%s)) %s)", key_word, classkey, perms+1, expr); > + free(perms); > free(expr); > if (rc != 0) { > goto exit; > @@ -1772,6 +1778,7 @@ static char *avtab_node_to_str(struct policydb *pdb, avtab_key_t *key, avtab_dat > } > rule = create_str("(%s %s %s (%s (%s)))", > flavor, src, tgt, class, perms+1); > + free(perms); > } else if (key->specified & AVTAB_XPERMS) { > perms = xperms_to_str(datum->xperms); > if (perms == NULL) { > diff --git a/libsepol/src/kernel_to_conf.c b/libsepol/src/kernel_to_conf.c > index 83f46e0f..de1d9e09 100644 > --- a/libsepol/src/kernel_to_conf.c > +++ b/libsepol/src/kernel_to_conf.c > @@ -292,6 +292,11 @@ static int class_constraint_rules_to_strs(struct policydb *pdb, char *classkey, > } > > perms = sepol_av_to_string(pdb, class->s.value, curr->permissions); > + if (!perms) { > + ERR(NULL, "Failed to generate permission string"); > + rc = -1; > + goto exit; > + } > if (strchr(perms, ' ')) { > perm_prefix = "{ "; > perm_suffix = " }"; > @@ -311,6 +316,7 @@ static int class_constraint_rules_to_strs(struct policydb *pdb, char *classkey, > flavor, classkey, > perm_prefix, perms+1, perm_suffix, > expr); > + free(perms); > free(expr); > if (rc != 0) { > goto exit; > @@ -1682,7 +1688,7 @@ static char *avtab_node_to_str(struct policydb *pdb, avtab_key_t *key, avtab_dat > { > uint32_t data = datum->data; > type_datum_t *type; > - const char *flavor, *src, *tgt, *class, *perms, *new; > + const char *flavor, *src, *tgt, *class, *new; > char *rule = NULL, *permstring; > > switch (0xFFF & key->specified) { > @@ -1730,13 +1736,14 @@ static char *avtab_node_to_str(struct policydb *pdb, avtab_key_t *key, avtab_dat > class = pdb->p_class_val_to_name[key->target_class - 1]; > > if (key->specified & AVTAB_AV) { > - perms = sepol_av_to_string(pdb, key->target_class, data); > - if (perms == NULL) { > + permstring = sepol_av_to_string(pdb, key->target_class, data); > + if (permstring == NULL) { > ERR(NULL, "Failed to generate permission string"); > goto exit; > } > rule = create_str("%s %s %s:%s { %s };", > - flavor, src, tgt, class, perms+1); > + flavor, src, tgt, class, permstring+1); > + free(permstring); > } else if (key->specified & AVTAB_XPERMS) { > permstring = sepol_extended_perms_to_string(datum->xperms); > if (permstring == NULL) { > diff --git a/libsepol/src/module_to_cil.c b/libsepol/src/module_to_cil.c > index ee22dbbd..2ec66292 100644 > --- a/libsepol/src/module_to_cil.c > +++ b/libsepol/src/module_to_cil.c > @@ -597,6 +597,7 @@ static int avrule_to_cil(int indent, struct policydb *pdb, uint32_t type, const > rule, src, tgt, > pdb->p_class_val_to_name[classperm->tclass - 1], > perms + 1); > + free(perms); > } else { > cil_println(indent, "(%s %s %s %s %s)", > rule, src, tgt, > @@ -1967,7 +1968,13 @@ static int constraints_to_cil(int indent, struct policydb *pdb, char *classkey, > > if (is_constraint) { > perms = sepol_av_to_string(pdb, class->s.value, node->permissions); > + if (perms == NULL) { > + ERR(NULL, "Failed to generate permission string"); > + rc = -1; > + goto exit; > + } > cil_println(indent, "(%sconstrain (%s (%s)) %s)", mls, classkey, perms + 1, expr); > + free(perms); > } else { > cil_println(indent, "(%svalidatetrans %s %s)", mls, classkey, expr); > } > diff --git a/libsepol/src/services.c b/libsepol/src/services.c > index 0eeee7ec..e37221c8 100644 > --- a/libsepol/src/services.c > +++ b/libsepol/src/services.c > @@ -347,9 +347,11 @@ static char *get_class_info(sepol_security_class_t tclass, > p += len; > buf_used += len; > if (state_num < 2) { > + char *permstr = sepol_av_to_string(policydb, tclass, constraint->permissions); > + > len = snprintf(p, class_buf_len - buf_used, "{%s } (", > - sepol_av_to_string(policydb, tclass, > - constraint->permissions)); > + permstr ?: "<format-failure>"); > + free(permstr); > } else { > len = snprintf(p, class_buf_len - buf_used, "("); > } > @@ -1234,7 +1236,7 @@ out: > return STATUS_ERR; > } > > - const char *sepol_av_perm_to_string(sepol_security_class_t tclass, > +char *sepol_av_perm_to_string(sepol_security_class_t tclass, > sepol_access_vector_t av) > { > return sepol_av_to_string(policydb, tclass, av); > diff --git a/libsepol/src/util.c b/libsepol/src/util.c > index 2f877920..1d4f0005 100644 > --- a/libsepol/src/util.c > +++ b/libsepol/src/util.c > @@ -32,7 +32,7 @@ > > struct val_to_name { > unsigned int val; > - char *name; > + const char *name; > }; > > /* Add an unsigned integer to a dynamically reallocated array. *cnt > @@ -82,20 +82,26 @@ static int perm_name(hashtab_key_t key, hashtab_datum_t datum, void *data) > return 0; > } > > -char *sepol_av_to_string(policydb_t * policydbp, uint32_t tclass, > +char *sepol_av_to_string(const policydb_t *policydbp, sepol_security_class_t tclass, > sepol_access_vector_t av) > { > struct val_to_name v; > - static char avbuf[1024]; > - class_datum_t *cladatum; > - char *perm = NULL, *p; > - unsigned int i; > + const class_datum_t *cladatum = policydbp->class_val_to_struct[tclass - 1]; > + uint32_t i; > int rc; > - int avlen = 0, len; > + char *buffer = NULL, *p; > + int len; > + size_t remaining, size = 64; > + > +retry: > + if (__builtin_mul_overflow(size, 2, &size)) > + goto err; > + p = realloc(buffer, size); > + if (!p) > + goto err; > + buffer = p; > + remaining = size; > > - memset(avbuf, 0, sizeof avbuf); > - cladatum = policydbp->class_val_to_struct[tclass - 1]; > - p = avbuf; > for (i = 0; i < cladatum->permissions.nprim; i++) { > if (av & (UINT32_C(1) << i)) { > v.val = i + 1; > @@ -106,22 +112,23 @@ char *sepol_av_to_string(policydb_t * policydbp, uint32_t tclass, > permissions.table, perm_name, > &v); > } > - if (rc) > - perm = v.name; > - if (perm) { > - len = > - snprintf(p, sizeof(avbuf) - avlen, " %s", > - perm); > - if (len < 0 > - || (size_t) len >= (sizeof(avbuf) - avlen)) > - return NULL; > + if (rc == 1) { > + len = snprintf(p, remaining, " %s", v.name); > + if (len < 0) > + goto err; > + if ((size_t) len >= remaining) > + goto retry; > p += len; > - avlen += len; > + remaining -= len; > } > } > } > > - return avbuf; > + return buffer; > + > +err: > + free(buffer); > + return NULL; > } > > #define next_bit_in_range(i, p) (((i) + 1 < sizeof(p)*8) && xperm_test(((i) + 1), p)) > diff --git a/libsepol/utils/sepol_compute_av.c b/libsepol/utils/sepol_compute_av.c > index d64dc31d..2ffc7a53 100644 > --- a/libsepol/utils/sepol_compute_av.c > +++ b/libsepol/utils/sepol_compute_av.c > @@ -49,12 +49,27 @@ int main(int argc, char *argv[]) > > rc = sepol_compute_av(ssid, tsid, tclass, 0, &avd); > switch (rc) { > - case 0: > - printf("allowed: %s\n", sepol_av_perm_to_string(tclass, avd.allowed)); > - printf("decided: %s\n", sepol_av_perm_to_string(tclass, avd.decided)); > - printf("auditallow: %s\n", sepol_av_perm_to_string(tclass, avd.auditallow)); > - printf("auditdeny: %s\n", sepol_av_perm_to_string(tclass, avd.auditdeny)); > + case 0: { > + char *permstr; > + > + permstr = sepol_av_perm_to_string(tclass, avd.allowed); > + printf("allowed: %s\n", permstr ?: "<format-failure>"); > + free(permstr); > + > + permstr = sepol_av_perm_to_string(tclass, avd.decided); > + printf("decided: %s\n", permstr ?: "<format-failure>"); > + free(permstr); > + > + permstr = sepol_av_perm_to_string(tclass, avd.auditallow); > + printf("auditallow: %s\n", permstr ?: "<format-failure>"); > + free(permstr); > + > + permstr = sepol_av_perm_to_string(tclass, avd.auditdeny); > + printf("auditdeny: %s\n", permstr ?: "<format-failure>"); > + free(permstr); > + > break; > + } > case -EINVAL: > printf("Invalid request\n"); > break; > -- > 2.43.0 > >
