On Wed, Sep 29, 2021 at 3:17 PM Paul Moore <paul@xxxxxxxxxxxxxx> wrote:
>
> The security_task_getsecid_subj() LSM hook invites misuse by allowing
> callers to specify a task even though the hook is only safe when the
> current task is referenced. Fix this by removing the task_struct
> argument to the hook, requiring LSM implementations to use the
> current task. While we are changing the hook declaration we also
> rename the function to security_current_getsecid_subj() in an effort
> to reinforce that the hook captures the subjective credentials of the
> current task and not an arbitrary task on the system.
>
> Signed-off-by: Paul Moore <paul@xxxxxxxxxxxxxx>
> ---
> include/linux/lsm_hook_defs.h | 3 +--
> include/linux/lsm_hooks.h | 8 +++-----
> include/linux/security.h | 4 ++--
> kernel/audit.c | 4 ++--
> kernel/auditfilter.c | 3 +--
> kernel/auditsc.c | 10 +++++++++-
> net/netlabel/netlabel_unlabeled.c | 2 +-
> net/netlabel/netlabel_user.h | 2 +-
> security/apparmor/lsm.c | 13 ++++++++++---
> security/integrity/ima/ima_appraise.c | 2 +-
> security/integrity/ima/ima_main.c | 14 +++++++-------
> security/security.c | 6 +++---
> security/selinux/hooks.c | 19 +++----------------
> security/smack/smack.h | 16 ----------------
> security/smack/smack_lsm.c | 9 ++++-----
> 15 files changed, 48 insertions(+), 67 deletions(-)
I never saw any comments, positive or negative, on this patch so I'll
plan on merging it early next week. If you've got objections, now is
the time to speak up.
> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> index 2adeea44c0d5..8d04b18155a3 100644
> --- a/include/linux/lsm_hook_defs.h
> +++ b/include/linux/lsm_hook_defs.h
> @@ -205,8 +205,7 @@ LSM_HOOK(int, 0, task_fix_setgid, struct cred *new, const struct cred * old,
> LSM_HOOK(int, 0, task_setpgid, struct task_struct *p, pid_t pgid)
> LSM_HOOK(int, 0, task_getpgid, struct task_struct *p)
> LSM_HOOK(int, 0, task_getsid, struct task_struct *p)
> -LSM_HOOK(void, LSM_RET_VOID, task_getsecid_subj,
> - struct task_struct *p, u32 *secid)
> +LSM_HOOK(void, LSM_RET_VOID, current_getsecid_subj, u32 *secid)
> LSM_HOOK(void, LSM_RET_VOID, task_getsecid_obj,
> struct task_struct *p, u32 *secid)
> LSM_HOOK(int, 0, task_setnice, struct task_struct *p, int nice)
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index 5c4c5c0602cb..9f5b93011ecb 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -716,11 +716,9 @@
> * @p.
> * @p contains the task_struct for the process.
> * Return 0 if permission is granted.
> - * @task_getsecid_subj:
> - * Retrieve the subjective security identifier of the task_struct in @p
> - * and return it in @secid. Special care must be taken to ensure that @p
> - * is the either the "current" task, or the caller has exclusive access
> - * to @p.
> + * @current_getsecid_subj:
> + * Retrieve the subjective security identifier of the current task and
> + * return it in @secid.
> * In case of failure, @secid will be set to zero.
