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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 <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
This commit is contained in:
Elena Reshetova 2017-03-31 15:20:48 +03:00 committed by James Morris
parent 8291798dcf
commit fff292914d
6 changed files with 13 additions and 12 deletions
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5
include/linux/key.h
View File

@ -23,6 +23,7 @@
#include <linux/rwsem.h>
#include <linux/atomic.h>
#include <linux/assoc_array.h>
#include <linux/refcount.h>
#ifdef __KERNEL__
#include <linux/uidgid.h>
@ -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;
}

2
security/keys/gc.c
View File

@ -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)) {

6
security/keys/key.c
View File

@ -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()

8
security/keys/keyring.c
View File

@ -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);

2
security/keys/proc.c
View File

@ -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),

2
security/keys/request_key_auth.c
View File

@ -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: