[RFC PATCH v4 2/2] security/inode.c: Add capabilities file.

From: Francis Laniel
Date: Mon Jul 25 2022 - 08:42:27 EST


This new read-only file prints the capabilities values with their names:
cat /sys/kernel/security/capabilities
0 CAP_CHOWN
1 CAP_DAC_OVERRIDE
...
40 CAP_CHECKPOINT_RESTORE

Acked-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
Signed-off-by: Francis Laniel <flaniel@xxxxxxxxxxxxxxxxxxx>
---
security/inode.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

diff --git a/security/inode.c b/security/inode.c
index 6c326939750d..6da87ae5a8d6 100644
--- a/security/inode.c
+++ b/security/inode.c
@@ -21,6 +21,7 @@
#include <linux/security.h>
#include <linux/lsm_hooks.h>
#include <linux/magic.h>
+#include <linux/capability.h>

static struct vfsmount *mount;
static int mount_count;
@@ -328,6 +329,19 @@ static const struct file_operations lsm_ops = {
};
#endif

+static struct dentry *capabilities_dentry;
+static ssize_t capabilities_read(struct file *unused, char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ return simple_read_from_buffer(buf, count, ppos, cap_string,
+ strlen(cap_string));
+}
+
+static const struct file_operations capabilities_ops = {
+ .read = capabilities_read,
+ .llseek = generic_file_llseek,
+};
+
static int __init securityfs_init(void)
{
int retval;
@@ -345,6 +359,8 @@ static int __init securityfs_init(void)
lsm_dentry = securityfs_create_file("lsm", 0444, NULL, NULL,
&lsm_ops);
#endif
+ capabilities_dentry = securityfs_create_file("capabilities", 0444, NULL,
+ NULL, &capabilities_ops);
return 0;
}
core_initcall(securityfs_init);
--
2.25.1