Message-ID: <4CD39D96.3030609@nokia.com>
Date:	Fri, 05 Nov 2010 08:00:54 +0200
From:	Jarkko Sakkinen <ext-jarkko.2.sakkinen@...ia.com>
To:	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, casey@...aufler-ca.com
Subject: [PATCH] Smack: label for task objects (applies to 2.6.37-rc1)

This patch adds a new security attribute to Smack called
SMACK64EXEC. It defines label that is used while task is
running.

Exception: in smack_task_wait() child task is checked
for write access to parent task using label inherited
from the task that forked it.

Signed-off-by: Jarkko Sakkinen <ext-jarkko.2.sakkinen@...ia.com>
---
  include/linux/xattr.h         |    2 +
  security/smack/smack.h        |   30 +++++++
  security/smack/smack_access.c |    4 +-
  security/smack/smack_lsm.c    |  168 
++++++++++++++++++++++++++++++-----------
  security/smack/smackfs.c      |    4 +-
  5 files changed, 159 insertions(+), 49 deletions(-)

diff --git a/include/linux/xattr.h b/include/linux/xattr.h
index f1e5bde..351c790 100644
--- a/include/linux/xattr.h
+++ b/include/linux/xattr.h
@@ -40,9 +40,11 @@
  #define XATTR_SMACK_SUFFIX "SMACK64"
  #define XATTR_SMACK_IPIN "SMACK64IPIN"
  #define XATTR_SMACK_IPOUT "SMACK64IPOUT"
+#define XATTR_SMACK_EXEC "SMACK64EXEC"
  #define XATTR_NAME_SMACK XATTR_SECURITY_PREFIX XATTR_SMACK_SUFFIX
  #define XATTR_NAME_SMACKIPIN	XATTR_SECURITY_PREFIX XATTR_SMACK_IPIN
  #define XATTR_NAME_SMACKIPOUT	XATTR_SECURITY_PREFIX XATTR_SMACK_IPOUT
+#define XATTR_NAME_SMACKEXEC	XATTR_SECURITY_PREFIX XATTR_SMACK_EXEC
   #define XATTR_CAPS_SUFFIX "capability"
  #define XATTR_NAME_CAPS XATTR_SECURITY_PREFIX XATTR_CAPS_SUFFIX
diff --git a/security/smack/smack.h b/security/smack/smack.h
index 43ae747..a2e2cdf 100644
--- a/security/smack/smack.h
+++ b/security/smack/smack.h
@@ -51,10 +51,16 @@ struct socket_smack {
   */
  struct inode_smack {
  	char		*smk_inode;	/* label of the fso */
+	char		*smk_task;	/* label of the task */
  	struct mutex	smk_lock;	/* initialization lock */
  	int		smk_flags;	/* smack inode flags */
  };
  +struct task_smack {
+	char		*smk_task;	/* label used for access control */
+	char		*smk_forked;	/* label when forked */
+};
+
  #define	SMK_INODE_INSTANT	0x01	/* inode is instantiated */
   /*
@@ -243,6 +249,30 @@ static inline char *smk_of_inode(const struct inode 
*isp)
  }
   /*
+ * Present a pointer to the smack label in an task blob.
+ */
+static inline char *smk_of_task(const struct task_smack *tsp)
+{
+	return tsp->smk_task;
+}
+
+/*
+ * Present a pointer to the forked smack label in an task blob.
+ */
+static inline char *smk_of_forked(const struct task_smack *tsp)
+{
+	return tsp->smk_forked;
+}
+
+/*
+ * Present a pointer to the smack label in the curren task blob.
