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authorDavid Howells <dhowells@redhat.com>2008-11-14 10:39:19 +1100
committerJames Morris <jmorris@namei.org>2008-11-14 10:39:19 +1100
commitc69e8d9c01db2adc503464993c358901c9af9de4 (patch)
treebed94aaa9aeb7a7834d1c880f72b62a11a752c78 /security/keys/permission.c
parent86a264abe542cfececb4df129bc45a0338d8cdb9 (diff)
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CRED: Use RCU to access another task's creds and to release a task's own creds
Use RCU to access another task's creds and to release a task's own creds. This means that it will be possible for the credentials of a task to be replaced without another task (a) requiring a full lock to read them, and (b) seeing deallocated memory. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: James Morris <jmorris@namei.org> Acked-by: Serge Hallyn <serue@us.ibm.com> Signed-off-by: James Morris <jmorris@namei.org>
Diffstat (limited to 'security/keys/permission.c')
-rw-r--r--security/keys/permission.c10
1 files changed, 6 insertions, 4 deletions
diff --git a/security/keys/permission.c b/security/keys/permission.c
index baf3d5f31e7..13c36164f28 100644
--- a/security/keys/permission.c
+++ b/security/keys/permission.c
@@ -22,13 +22,16 @@ int key_task_permission(const key_ref_t key_ref,
struct task_struct *context,
key_perm_t perm)
{
- struct cred *cred = context->cred;
+ const struct cred *cred;
struct key *key;
key_perm_t kperm;
int ret;
key = key_ref_to_ptr(key_ref);
+ rcu_read_lock();
+ cred = __task_cred(context);
+
/* use the second 8-bits of permissions for keys the caller owns */
if (key->uid == cred->fsuid) {
kperm = key->perm >> 16;
@@ -43,10 +46,7 @@ int key_task_permission(const key_ref_t key_ref,
goto use_these_perms;
}
- spin_lock(&cred->lock);
ret = groups_search(cred->group_info, key->gid);
- spin_unlock(&cred->lock);
-
if (ret) {
kperm = key->perm >> 8;
goto use_these_perms;
@@ -57,6 +57,8 @@ int key_task_permission(const key_ref_t key_ref,
kperm = key->perm;
use_these_perms:
+ rcu_read_lock();
+
/* use the top 8-bits of permissions for keys the caller possesses
* - possessor permissions are additive with other permissions
*/