| Message ID | 20240228204356.1809886-1-jwcart2@gmail.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | fe16f586d5e1 |
| Delegated to: | Petr Lautrbach |
| Headers | show |
| Series | [v3] checkpolicy, libsepol: Fix potential double free of mls_level_t | expand |
On Wed, Feb 28, 2024 at 3:43 PM James Carter <jwcart2@gmail.com> wrote: > > In checkpolicy, a sensitivity that has one or more aliases will > temporarily share the mls_level_t structure with its aliases until > a level statement is processed for the sensitivity (or one of the > aliases) and the aliases are updated to have their own mls_level_t > structure. If the policydb is destroyed while they are sharing the > mls_level_t structure, then a double free of the shared mls_level_t > will occur. This does not currently occur only because checkpolicy > does very little clean-up before exiting. > > The "defined" field of the level_datum_t is set after a level > statement is processed for a sensitivity and its aliases. This means > that we know an alias has its own mls_level_t if the "defined" field > is set. The double free can be avoided by not destroying the > mls_leve_t structure for an alias unless the "defined" field is set. > > Since the "defined" field is only set to false while the mls_level_t > structure is being shared, it would be clearer to rename the field > as "notdefined". It would only be set during the time the sensitivity > and its aliases are sharing the mls_level_t structure. Outside of > checkpolicy, the "notdefined" field will always be set to 0. > > Also, do more validation of the level_datum_t when validating the > policydb. > > Signed-off-by: James Carter <jwcart2@gmail.com> This patch has been merged. Jim > --- > v3: Add a comment about the "notdefined" field in the definition of level_datum_t. > Do more validation of the level_datum_t when validating the policydb. > v2: Change the field name from "defined" to "notdefined" and change > the logic to match. > > checkpolicy/checkpolicy.c | 7 ++--- > checkpolicy/policy_define.c | 10 ++++--- > libsepol/cil/src/cil_binary.c | 3 -- > libsepol/include/sepol/policydb/policydb.h | 2 +- > libsepol/src/policydb.c | 6 ++-- > libsepol/src/policydb_validate.c | 35 ++++++++++++++++++---- > 6 files changed, 44 insertions(+), 19 deletions(-) > > diff --git a/checkpolicy/checkpolicy.c b/checkpolicy/checkpolicy.c > index fcec6e51..d7cafaa4 100644 > --- a/checkpolicy/checkpolicy.c > +++ b/checkpolicy/checkpolicy.c > @@ -370,10 +370,9 @@ static int check_level(hashtab_key_t key, hashtab_datum_t datum, void *arg __att > { > level_datum_t *levdatum = (level_datum_t *) datum; > > - if (!levdatum->isalias && !levdatum->defined) { > - fprintf(stderr, > - "Error: sensitivity %s was not used in a level definition!\n", > - key); > + if (!levdatum->isalias && levdatum->notdefined) { > + fprintf(stderr, "Error: sensitivity %s was not used in a level definition!\n", > + key); > return -1; > } > return 0; > diff --git a/checkpolicy/policy_define.c b/checkpolicy/policy_define.c > index 260e609d..ac215086 100644 > --- a/checkpolicy/policy_define.c > +++ b/checkpolicy/policy_define.c > @@ -743,6 +743,7 @@ int define_sens(void) > level_datum_init(datum); > datum->isalias = FALSE; > datum->level = level; > + datum->notdefined = TRUE; > > ret = declare_symbol(SYM_LEVELS, id, datum, &value, &value); > switch (ret) { > @@ -780,6 +781,7 @@ int define_sens(void) > level_datum_init(aliasdatum); > aliasdatum->isalias = TRUE; > aliasdatum->level = level; > + aliasdatum->notdefined = TRUE; > > ret = declare_symbol(SYM_LEVELS, id, aliasdatum, NULL, &value); > switch (ret) { > @@ -1006,9 +1008,10 @@ static int clone_level(hashtab_key_t key __attribute__ ((unused)), hashtab_datum > mls_level_t *level = (mls_level_t *) arg, *newlevel; > > if (levdatum->level == level) { > - levdatum->defined = 1; > - if (!levdatum->isalias) > + if (!levdatum->isalias) { > + levdatum->notdefined = FALSE; > return 0; > + } > newlevel = (mls_level_t *) malloc(sizeof(mls_level_t)); > if (!newlevel) > return -1; > @@ -1017,6 +1020,7 @@ static int clone_level(hashtab_key_t key __attribute__ ((unused)), hashtab_datum > return -1; > } > levdatum->level = newlevel; > + levdatum->notdefined = FALSE; > } > return 0; > } > @@ -1057,8 +1061,6 @@ int define_level(void) > } > free(id); > > - levdatum->defined = 1; > - > while ((id = queue_remove(id_queue))) { > cat_datum_t *cdatum; > int range_start, range_end, i; > diff --git a/libsepol/cil/src/cil_binary.c b/libsepol/cil/src/cil_binary.c > index a8e3616a..95bd18ba 100644 > --- a/libsepol/cil/src/cil_binary.c > +++ b/libsepol/cil/src/cil_binary.c > @@ -907,7 +907,6 @@ static int cil_sensalias_to_policydb(policydb_t *pdb, struct cil_alias *cil_alia > goto exit; > } > sepol_alias->level = mls_level; > - sepol_alias->defined = 1; > sepol_alias->isalias = 1; > > return SEPOL_OK; > @@ -3163,8 +3162,6 @@ int cil_sepol_level_define(policydb_t *pdb, struct cil_sens *cil_sens) > } > } > > - sepol_level->defined = 1; > - > return SEPOL_OK; > > exit: > diff --git a/libsepol/include/sepol/policydb/policydb.h b/libsepol/include/sepol/policydb/policydb.h > index 6682069e..56d2cb01 100644 > --- a/libsepol/include/sepol/policydb/policydb.h > +++ b/libsepol/include/sepol/policydb/policydb.h > @@ -217,7 +217,7 @@ typedef struct user_datum { > typedef struct level_datum { > mls_level_t *level; /* sensitivity and associated categories */ > unsigned char isalias; /* is this sensitivity an alias for another? */ > - unsigned char defined; > + unsigned char notdefined; /* Only set to non-zero in checkpolicy */ > } level_datum_t; > > /* Category attributes */ > diff --git a/libsepol/src/policydb.c b/libsepol/src/policydb.c > index f10a8a95..0c23a7a2 100644 > --- a/libsepol/src/policydb.c > +++ b/libsepol/src/policydb.c > @@ -1390,8 +1390,10 @@ static int sens_destroy(hashtab_key_t key, hashtab_datum_t datum, void *p > if (key) > free(key); > levdatum = (level_datum_t *) datum; > - mls_level_destroy(levdatum->level); > - free(levdatum->level); > + if (!levdatum->isalias || !levdatum->notdefined) { > + mls_level_destroy(levdatum->level); > + free(levdatum->level); > + } > level_datum_destroy(levdatum); > free(levdatum); > return 0; > diff --git a/libsepol/src/policydb_validate.c b/libsepol/src/policydb_validate.c > index d86f885e..1d8de44e 100644 > --- a/libsepol/src/policydb_validate.c > +++ b/libsepol/src/policydb_validate.c > @@ -618,14 +618,39 @@ static int validate_mls_level(const mls_level_t *level, const validate_t *sens, > return -1; > } > > -static int validate_level_datum(__attribute__ ((unused)) hashtab_key_t k, hashtab_datum_t d, void *args) > +static int validate_level_datum(sepol_handle_t *handle, const level_datum_t *level, validate_t flavors[], const policydb_t *p) > { > - level_datum_t *level = d; > - validate_t *flavors = args; > + if (level->notdefined != 0) > + goto bad; > + > + if (validate_mls_level(level->level, &flavors[SYM_LEVELS], &flavors[SYM_CATS])) > + goto bad; > + > + if (level->isalias) { > + const mls_level_t *l1 = level->level; > + const mls_level_t *l2; > + const level_datum_t *actual = (level_datum_t *) hashtab_search(p->p_levels.table, p->p_sens_val_to_name[l1->sens - 1]); > + if (!actual) > + goto bad; > + l2 = actual->level; > + if (!ebitmap_cmp(&l1->cat, &l2->cat)) > + goto bad; > + } > > - return validate_mls_level(level->level, &flavors[SYM_LEVELS], &flavors[SYM_CATS]); > + return 0; > + > + bad: > + ERR(handle, "Invalid level datum"); > + return -1; > } > > +static int validate_level_datum_wrapper(__attribute__ ((unused)) hashtab_key_t k, hashtab_datum_t d, void *args) > +{ > + map_arg_t *margs = args; > + > + return validate_level_datum(margs->handle, d, margs->flavors, margs->policy); > +} > + > static int validate_mls_range(const mls_range_t *range, const validate_t *sens, const validate_t *cats) > { > if (validate_mls_level(&range->level[0], sens, cats)) > @@ -774,7 +799,7 @@ static int validate_datum_array_entries(sepol_handle_t *handle, const policydb_t > if (hashtab_map(p->p_users.table, validate_user_datum_wrapper, &margs)) > goto bad; > > - if (p->mls && hashtab_map(p->p_levels.table, validate_level_datum, flavors)) > + if (p->mls && hashtab_map(p->p_levels.table, validate_level_datum_wrapper, &margs)) > goto bad; > > if (hashtab_map(p->p_cats.table, validate_datum, &flavors[SYM_CATS])) > -- > 2.43.2 >
