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-rw-r--r--Documentation/networking/dns_resolver.txt4
-rw-r--r--Documentation/security/keys.txt4
-rw-r--r--fs/cifs/cifsacl.c1
-rw-r--r--fs/nfs/idmap.c1
-rw-r--r--include/linux/key.h1
-rw-r--r--net/dns_resolver/dns_key.c1
-rw-r--r--security/keys/keyctl.c15
7 files changed, 26 insertions, 1 deletions
diff --git a/Documentation/networking/dns_resolver.txt b/Documentation/networking/dns_resolver.txt
index 7f531ad8328..d86adcdae42 100644
--- a/Documentation/networking/dns_resolver.txt
+++ b/Documentation/networking/dns_resolver.txt
@@ -102,6 +102,10 @@ implemented in the module can be called after doing:
If _expiry is non-NULL, the expiry time (TTL) of the result will be
returned also.
+The kernel maintains an internal keyring in which it caches looked up keys.
+This can be cleared by any process that has the CAP_SYS_ADMIN capability by
+the use of KEYCTL_KEYRING_CLEAR on the keyring ID.
+
===============================
READING DNS KEYS FROM USERSPACE
diff --git a/Documentation/security/keys.txt b/Documentation/security/keys.txt
index 4d75931d2d7..713ec232c56 100644
--- a/Documentation/security/keys.txt
+++ b/Documentation/security/keys.txt
@@ -554,6 +554,10 @@ The keyctl syscall functions are:
process must have write permission on the keyring, and it must be a
keyring (or else error ENOTDIR will result).
+ This function can also be used to clear special kernel keyrings if they
+ are appropriately marked if the user has CAP_SYS_ADMIN capability. The
+ DNS resolver cache keyring is an example of this.
+
(*) Link a key into a keyring:
diff --git a/fs/cifs/cifsacl.c b/fs/cifs/cifsacl.c
index 72ddf23ef6f..854749d21bb 100644
--- a/fs/cifs/cifsacl.c
+++ b/fs/cifs/cifsacl.c
@@ -556,6 +556,7 @@ init_cifs_idmap(void)
/* instruct request_key() to use this special keyring as a cache for
* the results it looks up */
+ set_bit(KEY_FLAG_ROOT_CAN_CLEAR, &keyring->flags);
cred->thread_keyring = keyring;
cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
root_cred = cred;
diff --git a/fs/nfs/idmap.c b/fs/nfs/idmap.c
index 2c05f1991e1..a1bbf7780df 100644
--- a/fs/nfs/idmap.c
+++ b/fs/nfs/idmap.c
@@ -198,6 +198,7 @@ int nfs_idmap_init(void)
if (ret < 0)
goto failed_put_key;
+ set_bit(KEY_FLAG_ROOT_CAN_CLEAR, &keyring->flags);
cred->thread_keyring = keyring;
cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
id_resolver_cache = cred;
diff --git a/include/linux/key.h b/include/linux/key.h
index 183a6af7715..3ac412855d8 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -155,6 +155,7 @@ struct key {
#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 */
/* the description string
* - this is used to match a key against search criteria
diff --git a/net/dns_resolver/dns_key.c b/net/dns_resolver/dns_key.c
index fa000d26dc6..c73bba326d7 100644
--- a/net/dns_resolver/dns_key.c
+++ b/net/dns_resolver/dns_key.c
@@ -281,6 +281,7 @@ static int __init init_dns_resolver(void)
/* instruct request_key() to use this special keyring as a cache for
* the results it looks up */
+ set_bit(KEY_FLAG_ROOT_CAN_CLEAR, &keyring->flags);
cred->thread_keyring = keyring;
cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
dns_resolver_cache = cred;
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 0b3f5d72af1..6523599e9ac 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -388,11 +388,24 @@ long keyctl_keyring_clear(key_serial_t ringid)
keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_WRITE);
if (IS_ERR(keyring_ref)) {
ret = PTR_ERR(keyring_ref);
+
+ /* Root is permitted to invalidate certain special keyrings */
+ if (capable(CAP_SYS_ADMIN)) {
+ keyring_ref = lookup_user_key(ringid, 0, 0);
+ if (IS_ERR(keyring_ref))
+ goto error;
+ if (test_bit(KEY_FLAG_ROOT_CAN_CLEAR,
+ &key_ref_to_ptr(keyring_ref)->flags))
+ goto clear;
+ goto error_put;
+ }
+
goto error;
}
+clear:
ret = keyring_clear(key_ref_to_ptr(keyring_ref));
-
+error_put:
key_ref_put(keyring_ref);
error:
return ret;