+ */
+static inline char *smk_of_current(void)
+{
+	return smk_of_task(current_security());
+}
+
+/*
   * logging functions
   */
  #define SMACK_AUDIT_DENIED 0x1
diff --git a/security/smack/smack_access.c b/security/smack/smack_access.c
index f4fac64..42becbc 100644
--- a/security/smack/smack_access.c
+++ b/security/smack/smack_access.c
@@ -185,7 +185,7 @@ out_audit:
  int smk_curacc(char *obj_label, u32 mode, struct smk_audit_info *a)
  {
  	int rc;
-	char *sp = current_security();
+	char *sp = smk_of_current();
   	rc = smk_access(sp, obj_label, mode, NULL);
  	if (rc == 0)
@@ -196,7 +196,7 @@ int smk_curacc(char *obj_label, u32 mode, struct 
smk_audit_info *a)
  	 * only one that gets privilege and current does not
  	 * have that label.
  	 */
-	if (smack_onlycap != NULL && smack_onlycap != current->cred->security)
+	if (smack_onlycap != NULL && smack_onlycap != sp)
  		goto out_audit;
   	if (capable(CAP_MAC_OVERRIDE))
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index bc39f40..e200cbb 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -43,7 +43,7 @@
   * Returns a pointer to the master list entry for the Smack label
   * or NULL if there was no label to fetch.
   */
-static char *smk_fetch(struct inode *ip, struct dentry *dp)
+static char *smk_fetch(const char *name, struct inode *ip, struct 
dentry *dp)
  {
  	int rc;
  	char in[SMK_LABELLEN];
@@ -51,7 +51,7 @@ static char *smk_fetch(struct inode *ip, struct dentry 
*dp)
  	if (ip->i_op->getxattr == NULL)
  		return NULL;
  -	rc = ip->i_op->getxattr(dp, XATTR_NAME_SMACK, in, SMK_LABELLEN);
+	rc = ip->i_op->getxattr(dp, name, in, SMK_LABELLEN);
  	if (rc < 0)
  		return NULL;
  @@ -103,8 +103,8 @@ static int smack_ptrace_access_check(struct 
task_struct *ctp, unsigned int mode)
  	if (rc != 0)
  		return rc;
  -	sp = current_security();
-	tsp = task_security(ctp);
+	sp = smk_of_current();
+	tsp = smk_of_task(task_security(ctp));
  	smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_TASK);
  	smk_ad_setfield_u_tsk(&ad, ctp);
  @@ -138,8 +138,8 @@ static int smack_ptrace_traceme(struct task_struct 
*ptp)
  	smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_TASK);
  	smk_ad_setfield_u_tsk(&ad, ptp);
  -	sp = current_security();
-	tsp = task_security(ptp);
+	sp = smk_of_current();
+	tsp = smk_of_task(task_security(ptp));
  	/* we won't log here, because rc can be overriden */
  	rc = smk_access(tsp, sp, MAY_READWRITE, NULL);
  	if (rc != 0 && has_capability(ptp, CAP_MAC_OVERRIDE))
@@ -160,7 +160,7 @@ static int smack_ptrace_traceme(struct task_struct *ptp)
  static int smack_syslog(int type, bool from_file)
  {
  	int rc;
-	char *sp = current_security();
+	char *sp = smk_of_current();
   	rc = cap_syslog(type, from_file);
  	if (rc != 0)
@@ -395,6 +395,40 @@ static int smack_sb_umount(struct vfsmount *mnt, 
int flags)
  }
   /*
+ * BPRM hooks
+ */
+
+static int smack_bprm_set_creds(struct linux_binprm *bprm)
+{
+	struct task_smack *tsp = bprm->cred->security;
+	struct inode_smack *isp;
+	struct dentry *dp;
+	int rc;
+
+	rc = cap_bprm_set_creds(bprm);
+	if (rc != 0)
+		return rc;
+
+	if (bprm->cred_prepared)
+		return 0;
+
+	if (bprm->file == NULL || bprm->file->f_dentry == NULL)
