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>

2 files changed, 37 insertions, 31 deletions

diff --git a/kernel/acct.c b/kernel/acct.c
index 5be01017d30f..08354195eecc 100644
--- a/kernel/acct.c
+++ b/kernel/acct.c
@@ -260,10 +260,10 @@ SYSCALL_DEFINE1(acct, const char __user *, name)
                 return -EPERM;
 
         if (name) {
-                char *tmp = getname(name);
+                struct filename *tmp = getname(name);
                 if (IS_ERR(tmp))
                         return (PTR_ERR(tmp));
-                error = acct_on(tmp);
+                error = acct_on(tmp->name);
                 putname(tmp);
         } else {
                 struct bsd_acct_struct *acct;
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index d147585e9ef3..d4d82319eed5 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)) {