> * @task_getsecid_obj:
> * Retrieve the objective security identifier of the task_struct in @p
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 5b7288521300..24190cf61858 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -417,7 +417,7 @@ int security_task_fix_setgid(struct cred *new, const struct cred *old,
> int security_task_setpgid(struct task_struct *p, pid_t pgid);
> int security_task_getpgid(struct task_struct *p);
> int security_task_getsid(struct task_struct *p);
> -void security_task_getsecid_subj(struct task_struct *p, u32 *secid);
> +void security_current_getsecid_subj(u32 *secid);
> void security_task_getsecid_obj(struct task_struct *p, u32 *secid);
> int security_task_setnice(struct task_struct *p, int nice);
> int security_task_setioprio(struct task_struct *p, int ioprio);
> @@ -1112,7 +1112,7 @@ static inline int security_task_getsid(struct task_struct *p)
> return 0;
> }
>
> -static inline void security_task_getsecid_subj(struct task_struct *p, u32 *secid)
> +static inline void security_current_getsecid_subj(u32 *secid)
> {
> *secid = 0;
> }
> diff --git a/kernel/audit.c b/kernel/audit.c
> index 121d37e700a6..d4084751cfe6 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -2132,7 +2132,7 @@ int audit_log_task_context(struct audit_buffer *ab)
> int error;
> u32 sid;
>
> - security_task_getsecid_subj(current, &sid);
> + security_current_getsecid_subj(&sid);
> if (!sid)
> return 0;
>
> @@ -2353,7 +2353,7 @@ int audit_signal_info(int sig, struct task_struct *t)
> audit_sig_uid = auid;
> else
> audit_sig_uid = uid;
> - security_task_getsecid_subj(current, &audit_sig_sid);
> + security_current_getsecid_subj(&audit_sig_sid);
> }
>
> return audit_signal_info_syscall(t);
> diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
> index db2c6b59dfc3..f4ebd2f1cfca 100644
> --- a/kernel/auditfilter.c
> +++ b/kernel/auditfilter.c
> @@ -1359,8 +1359,7 @@ int audit_filter(int msgtype, unsigned int listtype)
> case AUDIT_SUBJ_SEN:
> case AUDIT_SUBJ_CLR:
> if (f->lsm_rule) {
> - security_task_getsecid_subj(current,
> - &sid);
> + security_current_getsecid_subj(&sid);
> result = security_audit_rule_match(sid,
> f->type, f->op, f->lsm_rule);
> }
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index 8dd73a64f921..e0987ee71b8f 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -673,7 +673,15 @@ static int audit_filter_rules(struct task_struct *tsk,
> logged upon error */
> if (f->lsm_rule) {
> if (need_sid) {
> - security_task_getsecid_subj(tsk, &sid);
> + /* @tsk should always be equal to
> + * @current with the exception of
> + * fork()/copy_process() in which case
> + * the new @tsk creds are still a dup
> + * of @current's creds so we can still
> + * use security_current_getsecid_subj()
> + * here even though it always refs
> + * @current's creds */
> + security_current_getsecid_subj(&sid);
> need_sid = 0;
> }
> result = security_audit_rule_match(sid, f->type,
> diff --git a/net/netlabel/netlabel_unlabeled.c b/net/netlabel/netlabel_unlabeled.c
> index 566ba4397ee4..8490e46359ae 100644
> --- a/net/netlabel/netlabel_unlabeled.c
> +++ b/net/netlabel/netlabel_unlabeled.c
> @@ -1537,7 +1537,7 @@ int __init netlbl_unlabel_defconf(void)
> /* Only the kernel is allowed to call this function and the only time
> * it is called is at bootup before the audit subsystem is reporting
> * messages so don't worry to much about these values. */
> - security_task_getsecid_subj(current, &audit_info.secid);
> + security_current_getsecid_subj(&audit_info.secid);
> audit_info.loginuid = GLOBAL_ROOT_UID;
> audit_info.sessionid = 0;
>
> diff --git a/net/netlabel/netlabel_user.h b/net/netlabel/netlabel_user.h
> index 6190cbf94bf0..d6c5b31eb4eb 100644
> --- a/net/netlabel/netlabel_user.h
> +++ b/net/netlabel/netlabel_user.h
> @@ -32,7 +32,7 @@
> */
> static inline void netlbl_netlink_auditinfo(struct netlbl_audit *audit_info)
> {
> - security_task_getsecid_subj(current, &audit_info->secid);
> + security_current_getsecid_subj(&audit_info->secid);
> audit_info->loginuid = audit_get_loginuid(current);
> audit_info->sessionid = audit_get_sessionid(current);
