Add file_ns_capable() helper function for open-time capability checking
Nothing is using it yet, but this will allow us to delay the open-time
checks to use time, without breaking the normal UNIX permission
semantics where permissions are determined by the opener (and the file
descriptor can then be passed to a different process, or the process can
drop capabilities).
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/capability.h b/include/linux/capability.h
index 98503b7..d9a4f7f 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -35,6 +35,7 @@
#define _KERNEL_CAP_T_SIZE (sizeof(kernel_cap_t))
+struct file;
struct inode;
struct dentry;
struct user_namespace;
@@ -211,6 +212,7 @@
extern bool ns_capable(struct user_namespace *ns, int cap);
extern bool nsown_capable(int cap);
extern bool inode_capable(const struct inode *inode, int cap);
+extern bool file_ns_capable(const struct file *file, struct user_namespace *ns, int cap);
/* audit system wants to get cap info from files as well */
extern int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps);
diff --git a/kernel/capability.c b/kernel/capability.c
index 493d972..f6c2ce5 100644
--- a/kernel/capability.c
+++ b/kernel/capability.c
@@ -393,6 +393,30 @@
EXPORT_SYMBOL(ns_capable);
/**
+ * file_ns_capable - Determine if the file's opener had a capability in effect
+ * @file: The file we want to check
+ * @ns: The usernamespace we want the capability in
+ * @cap: The capability to be tested for
+ *
+ * Return true if task that opened the file had a capability in effect
+ * when the file was opened.
+ *
+ * This does not set PF_SUPERPRIV because the caller may not
+ * actually be privileged.
+ */
+bool file_ns_capable(const struct file *file, struct user_namespace *ns, int cap)
+{
+ if (WARN_ON_ONCE(!cap_valid(cap)))
+ return false;
+
+ if (security_capable(file->f_cred, ns, cap) == 0)
+ return true;
+
+ return false;
+}
+EXPORT_SYMBOL(file_ns_capable);
+
+/**
* capable - Determine if the current task has a superior capability in effect
* @cap: The capability to be tested for
*
