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authorMichal Suchanek <msuchanek@suse.de>2018-01-29 14:02:39 +0100
committerMichal Suchanek <msuchanek@suse.de>2018-01-29 14:02:40 +0100
commita6fb443d9821a40832c1b09e7434531f5bdd9bf4 (patch)
tree26143618985743647b8a970c9597d75ac1f75a1a
parentfca4cb81e399e5b0176e29dcd0462b1d852684fb (diff)
KEYS: Fix race between updating and finding a negative key
(CVE-2017-15951, bsc#1065615, bsc#1071927). suse-commit: d6cb5a23b2d31dccc81fac8f44f795e103ee7eef
-rw-r--r--include/linux/key.h45
-rw-r--r--net/dns_resolver/dns_key.c2
-rw-r--r--security/keys/big_key.c4
-rw-r--r--security/keys/encrypted-keys/encrypted.c2
-rw-r--r--security/keys/gc.c8
-rw-r--r--security/keys/key.c31
-rw-r--r--security/keys/keyctl.c9
-rw-r--r--security/keys/keyring.c10
-rw-r--r--security/keys/proc.c7
-rw-r--r--security/keys/process_keys.c2
-rw-r--r--security/keys/request_key.c7
-rw-r--r--security/keys/request_key_auth.c2
-rw-r--r--security/keys/trusted.c2
-rw-r--r--security/keys/user_defined.c4
14 files changed, 79 insertions, 56 deletions
diff --git a/include/linux/key.h b/include/linux/key.h
index 78e25aabedaf..7d9c3a8e0e4d 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -138,6 +138,11 @@ struct key_restriction {
struct key_type *keytype;
};
+enum key_state {
+ KEY_IS_UNINSTANTIATED,
+ KEY_IS_POSITIVE, /* Positively instantiated */
+};
+
/*****************************************************************************/
/*
* authentication token / access credential / keyring
@@ -169,6 +174,7 @@ struct key {
* - may not match RCU dereferenced payload
* - payload should contain own length
*/
+ short state; /* Key state (+) or rejection error (-) */
#ifdef KEY_DEBUGGING
unsigned magic;
@@ -176,17 +182,15 @@ struct key {
#endif
unsigned long flags; /* status flags (change with bitops) */
-#define KEY_FLAG_INSTANTIATED 0 /* set if key has been instantiated */
-#define KEY_FLAG_DEAD 1 /* set if key type has been deleted */
-#define KEY_FLAG_REVOKED 2 /* set if key had been revoked */
-#define KEY_FLAG_IN_QUOTA 3 /* set if key consumes quota */
-#define KEY_FLAG_USER_CONSTRUCT 4 /* set if key is being constructed in userspace */
-#define KEY_FLAG_NEGATIVE 5 /* set if key is negative */
-#define KEY_FLAG_ROOT_CAN_CLEAR 6 /* set if key can be cleared by root without permission */
-#define KEY_FLAG_INVALIDATED 7 /* set if key has been invalidated */
-#define KEY_FLAG_BUILTIN 8 /* set if key is built in to the kernel */
-#define KEY_FLAG_ROOT_CAN_INVAL 9 /* set if key can be invalidated by root without permission */
-#define KEY_FLAG_KEEP 10 /* set if key should not be removed */
+#define KEY_FLAG_DEAD 0 /* set if key type has been deleted */
+#define KEY_FLAG_REVOKED 1 /* set if key had been revoked */
+#define KEY_FLAG_IN_QUOTA 2 /* set if key consumes quota */
+#define KEY_FLAG_USER_CONSTRUCT 3 /* set if key is being constructed in userspace */
+#define KEY_FLAG_ROOT_CAN_CLEAR 4 /* set if key can be cleared by root without permission */
+#define KEY_FLAG_INVALIDATED 5 /* set if key has been invalidated */
+#define KEY_FLAG_BUILTIN 6 /* set if key is built in to the kernel */
+#define KEY_FLAG_ROOT_CAN_INVAL 7 /* set if key can be invalidated by root without permission */
+#define KEY_FLAG_KEEP 8 /* set if key should not be removed */
/* the key type and key description string
* - the desc is used to match a key against search criteria
@@ -212,7 +216,6 @@ struct key {
struct list_head name_link;
struct assoc_array keys;
};
- int reject_error;
};
/* This is set on a keyring to restrict the addition of a link to a key
@@ -351,17 +354,27 @@ extern void key_set_timeout(struct key *, unsigned);
#define KEY_NEED_SETATTR 0x20 /* Require permission to change attributes */
#define KEY_NEED_ALL 0x3f /* All the above permissions */
+static inline short key_read_state(const struct key *key)
+{
+ /* Barrier versus mark_key_instantiated(). */
+ return smp_load_acquire(&key->state);
+}
+
/**
- * key_is_instantiated - Determine if a key has been positively instantiated
+ * key_is_positive - Determine if a key has been positively instantiated
* @key: The key to check.