> }
> diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
> index f72406fe1bf2..fc21190c4f4f 100644
> --- a/security/apparmor/lsm.c
> +++ b/security/apparmor/lsm.c
> @@ -728,7 +728,14 @@ static void apparmor_bprm_committed_creds(struct linux_binprm *bprm)
> return;
> }
>
> -static void apparmor_task_getsecid(struct task_struct *p, u32 *secid)
> +static void apparmor_current_getsecid_subj(u32 *secid)
> +{
> + struct aa_label *label = aa_get_task_label(current);
> + *secid = label->secid;
> + aa_put_label(label);
> +}
> +
> +static void apparmor_task_getsecid_obj(struct task_struct *p, u32 *secid)
> {
> struct aa_label *label = aa_get_task_label(p);
> *secid = label->secid;
> @@ -1252,8 +1259,8 @@ static struct security_hook_list apparmor_hooks[] __lsm_ro_after_init = {
>
> LSM_HOOK_INIT(task_free, apparmor_task_free),
> LSM_HOOK_INIT(task_alloc, apparmor_task_alloc),
> - LSM_HOOK_INIT(task_getsecid_subj, apparmor_task_getsecid),
> - LSM_HOOK_INIT(task_getsecid_obj, apparmor_task_getsecid),
> + LSM_HOOK_INIT(current_getsecid_subj, apparmor_current_getsecid_subj),
> + LSM_HOOK_INIT(task_getsecid_obj, apparmor_task_getsecid_obj),
> LSM_HOOK_INIT(task_setrlimit, apparmor_task_setrlimit),
> LSM_HOOK_INIT(task_kill, apparmor_task_kill),
>
> diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
> index dbba51583e7c..17232bbfb9f9 100644
> --- a/security/integrity/ima/ima_appraise.c
> +++ b/security/integrity/ima/ima_appraise.c
> @@ -76,7 +76,7 @@ int ima_must_appraise(struct user_namespace *mnt_userns, struct inode *inode,
> if (!ima_appraise)
> return 0;
>
> - security_task_getsecid_subj(current, &secid);
> + security_current_getsecid_subj(&secid);
> return ima_match_policy(mnt_userns, inode, current_cred(), secid,
> func, mask, IMA_APPRAISE | IMA_HASH, NULL,
> NULL, NULL, NULL);
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index 465865412100..8c6e4514d494 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -408,7 +408,7 @@ int ima_file_mmap(struct file *file, unsigned long prot)
> u32 secid;
>
> if (file && (prot & PROT_EXEC)) {
> - security_task_getsecid_subj(current, &secid);
> + security_current_getsecid_subj(&secid);
> return process_measurement(file, current_cred(), secid, NULL,
> 0, MAY_EXEC, MMAP_CHECK);
> }
> @@ -446,7 +446,7 @@ int ima_file_mprotect(struct vm_area_struct *vma, unsigned long prot)
> !(prot & PROT_EXEC) || (vma->vm_flags & VM_EXEC))
> return 0;
>
> - security_task_getsecid_subj(current, &secid);
> + security_current_getsecid_subj(&secid);
> inode = file_inode(vma->vm_file);
> action = ima_get_action(file_mnt_user_ns(vma->vm_file), inode,
> current_cred(), secid, MAY_EXEC, MMAP_CHECK,
> @@ -487,7 +487,7 @@ int ima_bprm_check(struct linux_binprm *bprm)
> int ret;
> u32 secid;
>
> - security_task_getsecid_subj(current, &secid);
> + security_current_getsecid_subj(&secid);
> ret = process_measurement(bprm->file, current_cred(), secid, NULL, 0,
> MAY_EXEC, BPRM_CHECK);
> if (ret)
> @@ -512,7 +512,7 @@ int ima_file_check(struct file *file, int mask)
> {
> u32 secid;
>
> - security_task_getsecid_subj(current, &secid);
> + security_current_getsecid_subj(&secid);
> return process_measurement(file, current_cred(), secid, NULL, 0,
> mask & (MAY_READ | MAY_WRITE | MAY_EXEC |
> MAY_APPEND), FILE_CHECK);
> @@ -709,7 +709,7 @@ int ima_read_file(struct file *file, enum kernel_read_file_id read_id,
>
> /* Read entire file for all partial reads. */
> func = read_idmap[read_id] ?: FILE_CHECK;
> - security_task_getsecid_subj(current, &secid);
> + security_current_getsecid_subj(&secid);
> return process_measurement(file, current_cred(), secid, NULL,
> 0, MAY_READ, func);
> }
> @@ -752,7 +752,7 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size,
> }
>
> func = read_idmap[read_id] ?: FILE_CHECK;
> - security_task_getsecid_subj(current, &secid);
> + security_current_getsecid_subj(&secid);
> return process_measurement(file, current_cred(), secid, buf, size,
> MAY_READ, func);
> }
> @@ -905,7 +905,7 @@ int process_buffer_measurement(struct user_namespace *mnt_userns,
> * buffer measurements.
