path: root/security/smack/smack_lsm.c
diff options
authorDavid Howells <>2008-11-14 10:39:28 +1100
committerJames Morris <>2008-11-14 10:39:28 +1100
commit3a3b7ce9336952ea7b9564d976d068a238976c9d (patch)
tree3f0a3be33022492161f534636a20a4b1059f8236 /security/smack/smack_lsm.c
parent1bfdc75ae077d60a01572a7781ec6264d55ab1b9 (diff)
CRED: Allow kernel services to override LSM settings for task actions
Allow kernel services to override LSM settings appropriate to the actions performed by a task by duplicating a set of credentials, modifying it and then using task_struct::cred to point to it when performing operations on behalf of a task. This is used, for example, by CacheFiles which has to transparently access the cache on behalf of a process that thinks it is doing, say, NFS accesses with a potentially inappropriate (with respect to accessing the cache) set of credentials. This patch provides two LSM hooks for modifying a task security record: (*) security_kernel_act_as() which allows modification of the security datum with which a task acts on other objects (most notably files). (*) security_kernel_create_files_as() which allows modification of the security datum that is used to initialise the security data on a file that a task creates. The patch also provides four new credentials handling functions, which wrap the LSM functions: (1) prepare_kernel_cred() Prepare a set of credentials for a kernel service to use, based either on a daemon's credentials or on init_cred. All the keyrings are cleared. (2) set_security_override() Set the LSM security ID in a set of credentials to a specific security context, assuming permission from the LSM policy. (3) set_security_override_from_ctx() As (2), but takes the security context as a string. (4) set_create_files_as() Set the file creation LSM security ID in a set of credentials to be the same as that on a particular inode. Signed-off-by: Casey Schaufler <> [Smack changes] Signed-off-by: David Howells <> Signed-off-by: James Morris <>
Diffstat (limited to 'security/smack/smack_lsm.c')
1 files changed, 37 insertions, 0 deletions
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index de396742abf4..8ad48161cef5 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -1012,6 +1012,41 @@ static void smack_cred_commit(struct cred *new, const struct cred *old)
+ * smack_kernel_act_as - Set the subjective context in a set of credentials
+ * @new points to the set of credentials to be modified.
+ * @secid specifies the security ID to be set
+ *
+ * Set the security data for a kernel service.
+ */
+static int smack_kernel_act_as(struct cred *new, u32 secid)
+ char *smack = smack_from_secid(secid);
+ if (smack == NULL)
+ return -EINVAL;
+ new->security = smack;
+ return 0;
+ * smack_kernel_create_files_as - Set the file creation label in a set of creds
+ * @new points to the set of credentials to be modified
+ * @inode points to the inode to use as a reference
+ *
+ * Set the file creation context in a set of credentials to the same
+ * as the objective context of the specified inode
+ */
+static int smack_kernel_create_files_as(struct cred *new,
+ struct inode *inode)
+ struct inode_smack *isp = inode->i_security;
+ new->security = isp->smk_inode;
+ return 0;
* smack_task_setpgid - Smack check on setting pgid
* @p: the task object
* @pgid: unused
@@ -2641,6 +2676,8 @@ struct security_operations smack_ops = {
.cred_free = smack_cred_free,
.cred_prepare = smack_cred_prepare,
.cred_commit = smack_cred_commit,
+ .kernel_act_as = smack_kernel_act_as,
+ .kernel_create_files_as = smack_kernel_create_files_as,
.task_fix_setuid = cap_task_fix_setuid,
.task_setpgid = smack_task_setpgid,
.task_getpgid = smack_task_getpgid,