Add stacking support to the seclvl module.
Note that seclvl is currently unable to prevent it's own unloading, as
it actually claims to do.
Changelog:
[Jul 26] Updated seclvl to use security_unlink_value to free
its data when seclvl is unloaded.
Signed-off-by: Serge Hallyn <[email protected]>
---
seclvl.c | 133 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-----
1 files changed, 123 insertions(+), 10 deletions(-)
Index: linux-2.6.13-rc3/security/seclvl.c
===================================================================
--- linux-2.6.13-rc3.orig/security/seclvl.c 2005-07-25 14:40:42.000000000 -0500
+++ linux-2.6.13-rc3/security/seclvl.c 2005-07-25 14:56:37.000000000 -0500
@@ -21,6 +21,7 @@
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/security.h>
+#include <linux/security-stack.h>
#include <linux/netlink.h>
#include <linux/fs.h>
#include <linux/namei.h>
@@ -35,6 +36,7 @@
#include <linux/sysfs.h>
#define SHA1_DIGEST_SIZE 20
+#define SECLVL_LSM_ID 0xF45
/**
* Module parameter that defines the initial secure level.
@@ -485,12 +487,46 @@ static int seclvl_settime(struct timespe
return 0;
}
+/*
+ * A structure which is stored with the inode when a process
+ * has a unmounted block device open for writing.
+ */
+struct seclvl_i_sec {
+ struct security_list lsm_list;
+ struct task_struct *task;
+ spinlock_t spinlock;
+ struct list_head chain;
+};
+
+static LIST_HEAD(seclvl_ichain);
+static DEFINE_SPINLOCK(seclvl_ichain_lock);
+
+static void seclvl_inode_free(struct inode *inode)
+{
+ struct seclvl_i_sec *isec;
+
+ isec = security_del_value_type(&inode->i_security, SECLVL_LSM_ID,
+ struct seclvl_i_sec);
+ if (isec) {
+ spin_lock(&seclvl_ichain_lock);
+ list_del(&isec->chain);
+ spin_unlock(&seclvl_ichain_lock);
+ if (isec->task == current)
+ isec->task = NULL;
+ kfree(isec);
+ }
+}
+
/* claim the blockdev to exclude mounters, release on file close */
-static int seclvl_bd_claim(struct inode *inode)
+static int seclvl_bd_claim(struct inode *inode, struct seclvl_i_sec *isec)
{
int holder;
struct block_device *bdev = NULL;
dev_t dev = inode->i_rdev;
+
+ if (isec->task && isec->task != current)
+ return -EPERM;
+
bdev = open_by_devnum(dev, FMODE_WRITE);
if (bdev) {
if (bd_claim(bdev, &holder)) {
@@ -498,7 +534,7 @@ static int seclvl_bd_claim(struct inode
return -EPERM;
}
/* claimed, mark it to release on close */
- inode->i_security = current;
+ isec->task = current;
}
return 0;
}
@@ -506,17 +542,60 @@ static int seclvl_bd_claim(struct inode
/* release the blockdev if you claimed it */
static void seclvl_bd_release(struct inode *inode)
{
- if (inode && S_ISBLK(inode->i_mode) && inode->i_security == current) {
- struct block_device *bdev = inode->i_bdev;
- if (bdev) {
- bd_release(bdev);
- blkdev_put(bdev);
- inode->i_security = NULL;
- }
+ struct seclvl_i_sec *isec;
+
+ if (inode && S_ISBLK(inode->i_mode)) {
+ isec = security_get_value_type(&inode->i_security,
+ SECLVL_LSM_ID, struct seclvl_i_sec);
+ if (!isec)
+ return;
+ spin_lock(&isec->spinlock);
+ if (isec->task == current) {
+ struct block_device *bdev = inode->i_bdev;
+ if (bdev) {
+ bd_release(bdev);
+ blkdev_put(bdev);
+ isec->task = NULL;
+ }
+ }
+ spin_unlock(&isec->spinlock);
}
}
/**
+ * Either returns the existing inode isec, or creates a new
+ * isec, places it on the inode->i_security list, and returns
+ * it.
