IMA: move read counter into struct inode

IMA currently allocated an inode integrity structure for every inode in
core.  This stucture is about 120 bytes long.  Most files however
(especially on a system which doesn't make use of IMA) will never need
any of this space.  The problem is that if IMA is enabled we need to
know information about the number of readers and the number of writers
for every inode on the box.  At the moment we collect that information
in the per inode iint structure and waste the rest of the space.  This
patch moves those counters into the struct inode so we can eventually
stop allocating an IMA integrity structure except when absolutely
needed.

This patch does the minimum needed to move the location of the data.
Further cleanups, especially the location of counter updates, may still
be possible.

Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

6 files changed, 22 insertions, 34 deletions

diff --git a/fs/inode.c b/fs/inode.c
index 86464332e590..56d909d69bc8 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -24,6 +24,7 @@
 #include <linux/mount.h>
 #include <linux/async.h>
 #include <linux/posix_acl.h>
+#include <linux/ima.h>
 
 /*
  * This is needed for the following functions:
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 63d069bd80b7..01e3a0047fed 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -776,6 +776,10 @@ struct inode {
 
         unsigned int            i_flags;
 
+#ifdef CONFIG_IMA
+        /* protected by i_lock */
+        unsigned int            i_readcount; /* struct files open RO */
+#endif
         atomic_t                i_writecount;
 #ifdef CONFIG_SECURITY
         void                    *i_security;
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index b546b90f5fa8..27849e1656dc 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -70,6 +70,7 @@ int ima_init(void);
 void ima_cleanup(void);
 int ima_fs_init(void);
 void ima_fs_cleanup(void);
+int ima_inode_alloc(struct inode *inode);
 int ima_add_template_entry(struct ima_template_entry *entry, int violation,
                            const char *op, struct inode *inode);
 int ima_calc_hash(struct file *file, char *digest);
@@ -106,8 +107,6 @@ struct ima_iint_cache {
         unsigned char flags;
         u8 digest[IMA_DIGEST_SIZE];
         struct mutex mutex;     /* protects: version, flags, digest */
-        /* protected by inode->i_lock */
-        unsigned int readcount; /* measured files readcount */
         struct kref refcount;   /* ima_iint_cache reference count */
 };
 
diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
index 52015d098fdf..d3963de6003d 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -116,7 +116,7 @@ int ima_must_measure(struct ima_iint_cache *iint, struct inode *inode,
 {
         int must_measure;
 
-        if (iint->flags & IMA_MEASURED)
+        if (iint && iint->flags & IMA_MEASURED)
                 return 1;
 
         must_measure = ima_match_policy(inode, function, mask);
diff --git a/security/integrity/ima/ima_iint.c b/security/integrity/ima/ima_iint.c
index e68891f8d55a..0936a7197e47 100644
--- a/security/integrity/ima/ima_iint.c
+++ b/security/integrity/ima/ima_iint.c
@@ -124,11 +124,6 @@ void iint_free(struct kref *kref)
                                                    refcount);
         iint->version = 0;
         iint->flags = 0UL;
-        if (iint->readcount != 0) {
-                printk(KERN_INFO "%s: readcount: %u\n", __func__,
-                       iint->readcount);
-                iint->readcount = 0;
-        }
         kref_init(&iint->refcount);
         kmem_cache_free(iint_cache, iint);
 }
@@ -143,6 +138,11 @@ void ima_inode_free(struct inode *inode)
 {
         struct ima_iint_cache *iint;
 
+        if (inode->i_readcount)
+                printk(KERN_INFO "%s: readcount: %u\n", __func__, inode->i_readcount);
+
+        inode->i_readcount = 0;
+
         spin_lock(&ima_iint_lock);
         iint = __ima_iint_find(inode);
         if (iint)
@@ -160,7 +160,6 @@ static void init_once(void *foo)
         iint->version = 0;
         iint->flags = 0UL;
         mutex_init(&iint->mutex);
-        iint->readcount = 0;
         kref_init(&iint->refcount);
 }
 
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 24660bf3f82a..2a77b14fee27 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -86,17 +86,6 @@ out:
 }
 
 /*
- * Update the counts given an fmode_t
- */
-static void ima_inc_counts(struct ima_iint_cache *iint, fmode_t mode)
-{
-        assert_spin_locked(&iint->inode->i_lock);
-
-        if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
-                iint->readcount++;
-}
-
-/*
  * ima_counts_get - increment file counts
  *
  * Maintain read/write counters for all files, but only
@@ -112,27 +101,23 @@ void ima_counts_get(struct file *file)
         struct dentry *dentry = file->f_path.dentry;
         struct inode *inode = dentry->d_inode;
         fmode_t mode = file->f_mode;
-        struct ima_iint_cache *iint;
         int rc;
         bool send_tomtou = false, send_writers = false;
 
-        if (!iint_initialized || !S_ISREG(inode->i_mode))
+        if (!S_ISREG(inode->i_mode))
                 return;
-        iint = ima_iint_find_get(inode);
-        if (!iint)
-                return;
-        mutex_lock(&iint->mutex);
+
         spin_lock(&inode->i_lock);
 
         if (!ima_initialized)
                 goto out;
 
-        rc = ima_must_measure(iint, inode, MAY_READ, FILE_CHECK);
+        rc = ima_must_measure(NULL, inode, MAY_READ, FILE_CHECK);
         if (rc < 0)
                 goto out;
 
         if (mode & FMODE_WRITE) {
-                if (iint->readcount)
+                if (inode->i_readcount)
                         send_tomtou = true;
                 goto out;
         }
@@ -140,10 +125,10 @@ void ima_counts_get(struct file *file)
         if (atomic_read(&inode->i_writecount) > 0)
                 send_writers = true;
 out:
-        ima_inc_counts(iint, file->f_mode);
+        /* remember the vfs deals with i_writecount */
+        if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
+                inode->i_readcount++;
         spin_unlock(&inode->i_lock);
-        mutex_unlock(&iint->mutex);
-        kref_put(&iint->refcount, iint_free);
 
         if (send_tomtou)
                 ima_add_violation(inode, dentry->d_name.name, "invalid_pcr",
@@ -166,9 +151,9 @@ static void ima_dec_counts(struct ima_iint_cache *iint, struct inode *inode,
         assert_spin_locked(&inode->i_lock);
 
         if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ) {
-                if (unlikely(iint->readcount == 0))
+                if (unlikely(inode->i_readcount == 0))
                         dump = true;
-                iint->readcount--;
+                inode->i_readcount--;
         }
         if (mode & FMODE_WRITE) {
                 if (atomic_read(&inode->i_writecount) <= 0)
@@ -180,7 +165,7 @@ static void ima_dec_counts(struct ima_iint_cache *iint, struct inode *inode,
 
         if (dump && !ima_limit_imbalance(file)) {
                 printk(KERN_INFO "%s: open/free imbalance (r:%u)\n",
-                       __func__, iint->readcount);
+                       __func__, inode->i_readcount);
                 dump_stack();
         }
 }