+		return 0;
+
+	dp = bprm->file->f_dentry;
+
+	if (dp->d_inode == NULL)
+		return 0;
+
+	isp = dp->d_inode->i_security;
+
+	if (isp->smk_task != NULL)
+		tsp->smk_task = isp->smk_task;
+
+	return 0;
+}
+
+/*
   * Inode hooks
   */
  @@ -406,7 +440,7 @@ static int smack_sb_umount(struct vfsmount *mnt, 
int flags)
   */
  static int smack_inode_alloc_security(struct inode *inode)
  {
-	inode->i_security = new_inode_smack(current_security());
+	inode->i_security = new_inode_smack(smk_of_current());
  	if (inode->i_security == NULL)
  		return -ENOMEM;
  	return 0;
@@ -668,7 +702,8 @@ static int smack_inode_setxattr(struct dentry 
*dentry, const char *name,
   	if (strcmp(name, XATTR_NAME_SMACK) == 0 ||
  	    strcmp(name, XATTR_NAME_SMACKIPIN) == 0 ||
-	    strcmp(name, XATTR_NAME_SMACKIPOUT) == 0) {
+	    strcmp(name, XATTR_NAME_SMACKIPOUT) == 0 ||
+	    strcmp(name, XATTR_NAME_SMACKEXEC) == 0) {
  		if (!capable(CAP_MAC_ADMIN))
  			rc = -EPERM;
  		/*
@@ -761,7 +796,8 @@ static int smack_inode_removexattr(struct dentry 
*dentry, const char *name)
   	if (strcmp(name, XATTR_NAME_SMACK) == 0 ||
  	    strcmp(name, XATTR_NAME_SMACKIPIN) == 0 ||
-	    strcmp(name, XATTR_NAME_SMACKIPOUT) == 0) {
+	    strcmp(name, XATTR_NAME_SMACKIPOUT) == 0 ||
+	    strcmp(name, XATTR_NAME_SMACKEXEC) == 0) {
  		if (!capable(CAP_MAC_ADMIN))
  			rc = -EPERM;
  	} else
@@ -899,7 +935,7 @@ static int smack_file_permission(struct file *file, 
int mask)
   */
  static int smack_file_alloc_security(struct file *file)
  {
-	file->f_security = current_security();
+	file->f_security = smk_of_current();
  	return 0;
  }
  @@ -1009,7 +1045,7 @@ static int smack_file_fcntl(struct file *file, 
unsigned int cmd,
   */
  static int smack_file_set_fowner(struct file *file)
  {
-	file->f_security = current_security();
+	file->f_security = smk_of_current();
  	return 0;
  }
  @@ -1029,7 +1065,7 @@ static int smack_file_send_sigiotask(struct 
task_struct *tsk,
  {
  	struct file *file;
  	int rc;
-	char *tsp = tsk->cred->security;
+	char *tsp = smk_of_task(tsk->cred->security);
  	struct smk_audit_info ad;
   	/*
@@ -1086,7 +1122,9 @@ static int smack_file_receive(struct file *file)
   */
  static int smack_cred_alloc_blank(struct cred *cred, gfp_t gfp)
  {
-	cred->security = NULL;
+	cred->security = kzalloc(sizeof(struct task_smack), gfp);
+	if (cred->security == NULL)
+		return -ENOMEM;
  	return 0;
  }
  @@ -1101,7 +1139,7 @@ static int smack_cred_alloc_blank(struct cred 
*cred, gfp_t gfp)
   */
  static void smack_cred_free(struct cred *cred)
  {
-	cred->security = NULL;
+	kfree(cred->security);
  }
   /**
@@ -1115,7 +1153,16 @@ static void smack_cred_free(struct cred *cred)
  static int smack_cred_prepare(struct cred *new, const struct cred *old,
  			      gfp_t gfp)
  {
-	new->security = old->security;
+	struct task_smack *old_tsp = old->security;
+	struct task_smack *new_tsp;
+
+	new_tsp = kzalloc(sizeof(struct task_smack), gfp);
+	if (new_tsp == NULL)
+		return -ENOMEM;
+
+	new_tsp->smk_task = old_tsp->smk_task;
+	new_tsp->smk_forked = old_tsp->smk_task;
+	new->security = new_tsp;
  	return 0;
  }
  @@ -1128,7 +1175,11 @@ static int smack_cred_prepare(struct cred *new, 
const struct cred *old,
