From fff292914d3a2f1efd05ca71c2ba72a3c663201e Mon Sep 17 00:00:00 2001 From: Elena Reshetova Date: Fri, 31 Mar 2017 15:20:48 +0300 Subject: [PATCH] security, keys: convert key.usage from atomic_t to refcount_t refcount_t type and corresponding API should be used instead of atomic_t when the variable is used as a reference counter. This allows to avoid accidental refcounter overflows that might lead to use-after-free situations. Signed-off-by: Elena Reshetova Signed-off-by: Hans Liljestrand Signed-off-by: Kees Cook Signed-off-by: David Windsor Acked-by: David Howells Signed-off-by: James Morris --- include/linux/key.h | 5 +++-- security/keys/gc.c | 2 +- security/keys/key.c | 6 +++--- security/keys/keyring.c | 8 ++++---- security/keys/proc.c | 2 +- security/keys/request_key_auth.c | 2 +- 6 files changed, 13 insertions(+), 12 deletions(-) diff --git a/include/linux/key.h b/include/linux/key.h index e45212f2777e..9d9fac583dd3 100644 --- a/include/linux/key.h +++ b/include/linux/key.h @@ -23,6 +23,7 @@ #include #include #include +#include #ifdef __KERNEL__ #include @@ -135,7 +136,7 @@ static inline bool is_key_possessed(const key_ref_t key_ref) * - Kerberos TGTs and tickets */ struct key { - atomic_t usage; /* number of references */ + refcount_t usage; /* number of references */ key_serial_t serial; /* key serial number */ union { struct list_head graveyard_link; @@ -242,7 +243,7 @@ extern void key_put(struct key *key); static inline struct key *__key_get(struct key *key) { - atomic_inc(&key->usage); + refcount_inc(&key->usage); return key; } diff --git a/security/keys/gc.c b/security/keys/gc.c index addf060399e0..44789256c88c 100644 --- a/security/keys/gc.c +++ b/security/keys/gc.c @@ -220,7 +220,7 @@ continue_scanning: key = rb_entry(cursor, struct key, serial_node); cursor = rb_next(cursor); - if (atomic_read(&key->usage) == 0) + if (refcount_read(&key->usage) == 0) goto found_unreferenced_key; if (unlikely(gc_state & KEY_GC_REAPING_DEAD_1)) { diff --git a/security/keys/key.c b/security/keys/key.c index 346fbf201c22..ff9244392d35 100644 --- a/security/keys/key.c +++ b/security/keys/key.c @@ -285,7 +285,7 @@ struct key *key_alloc(struct key_type *type, const char *desc, if (!key->index_key.description) goto no_memory_3; - atomic_set(&key->usage, 1); + refcount_set(&key->usage, 1); init_rwsem(&key->sem); lockdep_set_class(&key->sem, &type->lock_class); key->index_key.type = type; @@ -621,7 +621,7 @@ void key_put(struct key *key) if (key) { key_check(key); - if (atomic_dec_and_test(&key->usage)) + if (refcount_dec_and_test(&key->usage)) schedule_work(&key_gc_work); } } @@ -656,7 +656,7 @@ not_found: found: /* pretend it doesn't exist if it is awaiting deletion */ - if (atomic_read(&key->usage) == 0) + if (refcount_read(&key->usage) == 0) goto not_found; /* this races with key_put(), but that doesn't matter since key_put() diff --git a/security/keys/keyring.c b/security/keys/keyring.c index c91e4e0cea08..3d95f7d02ba1 100644 --- a/security/keys/keyring.c +++ b/security/keys/keyring.c @@ -1033,7 +1033,7 @@ struct key *find_keyring_by_name(const char *name, bool skip_perm_check) /* we've got a match but we might end up racing with * key_cleanup() if the keyring is currently 'dead' * (ie. it has a zero usage count) */ - if (!atomic_inc_not_zero(&keyring->usage)) + if (!refcount_inc_not_zero(&keyring->usage)) continue; keyring->last_used_at = current_kernel_time().tv_sec; goto out; @@ -1250,14 +1250,14 @@ int key_link(struct key *keyring, struct key *key) struct assoc_array_edit *edit; int ret; - kenter("{%d,%d}", keyring->serial, atomic_read(&keyring->usage)); + kenter("{%d,%d}", keyring->serial, refcount_read(&keyring->usage)); key_check(keyring); key_check(key); ret = __key_link_begin(keyring, &key->index_key, &edit); if (ret == 0) { - kdebug("begun {%d,%d}", keyring->serial, atomic_read(&keyring->usage)); + kdebug("begun {%d,%d}", keyring->serial, refcount_read(&keyring->usage)); ret = __key_link_check_restriction(keyring, key); if (ret == 0) ret = __key_link_check_live_key(keyring, key); @@ -1266,7 +1266,7 @@ int key_link(struct key *keyring, struct key *key) __key_link_end(keyring, &key->index_key, edit); } - kleave(" = %d {%d,%d}", ret, keyring->serial, atomic_read(&keyring->usage)); + kleave(" = %d {%d,%d}", ret, keyring->serial, refcount_read(&keyring->usage)); return ret; } EXPORT_SYMBOL(key_link); diff --git a/security/keys/proc.c b/security/keys/proc.c index b9f531c9e4fa..69199f18bfb3 100644 --- a/security/keys/proc.c +++ b/security/keys/proc.c @@ -252,7 +252,7 @@ static int proc_keys_show(struct seq_file *m, void *v) showflag(key, 'U', KEY_FLAG_USER_CONSTRUCT), showflag(key, 'N', KEY_FLAG_NEGATIVE), showflag(key, 'i', KEY_FLAG_INVALIDATED), - atomic_read(&key->usage), + refcount_read(&key->usage), xbuf, key->perm, from_kuid_munged(seq_user_ns(m), key->uid), diff --git a/security/keys/request_key_auth.c b/security/keys/request_key_auth.c index 6bbe2f535f08..0f062156dfb2 100644 --- a/security/keys/request_key_auth.c +++ b/security/keys/request_key_auth.c @@ -213,7 +213,7 @@ struct key *request_key_auth_new(struct key *target, const void *callout_info, if (ret < 0) goto error_inst; - kleave(" = {%d,%d}", authkey->serial, atomic_read(&authkey->usage)); + kleave(" = {%d,%d}", authkey->serial, refcount_read(&authkey->usage)); return authkey; auth_key_revoked: -- 2.20.1