> */
> if (func) {
> - security_task_getsecid_subj(current, &secid);
> + security_current_getsecid_subj(&secid);
> action = ima_get_action(mnt_userns, inode, current_cred(),
> secid, 0, func, &pcr, &template,
> func_data, NULL);
> diff --git a/security/security.c b/security/security.c
> index 9ffa9e9c5c55..827bd161f8b0 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -1807,12 +1807,12 @@ int security_task_getsid(struct task_struct *p)
> return call_int_hook(task_getsid, 0, p);
> }
>
> -void security_task_getsecid_subj(struct task_struct *p, u32 *secid)
> +void security_current_getsecid_subj(u32 *secid)
> {
> *secid = 0;
> - call_void_hook(task_getsecid_subj, p, secid);
> + call_void_hook(current_getsecid_subj, secid);
> }
> -EXPORT_SYMBOL(security_task_getsecid_subj);
> +EXPORT_SYMBOL(security_current_getsecid_subj);
>
> void security_task_getsecid_obj(struct task_struct *p, u32 *secid)
> {
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index e7ebd45ca345..5c766b901f66 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -229,19 +229,6 @@ static inline u32 cred_sid(const struct cred *cred)
> return tsec->sid;
> }
>
> -/*
> - * get the subjective security ID of a task
> - */
> -static inline u32 task_sid_subj(const struct task_struct *task)
> -{
> - u32 sid;
> -
> - rcu_read_lock();
> - sid = cred_sid(rcu_dereference(task->cred));
> - rcu_read_unlock();
> - return sid;
> -}
> -
> /*
> * get the objective security ID of a task
> */
> @@ -4222,9 +4209,9 @@ static int selinux_task_getsid(struct task_struct *p)
> PROCESS__GETSESSION, NULL);
> }
>
> -static void selinux_task_getsecid_subj(struct task_struct *p, u32 *secid)
> +static void selinux_current_getsecid_subj(u32 *secid)
> {
> - *secid = task_sid_subj(p);
> + *secid = current_sid();
> }
>
> static void selinux_task_getsecid_obj(struct task_struct *p, u32 *secid)
> @@ -7221,7 +7208,7 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
> LSM_HOOK_INIT(task_setpgid, selinux_task_setpgid),
> LSM_HOOK_INIT(task_getpgid, selinux_task_getpgid),
> LSM_HOOK_INIT(task_getsid, selinux_task_getsid),
> - LSM_HOOK_INIT(task_getsecid_subj, selinux_task_getsecid_subj),
> + LSM_HOOK_INIT(current_getsecid_subj, selinux_current_getsecid_subj),
> LSM_HOOK_INIT(task_getsecid_obj, selinux_task_getsecid_obj),
> LSM_HOOK_INIT(task_setnice, selinux_task_setnice),
> LSM_HOOK_INIT(task_setioprio, selinux_task_setioprio),
> diff --git a/security/smack/smack.h b/security/smack/smack.h
> index 99c3422596ab..fc837dcebf96 100644
> --- a/security/smack/smack.h
> +++ b/security/smack/smack.h
> @@ -389,22 +389,6 @@ static inline struct smack_known *smk_of_task(const struct task_smack *tsp)
> return tsp->smk_task;
> }
>
> -static inline struct smack_known *smk_of_task_struct_subj(
> - const struct task_struct *t)
> -{
> - struct smack_known *skp;
> - const struct cred *cred;
> -
> - rcu_read_lock();
> -
> - cred = rcu_dereference(t->cred);
> - skp = smk_of_task(smack_cred(cred));
> -
> - rcu_read_unlock();
> -
> - return skp;
> -}
> -
> static inline struct smack_known *smk_of_task_struct_obj(
> const struct task_struct *t)
> {
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 21a0e7c3b8de..40e1d764e616 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -2061,15 +2061,14 @@ static int smack_task_getsid(struct task_struct *p)
> }
>
> /**
> - * smack_task_getsecid_subj - get the subjective secid of the task
> - * @p: the task
> + * smack_current_getsecid_subj - get the subjective secid of the current task
> * @secid: where to put the result
> *
> * Sets the secid to contain a u32 version of the task's subjective smack label.
> */
> -static void smack_task_getsecid_subj(struct task_struct *p, u32 *secid)
> +static void smack_current_getsecid_subj(u32 *secid)
> {
> - struct smack_known *skp = smk_of_task_struct_subj(p);
> + struct smack_known *skp = smk_of_current();
>
> *secid = skp->smk_secid;
> }
> @@ -4756,7 +4755,7 @@ static struct security_hook_list smack_hooks[] __lsm_ro_after_init = {
> LSM_HOOK_INIT(task_setpgid, smack_task_setpgid),
> LSM_HOOK_INIT(task_getpgid, smack_task_getpgid),
> LSM_HOOK_INIT(task_getsid, smack_task_getsid),
> - LSM_HOOK_INIT(task_getsecid_subj, smack_task_getsecid_subj),
> + LSM_HOOK_INIT(current_getsecid_subj, smack_current_getsecid_subj),
> LSM_HOOK_INIT(task_getsecid_obj, smack_task_getsecid_obj),
> LSM_HOOK_INIT(task_setnice, smack_task_setnice),
> LSM_HOOK_INIT(task_setioprio, smack_task_setioprio),
>
--
paul moore
www.paul-moore.com
