[RFC PATCH 2/4] selinux: clarify task subjective and objective credentials
Paul Moore
paul at paul-moore.com
Fri Feb 19 23:29:11 UTC 2021
SELinux has a function, task_sid(), which returns the task's
objective credentials, but unfortunately is used in a few places
where the subjective task credentials should be used. Most notably
in the new security_task_getsecid_subj() LSM hook.
This patch fixes this and attempts to make things more obvious by
introducing a new function, task_sid_subj(), and renaming the
existing task_sid() function to task_sid_obj().
Signed-off-by: Paul Moore <paul at paul-moore.com>
---
security/selinux/hooks.c | 85 +++++++++++++++++++++++++++-------------------
1 file changed, 49 insertions(+), 36 deletions(-)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index f311541c4972e..1c53000d28e37 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -229,10 +229,23 @@ 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
*/
-static inline u32 task_sid(const struct task_struct *task)
+static inline u32 task_sid_obj(const struct task_struct *task)
{
u32 sid;
@@ -2034,11 +2047,8 @@ static inline u32 open_file_to_av(struct file *file)
static int selinux_binder_set_context_mgr(struct task_struct *mgr)
{
- u32 mysid = current_sid();
- u32 mgrsid = task_sid(mgr);
-
return avc_has_perm(&selinux_state,
- mysid, mgrsid, SECCLASS_BINDER,
+ current_sid(), task_sid_obj(mgr), SECCLASS_BINDER,
BINDER__SET_CONTEXT_MGR, NULL);
}
@@ -2046,8 +2056,8 @@ static int selinux_binder_transaction(struct task_struct *from,
struct task_struct *to)
{
u32 mysid = current_sid();
- u32 fromsid = task_sid(from);
- u32 tosid = task_sid(to);
+ u32 fromsid = task_sid_subj(from);
+ u32 tosid = task_sid_subj(to);
int rc;
if (mysid != fromsid) {
@@ -2066,11 +2076,9 @@ static int selinux_binder_transaction(struct task_struct *from,
static int selinux_binder_transfer_binder(struct task_struct *from,
struct task_struct *to)
{
- u32 fromsid = task_sid(from);
- u32 tosid = task_sid(to);
-
return avc_has_perm(&selinux_state,
- fromsid, tosid, SECCLASS_BINDER, BINDER__TRANSFER,
+ task_sid_subj(from), task_sid_obj(to),
+ SECCLASS_BINDER, BINDER__TRANSFER,
NULL);
}
@@ -2078,7 +2086,7 @@ static int selinux_binder_transfer_file(struct task_struct *from,
struct task_struct *to,
struct file *file)
{
- u32 sid = task_sid(to);
+ u32 sid = task_sid_subj(to);
struct file_security_struct *fsec = selinux_file(file);
struct dentry *dentry = file->f_path.dentry;
struct inode_security_struct *isec;
@@ -2114,10 +2122,10 @@ static int selinux_binder_transfer_file(struct task_struct *from,
}
static int selinux_ptrace_access_check(struct task_struct *child,
- unsigned int mode)
+ unsigned int mode)
{
u32 sid = current_sid();
- u32 csid = task_sid(child);
+ u32 csid = task_sid_obj(child);
if (mode & PTRACE_MODE_READ)
return avc_has_perm(&selinux_state,
@@ -2130,15 +2138,15 @@ static int selinux_ptrace_access_check(struct task_struct *child,
static int selinux_ptrace_traceme(struct task_struct *parent)
{
return avc_has_perm(&selinux_state,
- task_sid(parent), current_sid(), SECCLASS_PROCESS,
- PROCESS__PTRACE, NULL);
+ task_sid_subj(parent), task_sid_obj(current),
+ SECCLASS_PROCESS, PROCESS__PTRACE, NULL);
}
static int selinux_capget(struct task_struct *target, kernel_cap_t *effective,
kernel_cap_t *inheritable, kernel_cap_t *permitted)
{
return avc_has_perm(&selinux_state,
- current_sid(), task_sid(target), SECCLASS_PROCESS,
+ current_sid(), task_sid_obj(target), SECCLASS_PROCESS,
PROCESS__GETCAP, NULL);
}
@@ -2263,7 +2271,7 @@ static u32 ptrace_parent_sid(void)
rcu_read_lock();
tracer = ptrace_parent(current);
if (tracer)
- sid = task_sid(tracer);
+ sid = task_sid_obj(tracer);
rcu_read_unlock();
return sid;
@@ -3916,7 +3924,7 @@ static int selinux_file_send_sigiotask(struct task_struct *tsk,
struct fown_struct *fown, int signum)
{
struct file *file;
- u32 sid = task_sid(tsk);
+ u32 sid = task_sid_obj(tsk);
u32 perm;
struct file_security_struct *fsec;
@@ -4135,47 +4143,52 @@ static int selinux_kernel_load_data(enum kernel_load_data_id id, bool contents)
