[PATCH 26/27] LSM: Add /proc attr entry for full LSM context

[Casey Schaufler <casey@xxxxxxxxxxxxxxxx>]

Add an entry /proc/.../attr/context which displays the full
process security "context" in compound format:'
	lsm1\0value\0lsm2\0value\0...
This entry is not writable.

Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
---
 fs/proc/base.c      |  1 +
 security/security.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 7bf70e041315..79600df5f7a2 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2619,6 +2619,7 @@ static const struct pid_entry attr_dir_stuff[] = {
 	ATTR(NULL, "keycreate",		0666),
 	ATTR(NULL, "sockcreate",	0666),
 	ATTR(NULL, "display",		0666),
+	ATTR(NULL, "context",		0666),
 #ifdef CONFIG_SECURITY_SMACK
 	DIR("smack",			0555,
 	    proc_smack_attr_dir_inode_ops, proc_smack_attr_dir_ops),
diff --git a/security/security.c b/security/security.c
index 5551c146c035..6a89a6b90cce 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2057,6 +2057,14 @@ int security_getprocattr(struct task_struct *p, const char *lsm, char *name,
 				char **value)
 {
 	struct security_hook_list *hp;
+	char *final = NULL;
+	char *cp;
+	char *tp;
+	int rc = 0;
+	int finallen = 0;
+	int llen;
+	int clen;
+	int tlen;
 	int display = lsm_task_display(current);
 	int slot = 0;
 
@@ -2074,6 +2082,43 @@ int security_getprocattr(struct task_struct *p, const char *lsm, char *name,
 		return -ENOMEM;
 	}
 
+	if (!strcmp(name, "context")) {
+		hlist_for_each_entry(hp, &security_hook_heads.getprocattr,
+				     list) {
+			rc = hp->hook.getprocattr(p, "current", &cp);
+			if (rc == -EINVAL || rc == -ENOPROTOOPT)
+				continue;
+			if (rc < 0) {
+				kfree(final);
+				return rc;
+			}
+			llen = strlen(hp->lsmid->lsm) + 1;
+			clen = strlen(cp) + 1;
+			tlen = llen + clen;
+			if (final)
+				tlen += finallen;
+			tp = kzalloc(tlen, GFP_KERNEL);
+			if (tp == NULL) {
+				kfree(cp);
+				kfree(final);
+				return -ENOMEM;
+			}
+			if (final)
+				memcpy(tp, final, finallen);
+			memcpy(tp + finallen, hp->lsmid->lsm, llen);
+			memcpy(tp + finallen + llen, cp, clen);
+			kfree(cp);
+			if (final)
+				kfree(final);
+			final = tp;
+			finallen = tlen;
+		}
+		if (final == NULL)
+			return -EINVAL;
+		*value = final;
+		return finallen;
+	}
+
 	hlist_for_each_entry(hp, &security_hook_heads.getprocattr, list) {
 		if (lsm != NULL && strcmp(lsm, hp->lsmid->lsm))
 			continue;
-- 
2.20.1