Smack: Improve access check performance

Each Smack label that the kernel has seen is added to a
list of labels. The list of access rules for a given subject
label hangs off of the label list entry for the label.
This patch changes the structures that contain subject
labels to point at the label list entry rather that the
label itself. Doing so removes a label list lookup in
smk_access() that was accounting for the largest single
chunk of Smack overhead.

Targeted for git://git.gitorious.org/smack-next/kernel.git

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>

1 files changed, 55 insertions, 53 deletions

diff --git a/security/smack/smack.h b/security/smack/smack.h
index bb28e099abfe..159f25bfcf45 100644
--- a/security/smack/smack.h
+++ b/security/smack/smack.h
@@ -29,6 +29,38 @@
 #define SMK_LONGLABEL   256
 
 /*
+ * This is the repository for labels seen so that it is
+ * not necessary to keep allocating tiny chuncks of memory
+ * and so that they can be shared.
+ *
+ * Labels are never modified in place. Anytime a label
+ * is imported (e.g. xattrset on a file) the list is checked
+ * for it and it is added if it doesn't exist. The address
+ * is passed out in either case. Entries are added, but
+ * never deleted.
+ *
+ * Since labels are hanging around anyway it doesn't
+ * hurt to maintain a secid for those awkward situations
+ * where kernel components that ought to use LSM independent
+ * interfaces don't. The secid should go away when all of
+ * these components have been repaired.
+ *
+ * The cipso value associated with the label gets stored here, too.
+ *
+ * Keep the access rules for this subject label here so that
+ * the entire set of rules does not need to be examined every
+ * time.
+ */
+struct smack_known {
+        struct list_head                list;
+        char                            *smk_known;
+        u32                             smk_secid;
+        struct netlbl_lsm_secattr       smk_netlabel;   /* on wire labels */
+        struct list_head                smk_rules;      /* access rules */
+        struct mutex                    smk_rules_lock; /* lock for rules */
+};
+
+/*
  * Maximum number of bytes for the levels in a CIPSO IP option.
  * Why 23? CIPSO is constrained to 30, so a 32 byte buffer is
  * bigger than can be used, and 24 is the next lower multiple
@@ -46,25 +78,25 @@ struct superblock_smack {
 };
 
 struct socket_smack {
-        char            *smk_out;       /* outbound label */
-        char            *smk_in;        /* inbound label */
-        char            *smk_packet;    /* TCP peer label */
+        struct smack_known      *smk_out;       /* outbound label */
+        char                    *smk_in;        /* inbound label */
+        char                    *smk_packet;    /* TCP peer label */
 };
 
 /*
  * Inode smack data
  */
 struct inode_smack {
-        char            *smk_inode;     /* label of the fso */
-        char            *smk_task;      /* label of the task */
-        char            *smk_mmap;      /* label of the mmap domain */
-        struct mutex    smk_lock;       /* initialization lock */
-        int             smk_flags;      /* smack inode flags */
+        char                    *smk_inode;     /* label of the fso */
+        struct smack_known      *smk_task;      /* label of the task */
+        struct smack_known      *smk_mmap;      /* label of the mmap domain */
+        struct mutex            smk_lock;       /* initialization lock */
+        int                     smk_flags;      /* smack inode flags */
 };
 
