[apparmor] [PATCH 4/5] Add the ability to read proc attr interfaces

[John Johansen]

Signed-off-by: John Johansen <john.johansen at canonical.com>
---
 libraries/libapparmor/src/kernel_interface.c |   56 ++++++++++++++++++++++++++
 1 files changed, 56 insertions(+), 0 deletions(-)

diff --git a/libraries/libapparmor/src/kernel_interface.c b/libraries/libapparmor/src/kernel_interface.c
index 4e6c1e9..8e275f2 100644
--- a/libraries/libapparmor/src/kernel_interface.c
+++ b/libraries/libapparmor/src/kernel_interface.c
@@ -54,6 +54,62 @@ static char *procattr_path(pid_t pid, const char *attr)
 	return NULL;
 }
 
+/**
+ * getprocattr - get the contents of @attr for @tid into @buf
+ * @tid: tid of task to query
+ * @attr: which /proc/<tid>/current/attr to query
+ * @buf: buffer to store the result in
+ * @len: size of the buffer
+ *
+ * Returns: size of data read or -1 on error, and sets errno
+ */
+static int getprocattr(pid_t tid, const char *attr, char *buf, int len)
+{
+	int rc = -1;
+	int fd, ret;
+	char *ctl = NULL;
+	int size = 0;
+
+	if (!buf) {
+		errno = EINVAL;
+		goto out;
+	}
+
+	ctl = procattr_path(tid, attr);
+	if (!ctl)
+		goto out;
+
+	fd = open(ctl, O_RDONLY);
+	if (fd == -1) {
+		goto out;
+	}
+
+	ret = 1;
+	for (ret = 1; ret > 0 && len > 0; buf += ret, len -= ret, size += ret) {
+		ret = read(fd, buf, len);
+	}
+
+	if (ret < 0) {
+		int saved;
+		if (ret != -1) {
+			errno = EPROTO;
+		}
+		saved = errno;
+		(void)close(fd);
+		errno = saved;
+		goto out;
+	}
+
+	(void)close(fd);
+
+	rc = size;
+out:
+	if (ctl) {
+		free(ctl);
+	}
+	return rc;
+}
+
 static int setprocattr(pid_t tid, const char *attr, const char *buf, int len)
 {
 	int rc = -1;
-- 
1.7.5.4