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Message-ID: <4CDD4349.6090601@schaufler-ca.com>
Date: Fri, 12 Nov 2010 05:38:17 -0800
From: Casey Schaufler <casey@...aufler-ca.com>
To: Jarkko Sakkinen <jarkko.j.sakkinen@...il.com>
CC: linux-kernel@...r.kernel.org,
linux-security-module@...r.kernel.org,
Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH] Smack: label for task objects
On 11/11/2010 8:44 AM, Jarkko Sakkinen wrote:
> Applied against
> http://gitorious.org/simplified-mandatory-access-control-kernel
> 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.
The smk_task value needs to get reset if the SMACK64EXEC attribute
gets written. I have a fix that I am testing and will pass along
presently.
> Signed-off-by: Jarkko Sakkinen <jarkko.j.sakkinen@...il.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 a1bdbfa..14be2b2 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);
> @@ -1756,7 +1811,7 @@ 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;
> }
> @@ -1792,7 +1847,7 @@ 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;
> }
> @@ -1915,7 +1970,7 @@ 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;
> }
> @@ -2033,7 +2088,7 @@ 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;
> }
> @@ -2205,7 +2260,7 @@ 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;
> @@ -2325,9 +2380,13 @@ 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;
> }
> @@ -2362,7 +2421,7 @@ 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;
> @@ -2386,6 +2445,7 @@ 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;
> @@ -2418,7 +2478,13 @@ 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;
> }
> @@ -2719,7 +2785,7 @@ 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() */
> }
> @@ -2840,7 +2906,7 @@ 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;
> }
> @@ -2869,6 +2935,7 @@ 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)
> @@ -2882,14 +2949,14 @@ 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 */
> @@ -3091,6 +3158,8 @@ 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,
> @@ -3227,9 +3296,16 @@ 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");
> @@ -3237,7 +3313,9 @@ 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;
--
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