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Subject[RFC][PATCH v1 5/9] ima: allocating iint improvements
Date
From: Dmitry Kasatkin <dmitry.kasatkin@intel.com>

With IMA-appraisal's removal of the iint mutex and taking the i_mutex
instead, allocating the iint becomes a lot simplier, as we don't need
to be concerned with two processes racing to allocate the iint. This
patch cleans up and improves performance for allocating the iint.

- removed redundant double i_mutex locking
- combined iint allocation with tree search
- replaced spinlock with rwlock/read_lock

Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@intel.com>
Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
---
include/linux/integrity.h | 7 ++--
security/integrity/iint.c | 61 ++++++++++++++++---------------------
security/integrity/ima/ima_main.c | 13 ++-----
3 files changed, 34 insertions(+), 47 deletions(-)
diff --git a/include/linux/integrity.h b/include/linux/integrity.h
index a0c4125..66c5fe9 100644
--- a/include/linux/integrity.h
+++ b/include/linux/integrity.h
@@ -22,13 +22,14 @@ enum integrity_status {

/* List of EVM protected security xattrs */
#ifdef CONFIG_INTEGRITY
-extern int integrity_inode_alloc(struct inode *inode);
+extern struct integrity_iint_cache *integrity_inode_get(struct inode *inode);
extern void integrity_inode_free(struct inode *inode);

#else
-static inline int integrity_inode_alloc(struct inode *inode)
+static inline struct integrity_iint_cache *
+ integrity_inode_get(struct inode *inode)
{
- return 0;
+ return NULL;
}

static inline void integrity_inode_free(struct inode *inode)
diff --git a/security/integrity/iint.c b/security/integrity/iint.c
index e600986..d82a5a1 100644
--- a/security/integrity/iint.c
+++ b/security/integrity/iint.c
@@ -22,7 +22,7 @@
#include "integrity.h"

static struct rb_root integrity_iint_tree = RB_ROOT;
-static DEFINE_SPINLOCK(integrity_iint_lock);
+static DEFINE_RWLOCK(integrity_iint_lock);
static struct kmem_cache *iint_cache __read_mostly;

int iint_initialized;
@@ -35,8 +35,6 @@ static struct integrity_iint_cache *__integrity_iint_find(struct inode *inode)
struct integrity_iint_cache *iint;
struct rb_node *n = integrity_iint_tree.rb_node;

- assert_spin_locked(&integrity_iint_lock);
-
while (n) {
iint = rb_entry(n, struct integrity_iint_cache, rb_node);

@@ -63,9 +61,9 @@ struct integrity_iint_cache *integrity_iint_find(struct inode *inode)
if (!IS_IMA(inode))
return NULL;

- spin_lock(&integrity_iint_lock);
+ read_lock(&integrity_iint_lock);
iint = __integrity_iint_find(inode);
- spin_unlock(&integrity_iint_lock);
+ read_unlock(&integrity_iint_lock);

return iint;
}
@@ -80,54 +78,47 @@ static void iint_free(struct integrity_iint_cache *iint)
}

/**
- * integrity_inode_alloc - allocate an iint associated with an inode
+ * integrity_inode_get - find or allocate an iint associated with an inode
* @inode: pointer to the inode
+ * @return: allocated iint
+ *
+ * Caller must lock i_mutex
*/
-int integrity_inode_alloc(struct inode *inode)
+struct integrity_iint_cache *integrity_inode_get(struct inode *inode)
{
struct rb_node **p;
- struct rb_node *new_node, *parent = NULL;
- struct integrity_iint_cache *new_iint, *test_iint;
- int rc;
+ struct rb_node *node, *parent = NULL;
+ struct integrity_iint_cache *iint, *test_iint;

- new_iint = kmem_cache_alloc(iint_cache, GFP_NOFS);
- if (!new_iint)
- return -ENOMEM;
+ iint = integrity_iint_find(inode);
+ if (iint)
+ return iint;

- new_iint->inode = inode;
- new_node = &new_iint->rb_node;
+ iint = kmem_cache_alloc(iint_cache, GFP_NOFS);
+ if (!iint)
+ return NULL;

- mutex_lock(&inode->i_mutex); /* i_flags */
- spin_lock(&integrity_iint_lock);
+ write_lock(&integrity_iint_lock);

p = &integrity_iint_tree.rb_node;
while (*p) {
parent = *p;
test_iint = rb_entry(parent, struct integrity_iint_cache,
rb_node);
- rc = -EEXIST;
if (inode < test_iint->inode)
p = &(*p)->rb_left;
- else if (inode > test_iint->inode)
- p = &(*p)->rb_right;
else
- goto out_err;
+ p = &(*p)->rb_right;
}

+ iint->inode = inode;
+ node = &iint->rb_node;
inode->i_flags |= S_IMA;
- rb_link_node(new_node, parent, p);
- rb_insert_color(new_node, &integrity_iint_tree);
+ rb_link_node(node, parent, p);
+ rb_insert_color(node, &integrity_iint_tree);

- spin_unlock(&integrity_iint_lock);
- mutex_unlock(&inode->i_mutex); /* i_flags */
-
- return 0;
-out_err:
- spin_unlock(&integrity_iint_lock);
- mutex_unlock(&inode->i_mutex); /* i_flags */
- iint_free(new_iint);
-
- return rc;
+ write_unlock(&integrity_iint_lock);
+ return iint;
}

/**
@@ -143,10 +134,10 @@ void integrity_inode_free(struct inode *inode)
if (!IS_IMA(inode))
return;

- spin_lock(&integrity_iint_lock);
+ write_lock(&integrity_iint_lock);
iint = __integrity_iint_find(inode);
rb_erase(&iint->rb_node, &integrity_iint_tree);
- spin_unlock(&integrity_iint_lock);
+ write_unlock(&integrity_iint_lock);

iint_free(iint);
}
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index f5d7f28..72e66fd 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -145,19 +145,14 @@ static int process_measurement(struct file *file, const unsigned char *filename,
if (!action)
return 0;

-retry:
- iint = integrity_iint_find(inode);
- if (!iint) {
- rc = integrity_inode_alloc(inode);
- if (!rc || rc == -EEXIST)
- goto retry;
- return rc;
- }
-
must_appraise = action & IMA_APPRAISE;

mutex_lock(&inode->i_mutex);

+ iint = integrity_inode_get(inode);
+ if (!iint)
+ goto out;
+
/* Determine if already appraised/measured based on bitmask
* (IMA_MEASURE, IMA_MEASURED, IMA_APPRAISE, IMA_APPRAISED) */
iint->flags |= action;
--
1.7.6.5


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