*
* Return true if the specified key has been positively instantiated, false
* otherwise.
*/
-static inline bool key_is_instantiated(const struct key *key)
+static inline bool key_is_positive(const struct key *key)
+{
+ return key_read_state(key) == KEY_IS_POSITIVE;
+}
+
+static inline bool key_is_negative(const struct key *key)
{
- return test_bit(KEY_FLAG_INSTANTIATED, &key->flags) &&
- !test_bit(KEY_FLAG_NEGATIVE, &key->flags);
+ return key_read_state(key) < 0;
}
#define dereference_key_rcu(KEY) \
diff --git a/net/dns_resolver/dns_key.c b/net/dns_resolver/dns_key.c
index 8737412c7b27..e1d4d898a007 100644
--- a/net/dns_resolver/dns_key.c
+++ b/net/dns_resolver/dns_key.c
@@ -224,7 +224,7 @@ static int dns_resolver_match_preparse(struct key_match_data *match_data)
static void dns_resolver_describe(const struct key *key, struct seq_file *m)
{
seq_puts(m, key->description);
- if (key_is_instantiated(key)) {
+ if (key_is_positive(key)) {
int err = PTR_ERR(key->payload.data[dns_key_error]);
if (err)
diff --git a/security/keys/big_key.c b/security/keys/big_key.c
index f3e71b44901c..b83703a624d8 100644
--- a/security/keys/big_key.c
+++ b/security/keys/big_key.c
@@ -240,7 +240,7 @@ void big_key_revoke(struct key *key)
/* clear the quota */
key_payload_reserve(key, 0);
- if (key_is_instantiated(key) &&
+ if (key_is_positive(key) &&
(size_t)key->payload.data[big_key_len] > BIG_KEY_FILE_THRESHOLD)
vfs_truncate(path, 0);
}
@@ -272,7 +272,7 @@ void big_key_describe(const struct key *key, struct seq_file *m)
seq_puts(m, key->description);
- if (key_is_instantiated(key))
+ if (key_is_positive(key))
seq_printf(m, ": %zu [%s]",
datalen,
datalen > BIG_KEY_FILE_THRESHOLD ? "file" : "buff");
diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c
index bd64a3991e26..fea053611618 100644
--- a/security/keys/encrypted-keys/encrypted.c
+++ b/security/keys/encrypted-keys/encrypted.c
@@ -854,7 +854,7 @@ static int encrypted_update(struct key *key, struct key_preparsed_payload *prep)
size_t datalen = prep->datalen;
int ret = 0;
- if (test_bit(KEY_FLAG_NEGATIVE, &key->flags))
+ if (key_is_negative(key))
return -ENOKEY;
if (datalen <= 0 || datalen > 32767 || !prep->data)
return -EINVAL;
diff --git a/security/keys/gc.c b/security/keys/gc.c
index 87cb260e4890..f01d48cb3de1 100644
--- a/security/keys/gc.c
+++ b/security/keys/gc.c
@@ -129,15 +129,15 @@ static noinline void key_gc_unused_keys(struct list_head *keys)
while (!list_empty(keys)) {
struct key *key =
list_entry(keys->next, struct key, graveyard_link);
+ short state = key->state;
+
list_del(&key->graveyard_link);
kdebug("- %u", key->serial);
key_check(key);
/* Throw away the key data if the key is instantiated */
- if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags) &&
- !test_bit(KEY_FLAG_NEGATIVE, &key->flags) &&
- key->type->destroy)
+ if (state == KEY_IS_POSITIVE && key->type->destroy)
key->type->destroy(key);
security_key_free(key);
@@ -151,7 +151,7 @@ static noinline void key_gc_unused_keys(struct list_head *keys)
}
atomic_dec(&key->user->nkeys);
- if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
+ if (state != KEY_IS_UNINSTANTIATED)
atomic_dec(&key->user->nikeys);
key_user_put(key->user);
diff --git a/security/keys/key.c b/security/keys/key.c
index bec11eefe04d..146584383b1d 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -400,6 +400,18 @@ int key_payload_reserve(struct key *key, size_t datalen)
EXPORT_SYMBOL(key_payload_reserve);
/*
+ * Change the key state to being instantiated.
+ */
+static void mark_key_instantiated(struct key *key, int reject_error)
+{
+ /* Commit the payload before setting the state; barrier versus
+ * key_read_state().