 struct task_smack {
-        char                    *smk_task;      /* label for access control */
-        char                    *smk_forked;    /* label when forked */
+        struct smack_known      *smk_task;      /* label for access control */
+        struct smack_known      *smk_forked;    /* label when forked */
         struct list_head        smk_rules;      /* per task access rules */
         struct mutex            smk_rules_lock; /* lock for the rules */
 };
@@ -78,7 +110,7 @@ struct task_smack {
  */
 struct smack_rule {
         struct list_head        list;
-        char                    *smk_subject;
+        struct smack_known      *smk_subject;
         char                    *smk_object;
         int                     smk_access;
 };
@@ -101,39 +133,7 @@ struct smk_port_label {
         struct sock             *smk_sock;      /* socket initialized on */
         unsigned short          smk_port;       /* the port number */
         char                    *smk_in;        /* incoming label */
-        char                    *smk_out;       /* outgoing label */
-};
-
-/*
- * This is the repository for labels seen so that it is
- * not necessary to keep allocating tiny chuncks of memory
- * and so that they can be shared.
- *
- * Labels are never modified in place. Anytime a label
- * is imported (e.g. xattrset on a file) the list is checked
- * for it and it is added if it doesn't exist. The address
- * is passed out in either case. Entries are added, but
- * never deleted.
- *
- * Since labels are hanging around anyway it doesn't
- * hurt to maintain a secid for those awkward situations
- * where kernel components that ought to use LSM independent
- * interfaces don't. The secid should go away when all of
- * these components have been repaired.
- *
- * The cipso value associated with the label gets stored here, too.
- *
- * Keep the access rules for this subject label here so that
- * the entire set of rules does not need to be examined every
- * time.
- */
-struct smack_known {
-        struct list_head                list;
-        char                            *smk_known;
-        u32                             smk_secid;
-        struct netlbl_lsm_secattr       smk_netlabel;   /* on wire labels */
-        struct list_head                smk_rules;      /* access rules */
-        struct mutex                    smk_rules_lock; /* lock for rules */
+        struct smack_known      *smk_out;       /* outgoing label */
 };
 
 /*
@@ -214,9 +214,9 @@ struct inode_smack *new_inode_smack(char *);
  * These functions are in smack_access.c
  */
 int smk_access_entry(char *, char *, struct list_head *);
-int smk_access(char *, char *, int, struct smk_audit_info *);
+int smk_access(struct smack_known *, char *, int, struct smk_audit_info *);
 int smk_curacc(char *, u32, struct smk_audit_info *);
-char *smack_from_secid(const u32);
+struct smack_known *smack_from_secid(const u32);
 char *smk_parse_smack(const char *string, int len);
 int smk_netlbl_mls(int, char *, struct netlbl_lsm_secattr *, int);
 char *smk_import(const char *, int);
@@ -229,7 +229,7 @@ u32 smack_to_secid(const char *);
  */
 extern int smack_cipso_direct;
 extern int smack_cipso_mapped;
-extern char *smack_net_ambient;
+extern struct smack_known *smack_net_ambient;
 extern char *smack_onlycap;
 extern const char *smack_cipso_option;
 
@@ -265,17 +265,17 @@ static inline char *smk_of_inode(const struct inode *isp)
 }
 
 /*
- * Present a pointer to the smack label in an task blob.
+ * Present a pointer to the smack label entry in an task blob.
  */
-static inline char *smk_of_task(const struct task_smack *tsp)
+static inline struct smack_known *smk_of_task(const struct task_smack *tsp)
 {
         return tsp->smk_task;
 }
 
 /*
- * Present a pointer to the forked smack label in an task blob.
+ * Present a pointer to the forked smack label entry in an task blob.
  */
-static inline char *smk_of_forked(const struct task_smack *tsp)
+static inline struct smack_known *smk_of_forked(const struct task_smack *tsp)
 {
         return tsp->smk_forked;
 }
@@ -283,7 +283,7 @@ static inline char *smk_of_forked(const struct task_smack *tsp)
 /*
  * Present a pointer to the smack label in the current task blob.
  */
-static inline char *smk_of_current(void)
+static inline struct smack_known *smk_of_current(void)
 {
         return smk_of_task(current_security());
 }
@@ -294,9 +294,11 @@ static inline char *smk_of_current(void)
  */
 static inline int smack_privileged(int cap)
 {
+        struct smack_known *skp = smk_of_current();
+
         if (!capable(cap))
                 return 0;
-        if (smack_onlycap == NULL || smack_onlycap == smk_of_current())
+        if (smack_onlycap == NULL || smack_onlycap == skp->smk_known)
                 return 1;
         return 0;
 }