diff --git a/checkpolicy/checkpolicy.c b/checkpolicy/checkpolicy.c index fcec6e51..d7cafaa4 100644 --- a/checkpolicy/checkpolicy.c +++ b/checkpolicy/checkpolicy.c @@ -370,10 +370,9 @@ static int check_level(hashtab_key_t key, hashtab_datum_t datum, void *arg __att { level_datum_t *levdatum = (level_datum_t *) datum; - if (!levdatum->isalias && !levdatum->defined) { - fprintf(stderr, - "Error: sensitivity %s was not used in a level definition!\n", - key); + if (!levdatum->isalias && levdatum->notdefined) { + fprintf(stderr, "Error: sensitivity %s was not used in a level definition!\n", + key); return -1; } return 0; diff --git a/checkpolicy/policy_define.c b/checkpolicy/policy_define.c index 260e609d..ac215086 100644 --- a/checkpolicy/policy_define.c +++ b/checkpolicy/policy_define.c @@ -743,6 +743,7 @@ int define_sens(void) level_datum_init(datum); datum->isalias = FALSE; datum->level = level; + datum->notdefined = TRUE; ret = declare_symbol(SYM_LEVELS, id, datum, &value, &value); switch (ret) { @@ -780,6 +781,7 @@ int define_sens(void) level_datum_init(aliasdatum); aliasdatum->isalias = TRUE; aliasdatum->level = level; + aliasdatum->notdefined = TRUE; ret = declare_symbol(SYM_LEVELS, id, aliasdatum, NULL, &value); switch (ret) { @@ -1006,9 +1008,10 @@ static int clone_level(hashtab_key_t key __attribute__ ((unused)), hashtab_datum mls_level_t *level = (mls_level_t *) arg, *newlevel; if (levdatum->level == level) { - levdatum->defined = 1; - if (!levdatum->isalias) + if (!levdatum->isalias) { + levdatum->notdefined = FALSE; return 0; + } newlevel = (mls_level_t *) malloc(sizeof(mls_level_t)); if (!newlevel) return -1; @@ -1017,6 +1020,7 @@ static int clone_level(hashtab_key_t key __attribute__ ((unused)), hashtab_datum return -1; } levdatum->level = newlevel; + levdatum->notdefined = FALSE; } return 0; } @@ -1057,8 +1061,6 @@ int define_level(void) } free(id); - levdatum->defined = 1; - while ((id = queue_remove(id_queue))) { cat_datum_t *cdatum; int range_start, range_end, i; diff --git a/libsepol/cil/src/cil_binary.c b/libsepol/cil/src/cil_binary.c index a8e3616a..95bd18ba 100644 --- a/libsepol/cil/src/cil_binary.c +++ b/libsepol/cil/src/cil_binary.c @@ -907,7 +907,6 @@ static int cil_sensalias_to_policydb(policydb_t *pdb, struct cil_alias *cil_alia goto exit; } sepol_alias->level = mls_level; - sepol_alias->defined = 1; sepol_alias->isalias = 1; return SEPOL_OK; @@ -3163,8 +3162,6 @@ int cil_sepol_level_define(policydb_t *pdb, struct cil_sens *cil_sens) } } - sepol_level->defined = 1; - return SEPOL_OK; exit: diff --git a/libsepol/include/sepol/policydb/policydb.h b/libsepol/include/sepol/policydb/policydb.h index 6682069e..56d2cb01 100644 --- a/libsepol/include/sepol/policydb/policydb.h +++ b/libsepol/include/sepol/policydb/policydb.h @@ -217,7 +217,7 @@ typedef struct user_datum { typedef struct level_datum { mls_level_t *level; /* sensitivity and associated categories */ unsigned char isalias; /* is this sensitivity an alias for another? */ - unsigned char defined; + unsigned char notdefined; /* Only set to non-zero in checkpolicy */ } level_datum_t; /* Category attributes */ diff --git a/libsepol/src/policydb.c b/libsepol/src/policydb.c index f10a8a95..0c23a7a2 100644 --- a/libsepol/src/policydb.c +++ b/libsepol/src/policydb.c @@ -1390,8 +1390,10 @@ static int sens_destroy(hashtab_key_t key, hashtab_datum_t datum, void *p if (key) free(key); levdatum = (level_datum_t *) datum; - mls_level_destroy(levdatum->level); - free(levdatum->level); + if (!levdatum->isalias || !levdatum->notdefined) { + mls_level_destroy(levdatum->level); + free(levdatum->level); + } level_datum_destroy(levdatum); free(levdatum); return 0; diff --git a/libsepol/src/policydb_validate.c b/libsepol/src/policydb_validate.c index d86f885e..1d8de44e 100644 --- a/libsepol/src/policydb_validate.c +++ b/libsepol/src/policydb_validate.c @@ -618,14 +618,39 @@ static int validate_mls_level(const mls_level_t *level, const validate_t *sens, return -1; } -static int validate_level_datum(__attribute__ ((unused)) hashtab_key_t k, hashtab_datum_t d, void *args) +static int validate_level_datum(sepol_handle_t *handle, const level_datum_t *level, validate_t flavors[], const policydb_t *p) { - level_datum_t *level = d; - validate_t *flavors = args; + if (level->notdefined != 0) + goto bad; + + if (validate_mls_level(level->level, &flavors[SYM_LEVELS], &flavors[SYM_CATS])) + goto bad; + + if (level->isalias) { + const mls_level_t *l1 = level->level; + const mls_level_t *l2; + const level_datum_t *actual = (level_datum_t *) hashtab_search(p->p_levels.table, p->p_sens_val_to_name[l1->sens - 1]); + if (!actual) + goto bad; + l2 = actual->level; + if (!ebitmap_cmp(&l1->cat, &l2->cat)) + goto bad; + } - return validate_mls_level(level->level, &flavors[SYM_LEVELS], &flavors[SYM_CATS]); + return 0; + + bad: + ERR(handle, "Invalid level datum"); + return -1; } +static int validate_level_datum_wrapper(__attribute__ ((unused)) hashtab_key_t k, hashtab_datum_t d, void *args) +{ + map_arg_t *margs = args; + + return validate_level_datum(margs->handle, d, margs->flavors, margs->policy); +} + static int validate_mls_range(const mls_range_t *range, const validate_t *sens, const validate_t *cats) { if (validate_mls_level(&range->level[0], sens, cats)) @@ -774,7 +799,7 @@ static int validate_datum_array_entries(sepol_handle_t *handle, const policydb_t if (hashtab_map(p->p_users.table, validate_user_datum_wrapper, &margs)) goto bad; - if (p->mls && hashtab_map(p->p_levels.table, validate_level_datum, flavors)) + if (p->mls && hashtab_map(p->p_levels.table, validate_level_datum_wrapper, &margs)) goto bad; if (hashtab_map(p->p_cats.table, validate_datum, &flavors[SYM_CATS]))
In checkpolicy, a sensitivity that has one or more aliases will temporarily share the mls_level_t structure with its aliases until a level statement is processed for the sensitivity (or one of the aliases) and the aliases are updated to have their own mls_level_t structure. If the policydb is destroyed while they are sharing the mls_level_t structure, then a double free of the shared mls_level_t will occur. This does not currently occur only because checkpolicy does very little clean-up before exiting. The "defined" field of the level_datum_t is set after a level statement is processed for a sensitivity and its aliases. This means that we know an alias has its own mls_level_t if the "defined" field is set. The double free can be avoided by not destroying the mls_leve_t structure for an alias unless the "defined" field is set. Since the "defined" field is only set to false while the mls_level_t structure is being shared, it would be clearer to rename the field as "notdefined". It would only be set during the time the sensitivity and its aliases are sharing the mls_level_t structure. Outside of checkpolicy, the "notdefined" field will always be set to 0. Also, do more validation of the level_datum_t when validating the policydb. Signed-off-by: James Carter <jwcart2@gmail.com> --- v3: Add a comment about the "notdefined" field in the definition of level_datum_t. Do more validation of the level_datum_t when validating the policydb. v2: Change the field name from "defined" to "notdefined" and change the logic to match. checkpolicy/checkpolicy.c | 7 ++--- checkpolicy/policy_define.c | 10 ++++--- libsepol/cil/src/cil_binary.c | 3 -- libsepol/include/sepol/policydb/policydb.h | 2 +- libsepol/src/policydb.c | 6 ++-- libsepol/src/policydb_validate.c | 35 ++++++++++++++++++---- 6 files changed, 44 insertions(+), 19 deletions(-)