   */
  static void smack_cred_transfer(struct cred *new, const struct cred *old)
  {
-	new->security = old->security;
+	struct task_smack *old_tsp = old->security;
+	struct task_smack *new_tsp = new->security;
+
+	new_tsp->smk_task = old_tsp->smk_task;
+	new_tsp->smk_forked = old_tsp->smk_task;
  }
   /**
@@ -1140,12 +1191,13 @@ static void smack_cred_transfer(struct cred 
*new, const struct cred *old)
   */
  static int smack_kernel_act_as(struct cred *new, u32 secid)
  {
+	struct task_smack *new_tsp = new->security;
  	char *smack = smack_from_secid(secid);
   	if (smack == NULL)
  		return -EINVAL;
  -	new->security = smack;
+	new_tsp->smk_task = smack;
  	return 0;
  }
  @@ -1161,8 +1213,10 @@ static int smack_kernel_create_files_as(struct 
cred *new,
  					struct inode *inode)
  {
  	struct inode_smack *isp = inode->i_security;
+	struct task_smack *tsp = new->security;
  -	new->security = isp->smk_inode;
+	tsp->smk_forked = isp->smk_inode;
+	tsp->smk_task = isp->smk_inode;
  	return 0;
  }
  @@ -1179,7 +1233,7 @@ static int smk_curacc_on_task(struct task_struct 
*p, int access)
   	smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_TASK);
  	smk_ad_setfield_u_tsk(&ad, p);
-	return smk_curacc(task_security(p), access, &ad);
+	return smk_curacc(smk_of_task(task_security(p)), access, &ad);
  }
   /**
@@ -1225,7 +1279,7 @@ static int smack_task_getsid(struct task_struct *p)
   */
  static void smack_task_getsecid(struct task_struct *p, u32 *secid)
  {
-	*secid = smack_to_secid(task_security(p));
+	*secid = smack_to_secid(smk_of_task(task_security(p)));
  }
   /**
@@ -1337,14 +1391,15 @@ static int smack_task_kill(struct task_struct 
*p, struct siginfo *info,
  	 * can write the receiver.
  	 */
  	if (secid == 0)
-		return smk_curacc(task_security(p), MAY_WRITE, &ad);
+		return smk_curacc(smk_of_task(task_security(p)), MAY_WRITE,
+				  &ad);
  	/*
  	 * If the secid isn't 0 we're dealing with some USB IO
  	 * specific behavior. This is not clean. For one thing
  	 * we can't take privilege into account.
  	 */
-	return smk_access(smack_from_secid(secid), task_security(p),
-			  MAY_WRITE, &ad);
+	return smk_access(smack_from_secid(secid),
+			  smk_of_task(task_security(p)), MAY_WRITE, &ad);
  }
   /**
@@ -1356,12 +1411,12 @@ static int smack_task_kill(struct task_struct 
*p, struct siginfo *info,
  static int smack_task_wait(struct task_struct *p)
  {
  	struct smk_audit_info ad;
-	char *sp = current_security();
-	char *tsp = task_security(p);
+	char *sp = smk_of_current();
+	char *tsp = smk_of_forked(task_security(p));
  	int rc;
   	/* we don't log here, we can be overriden */
-	rc = smk_access(sp, tsp, MAY_WRITE, NULL);
+	rc = smk_access(tsp, sp, MAY_WRITE, NULL);
  	if (rc == 0)
  		goto out_log;
  @@ -1382,7 +1437,7 @@ static int smack_task_wait(struct task_struct *p)
   out_log:
  	smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_TASK);
  	smk_ad_setfield_u_tsk(&ad, p);
-	smack_log(sp, tsp, MAY_WRITE, rc, &ad);
+	smack_log(tsp, sp, MAY_WRITE, rc, &ad);
  	return rc;
  }
  @@ -1396,7 +1451,7 @@ static int smack_task_wait(struct task_struct *p)
  static void smack_task_to_inode(struct task_struct *p, struct inode 
*inode)
  {