+ * On error, return NULL.
+ */
+static struct seclvl_i_sec *
+seclvl_inode_get_or_alloc(struct inode *inode)
+{
+ struct seclvl_i_sec *isec;
+
+ isec = security_get_value_type(&inode->i_security,
+ SECLVL_LSM_ID, struct seclvl_i_sec);
+ if (isec)
+ return isec;
+ spin_lock(&seclvl_ichain_lock);
+ isec = security_get_value_type(&inode->i_security,
+ SECLVL_LSM_ID, struct seclvl_i_sec);
+ if (isec)
+ goto out;
+ isec = kmalloc(sizeof(struct seclvl_i_sec), GFP_KERNEL);
+ if (!isec)
+ goto out;
+ spin_lock_init(&isec->spinlock);
+ INIT_LIST_HEAD(&isec->chain);
+ list_add(&isec->chain, &seclvl_ichain);
+ security_add_value_type(&inode->i_security, SECLVL_LSM_ID, isec);
+
+out:
+ spin_unlock(&seclvl_ichain_lock);
+ return isec;
+}
+
+/**
* Security for writes to block devices is regulated by this seclvl
* function. Deny all writes to block devices in seclvl 2. In
* seclvl 1, we only deny writes to *mounted* block devices.
@@ -524,6 +603,8 @@ static void seclvl_bd_release(struct ino
static int
seclvl_inode_permission(struct inode *inode, int mask, struct nameidata *nd)
{
+ struct seclvl_i_sec *isec;
+
if (current->pid != 1 && S_ISBLK(inode->i_mode) && (mask & MAY_WRITE)) {
switch (seclvl) {
case 2:
@@ -531,13 +612,19 @@ seclvl_inode_permission(struct inode *in
"denied in secure level [%d]\n", seclvl);
return -EPERM;
case 1:
- if (seclvl_bd_claim(inode)) {
+ isec = seclvl_inode_get_or_alloc(inode);
+ if (!isec)
+ return -ENOMEM;
+ spin_lock(&isec->spinlock);
+ if (seclvl_bd_claim(inode, isec)) {
seclvl_printk(1, KERN_WARNING,
"Write to mounted block device "
"denied in secure level [%d]\n",
seclvl);
+ spin_unlock(&isec->spinlock);
return -EPERM;
}
+ spin_unlock(&isec->spinlock);
}
}
return 0;
@@ -596,6 +683,7 @@ static struct security_operations seclvl
.capable = seclvl_capable,
.inode_permission = seclvl_inode_permission,
.inode_setattr = seclvl_inode_setattr,
+ .inode_free_security = seclvl_inode_free,
.file_free_security = seclvl_file_free_security,
.settime = seclvl_settime,
.sb_umount = seclvl_umount,
@@ -720,6 +808,29 @@ static int __init seclvl_init(void)
return rc;
}
+/*
+ * free_ichain: Called when seclvl is unloaded to free all the memory
+ * it has attached to inodes.
+ * First we go through the list and remove the objects from the
+ * object chains (ie inode->i_security). Then we wait an rcu cycle.
+ * Then we can safely delete the object, as any any stacker m->hook()
+ * loop should have moved on to isec->lsm_list.next.
+ */
+static void free_ichain(void)
+{
+ struct seclvl_i_sec *isec, *n;
+
+ list_for_each_entry_safe(isec, n, &seclvl_ichain, chain) {
+ security_unlink_value(&isec->lsm_list.list);
+ }
+
+ synchronize_rcu();
+ list_for_each_entry_safe(isec, n, &seclvl_ichain, chain) {
+ list_del(&isec->chain);
+ kfree(isec);
+ }
+}
+
/**
* Remove the seclvl module.
*/
@@ -738,6 +849,8 @@ static void __exit seclvl_exit(void)
"seclvl: Failure unregistering with the "
"kernel\n");
}
+
+ free_ichain();
}
module_init(seclvl_init);
-
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