[PATCH ghak90 V7 21/21] audit: add proc interface for capcontid

[Richard Guy Briggs]

Add a /proc interface to capcontid for testing purposes.  This isn't
intended to be merged upstream.  Container orchestrators/engines are
expected to link to libaudit to use the functions audit_set_capcontid()
and audit_get_capcontid.

Signed-off-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
---
 fs/proc/base.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 26091800180c..283ef8e006e7 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1360,6 +1360,59 @@ static ssize_t proc_contid_write(struct file *file, const char __user *buf,
 	.write		= proc_contid_write,
 	.llseek		= generic_file_llseek,
 };
+
+static ssize_t proc_capcontid_read(struct file *file, char __user *buf,
+				  size_t count, loff_t *ppos)
+{
+	struct inode *inode = file_inode(file);
+	struct task_struct *task = get_proc_task(inode);
+	ssize_t length;
+	char tmpbuf[TMPBUFLEN];
+
+	if (!task)
+		return -ESRCH;
+	/* if we don't have caps, reject */
+	if (!capable(CAP_AUDIT_CONTROL) && !audit_get_capcontid(current))
+		return -EPERM;
+	length = scnprintf(tmpbuf, TMPBUFLEN, "%u", audit_get_capcontid(task));
+	put_task_struct(task);
+	return simple_read_from_buffer(buf, count, ppos, tmpbuf, length);
+}
+
+static ssize_t proc_capcontid_write(struct file *file, const char __user *buf,
+				   size_t count, loff_t *ppos)
+{
+	struct inode *inode = file_inode(file);
+	u32 capcontid;
+	int rv;
+	struct task_struct *task = get_proc_task(inode);
+
+	if (!task)
+		return -ESRCH;
+	if (*ppos != 0) {
+		/* No partial writes. */
+		put_task_struct(task);
+		return -EINVAL;
+	}
+
+	rv = kstrtou32_from_user(buf, count, 10, &capcontid);
+	if (rv < 0) {
+		put_task_struct(task);
+		return rv;
+	}
+
+	rv = audit_set_capcontid(task, capcontid);
+	put_task_struct(task);
+	if (rv < 0)
+		return rv;
+	return count;
+}
+
+static const struct file_operations proc_capcontid_operations = {
+	.read		= proc_capcontid_read,
+	.write		= proc_capcontid_write,
+	.llseek		= generic_file_llseek,
+};
 #endif
 
 #ifdef CONFIG_FAULT_INJECTION
@@ -3121,6 +3174,7 @@ static int proc_stack_depth(struct seq_file *m, struct pid_namespace *ns,
 	REG("loginuid",   S_IWUSR|S_IRUGO, proc_loginuid_operations),
 	REG("sessionid",  S_IRUGO, proc_sessionid_operations),
 	REG("audit_containerid", S_IWUSR|S_IRUSR, proc_contid_operations),
+	REG("audit_capcontainerid", S_IWUSR|S_IRUSR|S_IRUSR, proc_capcontid_operations),
 #endif
 #ifdef CONFIG_FAULT_INJECTION
 	REG("make-it-fail", S_IRUGO|S_IWUSR, proc_fault_inject_operations),
@@ -3522,6 +3576,7 @@ static int proc_tid_comm_permission(struct inode *inode, int mask)
 	REG("loginuid",  S_IWUSR|S_IRUGO, proc_loginuid_operations),
 	REG("sessionid",  S_IRUGO, proc_sessionid_operations),
 	REG("audit_containerid", S_IWUSR|S_IRUSR, proc_contid_operations),
+	REG("audit_capcontainerid", S_IWUSR|S_IRUSR|S_IRUSR, proc_capcontid_operations),
 #endif
 #ifdef CONFIG_FAULT_INJECTION
 	REG("make-it-fail", S_IRUGO|S_IWUSR, proc_fault_inject_operations),
-- 
1.8.3.1