audit: optimize audit_compare_dname_path

In the cases where we already know the length of the parent, pass it as
a parm so we don't need to recompute it. In the cases where we don't
know the length, pass in AUDIT_NAME_FULL (-1) to indicate that it should
be determined.

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

4 files changed, 20 insertions, 12 deletions

diff --git a/kernel/audit.h b/kernel/audit.h
index 1038e23eb61c..d51cba868e1b 100644
--- a/kernel/audit.h
+++ b/kernel/audit.h
@@ -74,12 +74,15 @@ static inline int audit_hash_ino(u32 ino)
         return (ino & (AUDIT_INODE_BUCKETS-1));
 }
 
+/* Indicates that audit should log the full pathname. */
+#define AUDIT_NAME_FULL -1
+
 extern int audit_match_class(int class, unsigned syscall);
 extern int audit_comparator(const u32 left, const u32 op, const u32 right);
 extern int audit_uid_comparator(kuid_t left, u32 op, kuid_t right);
 extern int audit_gid_comparator(kgid_t left, u32 op, kgid_t right);
 extern int parent_len(const char *path);
-extern int audit_compare_dname_path(const char *dname, const char *path);
+extern int audit_compare_dname_path(const char *dname, const char *path, int plen);
 extern struct sk_buff *     audit_make_reply(int pid, int seq, int type,
                                              int done, int multi,
                                              const void *payload, int size);
diff --git a/kernel/audit_watch.c b/kernel/audit_watch.c
index deb97c139e0c..9a9ae6e3d290 100644
--- a/kernel/audit_watch.c
+++ b/kernel/audit_watch.c
@@ -265,7 +265,8 @@ static void audit_update_watch(struct audit_parent *parent,
         /* Run all of the watches on this parent looking for the one that
          * matches the given dname */
         list_for_each_entry_safe(owatch, nextw, &parent->watches, wlist) {
-                if (audit_compare_dname_path(dname, owatch->path))
+                if (audit_compare_dname_path(dname, owatch->path,
+                                             AUDIT_NAME_FULL))
                         continue;
 
                 /* If the update involves invalidating rules, do the inode-based
diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
index d705eb17661b..7f19f23d38a3 100644
--- a/kernel/auditfilter.c
+++ b/kernel/auditfilter.c
@@ -1328,11 +1328,17 @@ int parent_len(const char *path)
         return p - path;
 }
 
-/* Compare given dentry name with last component in given path,
- * return of 0 indicates a match. */
-int audit_compare_dname_path(const char *dname, const char *path)
+/**
+ * audit_compare_dname_path - compare given dentry name with last component in
+ *                            given path. Return of 0 indicates a match.
+ * @dname:      dentry name that we're comparing
+ * @path:       full pathname that we're comparing
+ * @parentlen:  length of the parent if known. Passing in AUDIT_NAME_FULL
+ *              here indicates that we must compute this value.
+ */
+int audit_compare_dname_path(const char *dname, const char *path, int parentlen)
 {
-        int dlen, pathlen, parentlen;
+        int dlen, pathlen;
         const char *p;
 
         dlen = strlen(dname);
@@ -1340,7 +1346,7 @@ int audit_compare_dname_path(const char *dname, const char *path)
         if (pathlen < dlen)
                 return 1;
 
-        parentlen = parent_len(path);
+        parentlen = parentlen == AUDIT_NAME_FULL ? parent_len(path) : parentlen;
         if (pathlen - parentlen != dlen)
                 return 1;
 
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 09c7b6b4f8e6..0160a68b4d7f 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -81,9 +81,6 @@
  * a name dynamically and also add those to the list anchored by names_list. */
 #define AUDIT_NAMES     5
 
-/* Indicates that audit should log the full pathname. */
-#define AUDIT_NAME_FULL -1
-
 /* no execve audit message should be longer than this (userspace limits) */
 #define MAX_EXECVE_AUDIT_LEN 7500
 
@@ -2222,7 +2219,7 @@ void __audit_inode_child(const struct inode *parent,
                         continue;
 
                 if (n->ino == parent->i_ino &&
-                    !audit_compare_dname_path(dname, n->name)) {
+                    !audit_compare_dname_path(dname, n->name, n->name_len)) {
                         found_parent = n->name;
                         goto add_names;
                 }
@@ -2235,7 +2232,8 @@ void __audit_inode_child(const struct inode *parent,
 
                 /* strcmp() is the more likely scenario */
                 if (!strcmp(dname, n->name) ||
-                     !audit_compare_dname_path(dname, n->name)) {
+                    !audit_compare_dname_path(dname, n->name,
+                                                AUDIT_NAME_FULL)) {
                         if (inode)
                                 audit_copy_inode(n, dentry, inode);
                         else