  	struct inode_smack *isp = inode->i_security;
-	isp->smk_inode = task_security(p);
+	isp->smk_inode = smk_of_task(task_security(p));
  }
   /*
@@ -1415,7 +1470,7 @@ static void smack_task_to_inode(struct task_struct 
*p, struct inode *inode)
   */
  static int smack_sk_alloc_security(struct sock *sk, int family, gfp_t 
gfp_flags)
  {
-	char *csp = current_security();
+	char *csp = smk_of_current();
  	struct socket_smack *ssp;
   	ssp = kzalloc(sizeof(struct socket_smack), gfp_flags);
@@ -1753,7 +1808,7 @@ static int smack_flags_to_may(int flags)
   */
  static int smack_msg_msg_alloc_security(struct msg_msg *msg)
  {
-	msg->security = current_security();
+	msg->security = smk_of_current();
  	return 0;
  }
  @@ -1789,7 +1844,7 @@ static int smack_shm_alloc_security(struct 
shmid_kernel *shp)
  {
  	struct kern_ipc_perm *isp = &shp->shm_perm;
  -	isp->security = current_security();
+	isp->security = smk_of_current();
  	return 0;
  }
  @@ -1912,7 +1967,7 @@ static int smack_sem_alloc_security(struct 
sem_array *sma)
  {
  	struct kern_ipc_perm *isp = &sma->sem_perm;
  -	isp->security = current_security();
+	isp->security = smk_of_current();
  	return 0;
  }
  @@ -2030,7 +2085,7 @@ static int smack_msg_queue_alloc_security(struct 
msg_queue *msq)
  {
  	struct kern_ipc_perm *kisp = &msq->q_perm;
  -	kisp->security = current_security();
+	kisp->security = smk_of_current();
  	return 0;
  }
  @@ -2202,7 +2257,7 @@ static void smack_d_instantiate(struct dentry 
*opt_dentry, struct inode *inode)
  	struct super_block *sbp;
  	struct superblock_smack *sbsp;
  	struct inode_smack *isp;
-	char *csp = current_security();
+	char *csp = smk_of_current();
  	char *fetched;
  	char *final;
  	struct dentry *dp;
@@ -2312,9 +2367,13 @@ static void smack_d_instantiate(struct dentry 
*opt_dentry, struct inode *inode)
  		 * Get the dentry for xattr.
  		 */
  		dp = dget(opt_dentry);
-		fetched = smk_fetch(inode, dp);
-		if (fetched != NULL)
+		fetched = smk_fetch(XATTR_NAME_SMACK, inode, dp);
+		if (fetched != NULL) {
  			final = fetched;
+			isp->smk_task = smk_fetch(XATTR_NAME_SMACKEXEC, inode,
+						  dp);
+		}
+
  		dput(dp);
  		break;
  	}
@@ -2349,7 +2408,7 @@ static int smack_getprocattr(struct task_struct 
*p, char *name, char **value)
  	if (strcmp(name, "current") != 0)
  		return -EINVAL;
  -	cp = kstrdup(task_security(p), GFP_KERNEL);
+	cp = kstrdup(smk_of_task(task_security(p)), GFP_KERNEL);
  	if (cp == NULL)
  		return -ENOMEM;
  @@ -2373,6 +2432,7 @@ static int smack_getprocattr(struct task_struct 
*p, char *name, char **value)
  static int smack_setprocattr(struct task_struct *p, char *name,
  			     void *value, size_t size)
  {
+	struct task_smack *tsp;
  	struct cred *new;
  	char *newsmack;
  @@ -2405,7 +2465,13 @@ static int smack_setprocattr(struct task_struct 
*p, char *name,
  	new = prepare_creds();
  	if (new == NULL)
  		return -ENOMEM;
-	new->security = newsmack;
+	tsp = kzalloc(sizeof(struct task_smack), GFP_KERNEL);
+	if (tsp == NULL) {
+		kfree(new);
+		return -ENOMEM;
+	}
+	tsp->smk_task = newsmack;
+	new->security = tsp;
  	commit_creds(new);
  	return size;
  }
@@ -2699,7 +2765,7 @@ static void smack_sock_graft(struct sock *sk, 
struct socket *parent)