+ */
+ smp_store_release(&key->state,
+ (reject_error < 0) ? reject_error : KEY_IS_POSITIVE);
+}
+
+/*
* Instantiate a key and link it into the target keyring atomically. Must be
* called with the target keyring's semaphore writelocked. The target key's
* semaphore need not be locked as instantiation is serialised by
@@ -422,14 +434,14 @@ static int __key_instantiate_and_link(struct key *key,
mutex_lock(&key_construction_mutex);
/* can't instantiate twice */
- if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
+ if (key->state == KEY_IS_UNINSTANTIATED) {
/* instantiate the key */
ret = key->type->instantiate(key, prep);
if (ret == 0) {
/* mark the key as being instantiated */
atomic_inc(&key->user->nikeys);
- set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
+ mark_key_instantiated(key, 0);
if (test_and_clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags))
awaken = 1;
@@ -575,13 +587,10 @@ int key_reject_and_link(struct key *key,
mutex_lock(&key_construction_mutex);
/* can't instantiate twice */
- if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
+ if (key->state == KEY_IS_UNINSTANTIATED) {
/* mark the key as being negatively instantiated */
atomic_inc(&key->user->nikeys);
- key->reject_error = -error;
- smp_wmb();
- set_bit(KEY_FLAG_NEGATIVE, &key->flags);
- set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
+ mark_key_instantiated(key, -error);
now = current_kernel_time();
key->expiry = now.tv_sec + timeout;
key_schedule_gc(key->expiry + key_gc_delay);
@@ -750,8 +759,8 @@ static inline key_ref_t __key_update(key_ref_t key_ref,
ret = key->type->update(key, prep);
if (ret == 0)
- /* updating a negative key instantiates it */
- clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
+ /* Updating a negative key positively instantiates it */
+ mark_key_instantiated(key, 0);
up_write(&key->sem);
@@ -994,8 +1003,8 @@ int key_update(key_ref_t key_ref, const void *payload, size_t plen)
ret = key->type->update(key, &prep);
if (ret == 0)
- /* updating a negative key instantiates it */
- clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
+ /* Updating a negative key positively instantiates it */
+ mark_key_instantiated(key, 0);
up_write(&key->sem);
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 6a82090c7fc1..2eb624c0aefc 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -766,10 +766,9 @@ long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen)
key = key_ref_to_ptr(key_ref);
- if (test_bit(KEY_FLAG_NEGATIVE, &key->flags)) {
- ret = -ENOKEY;
- goto error2;
- }
+ ret = key_read_state(key);
+ if (ret < 0)
+ goto error2; /* Negatively instantiated */
/* see if we can read it directly */
ret = key_permission(key_ref, KEY_NEED_READ);
@@ -901,7 +900,7 @@ long keyctl_chown_key(key_serial_t id, uid_t user, gid_t group)
atomic_dec(&key->user->nkeys);
atomic_inc(&newowner->nkeys);
- if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
+ if (key->state != KEY_IS_UNINSTANTIATED) {
atomic_dec(&key->user->nikeys);
atomic_inc(&newowner->nikeys);
}
diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index b9893fb68e4a..78e2c7b04013 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -414,7 +414,7 @@ static void keyring_describe(const struct key *keyring, struct seq_file *m)
else
seq_puts(m, "[anon]");
- if (key_is_instantiated(keyring)) {
+ if (key_is_positive(keyring)) {
if (keyring->keys.nr_leaves_on_tree != 0)
seq_printf(m, ": %lu", keyring->keys.nr_leaves_on_tree);
else
@@ -552,7 +552,8 @@ static int keyring_search_iterator(const void *object, void *iterator_data)
{
struct keyring_search_context *ctx = iterator_data;
const struct key *key = keyring_ptr_to_key(object);
- unsigned long kflags = key->flags;
+ unsigned long kflags = READ_ONCE(key->flags);
+ short state = READ_ONCE(key->state);
kenter("{%d}", key->serial);
@@ -596,9 +597,8 @@ static int keyring_search_iterator(const void *object, void *iterator_data)
if (ctx->flags & KEYRING_SEARCH_DO_STATE_CHECK) {