static int selinux_task_setpgid(struct task_struct *p, pid_t pgid)
{
return avc_has_perm(&selinux_state,
- current_sid(), task_sid(p), SECCLASS_PROCESS,
+ current_sid(), task_sid_obj(p), SECCLASS_PROCESS,
PROCESS__SETPGID, NULL);
}
static int selinux_task_getpgid(struct task_struct *p)
{
return avc_has_perm(&selinux_state,
- current_sid(), task_sid(p), SECCLASS_PROCESS,
+ current_sid(), task_sid_obj(p), SECCLASS_PROCESS,
PROCESS__GETPGID, NULL);
}
static int selinux_task_getsid(struct task_struct *p)
{
return avc_has_perm(&selinux_state,
- current_sid(), task_sid(p), SECCLASS_PROCESS,
+ current_sid(), task_sid_obj(p), SECCLASS_PROCESS,
PROCESS__GETSESSION, NULL);
}
-static void selinux_task_getsecid(struct task_struct *p, u32 *secid)
+static void selinux_task_getsecid_subj(struct task_struct *p, u32 *secid)
+{
+ *secid = task_sid_subj(p);
+}
+
+static void selinux_task_getsecid_obj(struct task_struct *p, u32 *secid)
{
- *secid = task_sid(p);
+ *secid = task_sid_obj(p);
}
static int selinux_task_setnice(struct task_struct *p, int nice)
{
return avc_has_perm(&selinux_state,
- current_sid(), task_sid(p), SECCLASS_PROCESS,
+ current_sid(), task_sid_obj(p), SECCLASS_PROCESS,
PROCESS__SETSCHED, NULL);
}
static int selinux_task_setioprio(struct task_struct *p, int ioprio)
{
return avc_has_perm(&selinux_state,
- current_sid(), task_sid(p), SECCLASS_PROCESS,
+ current_sid(), task_sid_obj(p), SECCLASS_PROCESS,
PROCESS__SETSCHED, NULL);
}
static int selinux_task_getioprio(struct task_struct *p)
{
return avc_has_perm(&selinux_state,
- current_sid(), task_sid(p), SECCLASS_PROCESS,
+ current_sid(), task_sid_obj(p), SECCLASS_PROCESS,
PROCESS__GETSCHED, NULL);
}
@@ -4206,7 +4219,7 @@ static int selinux_task_setrlimit(struct task_struct *p, unsigned int resource,
upon context transitions. See selinux_bprm_committing_creds. */
if (old_rlim->rlim_max != new_rlim->rlim_max)
return avc_has_perm(&selinux_state,
- current_sid(), task_sid(p),
+ current_sid(), task_sid_obj(p),
SECCLASS_PROCESS, PROCESS__SETRLIMIT, NULL);
return 0;
@@ -4215,21 +4228,21 @@ static int selinux_task_setrlimit(struct task_struct *p, unsigned int resource,
static int selinux_task_setscheduler(struct task_struct *p)
{
return avc_has_perm(&selinux_state,
- current_sid(), task_sid(p), SECCLASS_PROCESS,
+ current_sid(), task_sid_obj(p), SECCLASS_PROCESS,
PROCESS__SETSCHED, NULL);
}
static int selinux_task_getscheduler(struct task_struct *p)
{
return avc_has_perm(&selinux_state,
- current_sid(), task_sid(p), SECCLASS_PROCESS,
+ current_sid(), task_sid_obj(p), SECCLASS_PROCESS,
PROCESS__GETSCHED, NULL);
}
static int selinux_task_movememory(struct task_struct *p)
{
return avc_has_perm(&selinux_state,
- current_sid(), task_sid(p), SECCLASS_PROCESS,
+ current_sid(), task_sid_obj(p), SECCLASS_PROCESS,
PROCESS__SETSCHED, NULL);
}
@@ -4248,14 +4261,14 @@ static int selinux_task_kill(struct task_struct *p, struct kernel_siginfo *info,
else
secid = cred_sid(cred);
return avc_has_perm(&selinux_state,
- secid, task_sid(p), SECCLASS_PROCESS, perm, NULL);
+ secid, task_sid_obj(p), SECCLASS_PROCESS, perm, NULL);
}
static void selinux_task_to_inode(struct task_struct *p,
struct inode *inode)
{
struct inode_security_struct *isec = selinux_inode(inode);
- u32 sid = task_sid(p);
+ u32 sid = task_sid_obj(p);
spin_lock(&isec->lock);
isec->sclass = inode_mode_to_security_class(inode->i_mode);
@@ -6148,7 +6161,7 @@ static int selinux_msg_queue_msgrcv(struct kern_ipc_perm *msq, struct msg_msg *m
struct ipc_security_struct *isec;
struct msg_security_struct *msec;
struct common_audit_data ad;
- u32 sid = task_sid(target);
+ u32 sid = task_sid_subj(target);
int rc;
isec = selinux_ipc(msq);
@@ -7143,8 +7156,8 @@ 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),
- LSM_HOOK_INIT(task_getsecid_obj, selinux_task_getsecid),
+ LSM_HOOK_INIT(task_getsecid_subj, selinux_task_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),
LSM_HOOK_INIT(task_getioprio, selinux_task_getioprio),
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