vfs: define struct filename and have getname() return it

getname() is intended to copy pathname strings from userspace into a
kernel buffer. The result is just a string in kernel space. It would
however be quite helpful to be able to attach some ancillary info to
the string.

For instance, we could attach some audit-related info to reduce the
amount of audit-related processing needed. When auditing is enabled,
we could also call getname() on the string more than once and not
need to recopy it from userspace.

This patchset converts the getname()/putname() interfaces to return
a struct instead of a string. For now, the struct just tracks the
string in kernel space and the original userland pointer for it.

Later, we'll add other information to the struct as it becomes
convenient.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 35 insertions, 29 deletions

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index d147585..d4d8231 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -103,28 +103,29 @@ struct audit_cap_data {
  * we don't let putname() free it (instead we free all of the saved
  * pointers at syscall exit time).
  *
- * Further, in fs/namei.c:path_lookup() we store the inode and device. */
+ * Further, in fs/namei.c:path_lookup() we store the inode and device.
+ */
 struct audit_names {
-	struct list_head list;		/* audit_context->names_list */
-	const char	*name;
-	unsigned long	ino;
-	dev_t		dev;
-	umode_t		mode;
-	kuid_t		uid;
-	kgid_t		gid;
-	dev_t		rdev;
-	u32		osid;
-	struct audit_cap_data fcap;
-	unsigned int	fcap_ver;
-	int		name_len;	/* number of name's characters to log */
-	unsigned char	type;		/* record type */
-	bool		name_put;	/* call __putname() for this name */
+	struct list_head	list;		/* audit_context->names_list */
+	struct filename	*name;
+	unsigned long		ino;
+	dev_t			dev;
+	umode_t			mode;
+	kuid_t			uid;
+	kgid_t			gid;
+	dev_t			rdev;
+	u32			osid;
+	struct audit_cap_data	 fcap;
+	unsigned int		fcap_ver;
+	int			name_len;	/* number of name's characters to log */
+	unsigned char		type;		/* record type */
+	bool			name_put;	/* call __putname() for this name */
 	/*
 	 * This was an allocated audit_names and not from the array of
 	 * names allocated in the task audit context.  Thus this name
 	 * should be freed on syscall exit
 	 */
-	bool		should_free;
+	bool			should_free;
 };
 
 struct audit_aux_data {
@@ -996,7 +997,7 @@ static inline void audit_free_names(struct audit_context *context)
 		       context->ino_count);
 		list_for_each_entry(n, &context->names_list, list) {
 			printk(KERN_ERR "names[%d] = %p = %s\n", i,
-			       n->name, n->name ?: "(null)");
+			       n->name, n->name->name ?: "(null)");
 		}
 		dump_stack();
 		return;
@@ -1553,7 +1554,7 @@ static void audit_log_name(struct audit_context *context, struct audit_names *n,
 		case AUDIT_NAME_FULL:
 			/* log the full path */
 			audit_log_format(ab, " name=");
-			audit_log_untrustedstring(ab, n->name);
+			audit_log_untrustedstring(ab, n->name->name);
 			break;
 		case 0:
 			/* name was specified as a relative path and the
@@ -1563,7 +1564,7 @@ static void audit_log_name(struct audit_context *context, struct audit_names *n,
 		default:
 			/* log the name's directory component */
 			audit_log_format(ab, " name=");
-			audit_log_n_untrustedstring(ab, n->name,
+			audit_log_n_untrustedstring(ab, n->name->name,
 						    n->name_len);
 		}
 	} else
@@ -2026,7 +2027,7 @@ static struct audit_names *audit_alloc_name(struct audit_context *context,
  * Add a name to the list of audit names for this context.
  * Called from fs/namei.c:getname().
  */
-void __audit_getname(const char *name)
+void __audit_getname(struct filename *name)
 {
 	struct audit_context *context = current->audit_context;
 	struct audit_names *n;
@@ -2040,6 +2041,11 @@ void __audit_getname(const char *name)
 		return;
 	}
 
+#if AUDIT_DEBUG
+	/* The filename _must_ have a populated ->name */
+	BUG_ON(!name->name);
+#endif
+
 	n = audit_alloc_name(context, AUDIT_TYPE_UNKNOWN);
 	if (!n)
 		return;
@@ -2059,7 +2065,7 @@ void __audit_getname(const char *name)
  * then we delay the putname until syscall exit.
  * Called from include/linux/fs.h:putname().
  */
-void audit_putname(const char *name)
+void audit_putname(struct filename *name)
 {
 	struct audit_context *context = current->audit_context;
 
@@ -2074,7 +2080,7 @@ void audit_putname(const char *name)
 
 			list_for_each_entry(n, &context->names_list, list)
 				printk(KERN_ERR "name[%d] = %p = %s\n", i,
-				       n->name, n->name ?: "(null)");
+				       n->name, n->name->name ?: "(null)");
 			}
 #endif
 		__putname(name);
@@ -2088,8 +2094,8 @@ void audit_putname(const char *name)
 			       " put_count=%d\n",
 			       __FILE__, __LINE__,
 			       context->serial, context->major,
-			       context->in_syscall, name, context->name_count,
-			       context->put_count);
+			       context->in_syscall, name->name,
+			       context->name_count, context->put_count);
 			dump_stack();
 		}
 	}
@@ -2152,7 +2158,7 @@ void __audit_inode(const char *name, const struct dentry *dentry,
 
 	list_for_each_entry_reverse(n, &context->names_list, list) {
 		/* does the name pointer match? */
-		if (n->name != name)
+		if (!n->name || n->name->name != name)
 			continue;
 
 		/* match the correct record type */
@@ -2175,7 +2181,7 @@ out_alloc:
 		return;
 out:
 	if (parent) {
-		n->name_len = n->name ? parent_len(n->name) : AUDIT_NAME_FULL;
+		n->name_len = n->name ? parent_len(n->name->name) : AUDIT_NAME_FULL;
 		n->type = AUDIT_TYPE_PARENT;
 	} else {
 		n->name_len = AUDIT_NAME_FULL;
@@ -2220,7 +2226,7 @@ void __audit_inode_child(const struct inode *parent,
 			continue;
 
 		if (n->ino == parent->i_ino &&
-		    !audit_compare_dname_path(dname, n->name, n->name_len)) {
+		    !audit_compare_dname_path(dname, n->name->name, n->name_len)) {
 			found_parent = n;
 			break;
 		}
@@ -2236,8 +2242,8 @@ void __audit_inode_child(const struct inode *parent,
 		if (found_parent && (n->name != found_parent->name))
 			continue;
 
-		if (!strcmp(dname, n->name) ||
-		    !audit_compare_dname_path(dname, n->name,
+		if (!strcmp(dname, n->name->name) ||
+		    !audit_compare_dname_path(dname, n->name->name,
 						found_parent ?
 						found_parent->name_len :
 						AUDIT_NAME_FULL)) {