/* we set a different error code if we pass a negative key */
- if (kflags & (1 << KEY_FLAG_NEGATIVE)) {
- smp_rmb();
- ctx->result = ERR_PTR(key->reject_error);
+ if (state < 0) {
+ ctx->result = ERR_PTR(state);
kleave(" = %d [neg]", ctx->skipped_ret);
goto skipped;
}
diff --git a/security/keys/proc.c b/security/keys/proc.c
index bf08d02b6646..e6aa1b257578 100644
--- a/security/keys/proc.c
+++ b/security/keys/proc.c
@@ -182,6 +182,7 @@ static int proc_keys_show(struct seq_file *m, void *v)
unsigned long timo;
key_ref_t key_ref, skey_ref;
char xbuf[16];
+ short state;
int rc;
struct keyring_search_context ctx = {
@@ -240,17 +241,19 @@ static int proc_keys_show(struct seq_file *m, void *v)
sprintf(xbuf, "%luw", timo / (60*60*24*7));
}
+ state = key_read_state(key);
+
#define showflag(KEY, LETTER, FLAG) \
(test_bit(FLAG, &(KEY)->flags) ? LETTER : '-')
seq_printf(m, "%08x %c%c%c%c%c%c%c %5d %4s %08x %5d %5d %-9.9s ",
key->serial,
- showflag(key, 'I', KEY_FLAG_INSTANTIATED),
+ state != KEY_IS_UNINSTANTIATED ? 'I' : '-',
showflag(key, 'R', KEY_FLAG_REVOKED),
showflag(key, 'D', KEY_FLAG_DEAD),
showflag(key, 'Q', KEY_FLAG_IN_QUOTA),
showflag(key, 'U', KEY_FLAG_USER_CONSTRUCT),
- showflag(key, 'N', KEY_FLAG_NEGATIVE),
+ state < 0 ? 'N' : '-',
showflag(key, 'i', KEY_FLAG_INVALIDATED),
refcount_read(&key->usage),
xbuf,
diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
index 86bced9fdbdf..241f57c59371 100644
--- a/security/keys/process_keys.c
+++ b/security/keys/process_keys.c
@@ -728,7 +728,7 @@ try_again:
ret = -EIO;
if (!(lflags & KEY_LOOKUP_PARTIAL) &&
- !test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
+ key_read_state(key) == KEY_IS_UNINSTANTIATED)
goto invalid_key;
/* check the permissions */
diff --git a/security/keys/request_key.c b/security/keys/request_key.c
index 3d2272c06cae..5054e3196073 100644
--- a/security/keys/request_key.c
+++ b/security/keys/request_key.c
@@ -623,10 +623,9 @@ int wait_for_key_construction(struct key *key, bool intr)
intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
if (ret)
return -ERESTARTSYS;
- if (test_bit(KEY_FLAG_NEGATIVE, &key->flags)) {
- smp_rmb();
- return key->reject_error;
- }
+ ret = key_read_state(key);
+ if (ret < 0)
+ return ret;
return key_validate(key);
}
EXPORT_SYMBOL(wait_for_key_construction);
diff --git a/security/keys/request_key_auth.c b/security/keys/request_key_auth.c
index 0f062156dfb2..4e48ca3690a5 100644
--- a/security/keys/request_key_auth.c
+++ b/security/keys/request_key_auth.c
@@ -73,7 +73,7 @@ static void request_key_auth_describe(const struct key *key,
seq_puts(m, "key:");
seq_puts(m, key->description);
- if (key_is_instantiated(key))
+ if (key_is_positive(key))
seq_printf(m, " pid:%d ci:%zu", rka->pid, rka->callout_len);
}
diff --git a/security/keys/trusted.c b/security/keys/trusted.c
index 5a775f2fbe15..e0fcb17068f5 100644
--- a/security/keys/trusted.c
+++ b/security/keys/trusted.c
@@ -1066,7 +1066,7 @@ static int trusted_update(struct key *key, struct key_preparsed_payload *prep)
char *datablob;
int ret = 0;
- if (test_bit(KEY_FLAG_NEGATIVE, &key->flags))
+ if (key_is_negative(key))
return -ENOKEY;
p = key->payload.data[0];
if (!p->migratable)
diff --git a/security/keys/user_defined.c b/security/keys/user_defined.c
index 3d8c68eba516..9f558bedba23 100644
--- a/security/keys/user_defined.c
+++ b/security/keys/user_defined.c
@@ -114,7 +114,7 @@ int user_update(struct key *key, struct key_preparsed_payload *prep)
/* attach the new data, displacing the old */
key->expiry = prep->expiry;
- if (!test_bit(KEY_FLAG_NEGATIVE, &key->flags))
+ if (key_is_positive(key))
zap = dereference_key_locked(key);
rcu_assign_keypointer(key, prep->payload.data[0]);
prep->payload.data[0] = NULL;
@@ -162,7 +162,7 @@ EXPORT_SYMBOL_GPL(user_destroy);
void user_describe(const struct key *key, struct seq_file *m)
{
seq_puts(m, key->description);
- if (key_is_instantiated(key))
+ if (key_is_positive(key))
seq_printf(m, ": %u", key->datalen);
}