  		return;
   	ssp = sk->sk_security;
-	ssp->smk_in = ssp->smk_out = current_security();
+	ssp->smk_in = ssp->smk_out = smk_of_current();
  	/* cssp->smk_packet is already set in smack_inet_csk_clone() */
  }
  @@ -2820,7 +2886,7 @@ static void smack_inet_csk_clone(struct sock *sk,
  static int smack_key_alloc(struct key *key, const struct cred *cred,
  			   unsigned long flags)
  {
-	key->security = cred->security;
+	key->security = smk_of_task(cred->security);
  	return 0;
  }
  @@ -2849,6 +2915,7 @@ static int smack_key_permission(key_ref_t key_ref,
  {
  	struct key *keyp;
  	struct smk_audit_info ad;
+	char *tsp = smk_of_task(cred->security);
   	keyp = key_ref_to_ptr(key_ref);
  	if (keyp == NULL)
@@ -2862,14 +2929,14 @@ static int smack_key_permission(key_ref_t key_ref,
  	/*
  	 * This should not occur
  	 */
-	if (cred->security == NULL)
+	if (tsp == NULL)
  		return -EACCES;
  #ifdef CONFIG_AUDIT
  	smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_KEY);
  	ad.a.u.key_struct.key = keyp->serial;
  	ad.a.u.key_struct.key_desc = keyp->description;
  #endif
-	return smk_access(cred->security, keyp->security,
+	return smk_access(tsp, keyp->security,
  				 MAY_READWRITE, &ad);
  }
  #endif /* CONFIG_KEYS */
@@ -3071,6 +3138,8 @@ struct security_operations smack_ops = {
  	.sb_mount = 			smack_sb_mount,
  	.sb_umount = 			smack_sb_umount,
  +	.bprm_set_creds =		smack_bprm_set_creds,
+
  	.inode_alloc_security = 	smack_inode_alloc_security,
  	.inode_free_security = 		smack_inode_free_security,
  	.inode_init_security = 		smack_inode_init_security,
@@ -3207,9 +3276,16 @@ static __init void init_smack_know_list(void)
  static __init int smack_init(void)
  {
  	struct cred *cred;
+	struct task_smack *tsp;
+
+	tsp = kzalloc(sizeof(struct task_smack), GFP_KERNEL);
+	if (tsp == NULL)
+		return -ENOMEM;
  -	if (!security_module_enable(&smack_ops))
+	if (!security_module_enable(&smack_ops)) {
+		kfree(tsp);
  		return 0;
+	}
   	printk(KERN_INFO "Smack:  Initializing.\n");
  @@ -3217,7 +3293,9 @@ static __init int smack_init(void)
  	 * Set the security state for the initial task.
  	 */
  	cred = (struct cred *) current->cred;
-	cred->security = &smack_known_floor.smk_known;
+	tsp->smk_forked = smack_known_floor.smk_known;
+	tsp->smk_task = smack_known_floor.smk_known;
+	cred->security = tsp;
   	/* initialize the smack_know_list */
  	init_smack_know_list();
diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
index dc1fd62..01a0be9 100644
--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -121,7 +121,7 @@ static void smk_netlabel_audit_set(struct 
netlbl_audit *nap)
  {
  	nap->loginuid = audit_get_loginuid(current);
  	nap->sessionid = audit_get_sessionid(current);
-	nap->secid = smack_to_secid(current_security());
+	nap->secid = smack_to_secid(smk_of_current());
  }
   /*
@@ -1160,7 +1160,7 @@ static ssize_t smk_write_onlycap(struct file 
*file, const char __user *buf,
  				 size_t count, loff_t *ppos)
  {
  	char in[SMK_LABELLEN];
-	char *sp = current->cred->security;
+	char *sp = smk_of_task(current->cred->security);
   	if (!capable(CAP_MAC_ADMIN))
  		return -EPERM;
-- 
1.7.1

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