[RFC,09/10] LSM: Infrastructure managed file security blob

Commit Message

Casey Schaufler July 11, 2016, 7:31 p.m. UTC

Subject: [PATCH RFC 09/10] LSM: Infrastructure managed file security blob

Move management of the file security blob from the security
modules to the LSM infrastructure. Module hooks that are no longer
required are removed.

Smack was stuffing a pointer that it manages into file->f_security.
Now a blob big enough for the pointer is allocated by the infrastruture
and the pointer is saved there. It might make sense to revise the way
this module manages its file data.

Signed-off-by: Casey Schaufler <[e-mail]>
---
 include/linux/lsm_hooks.h  |  1 +
 security/apparmor/lsm.c    | 20 +-------------------
 security/security.c        | 34 ++++++++++++++++++++++++++++++++++
 security/selinux/hooks.c   | 25 ++-----------------------
 security/smack/smack.h     |  2 +-
 security/smack/smack_lsm.c | 26 +++++++++-----------------
 6 files changed, 48 insertions(+), 60 deletions(-)


--
To unsubscribe from this list: send the line "unsubscribe linux-security-module" in
the body of a message to [e-mail]
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Patch

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 6086045..51f40b3 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1849,6 +1849,7 @@  struct security_hook_list {
  */
 struct lsm_blob_sizes {
 	int	lbs_cred;
+	int	lbs_file;
 };
 
 /*
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index 1bd99fa..6c21b08 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -352,23 +352,6 @@  static int apparmor_file_open(struct file *file, const struct cred *cred)
 	return error;
 }
 
-static int apparmor_file_alloc_security(struct file *file)
-{
-	/* freed by apparmor_file_free_security */
-	file->f_security = aa_alloc_file_context(GFP_KERNEL);
-	if (!file->f_security)
-		return -ENOMEM;
-	return 0;
-
-}
-
-static void apparmor_file_free_security(struct file *file)
-{
-	struct aa_file_cxt *cxt = file_cxt(file);
-
-	aa_free_file_context(cxt);
-}
-
 static int common_file_perm(int op, struct file *file, u32 mask)
 {
 	struct aa_file_cxt *fcxt = file_cxt(file);
@@ -590,6 +573,7 @@  static int apparmor_task_setrlimit(struct task_struct *task,
 
 struct lsm_blob_sizes apparmor_blob_sizes = {
 	.lbs_cred = sizeof(struct aa_task_cxt),
+	.lbs_file = sizeof(struct aa_file_cxt),
 };
 
 static struct security_hook_list apparmor_hooks[] = {
@@ -612,8 +596,6 @@  static struct security_hook_list apparmor_hooks[] = {
 
 	LSM_HOOK_INIT(file_open, apparmor_file_open),
 	LSM_HOOK_INIT(file_permission, apparmor_file_permission),
-	LSM_HOOK_INIT(file_alloc_security, apparmor_file_alloc_security),
-	LSM_HOOK_INIT(file_free_security, apparmor_file_free_security),
 	LSM_HOOK_INIT(mmap_file, apparmor_mmap_file),
 	LSM_HOOK_INIT(file_mprotect, apparmor_file_mprotect),
 	LSM_HOOK_INIT(file_lock, apparmor_file_lock),
diff --git a/security/security.c b/security/security.c
index 69200ab..88a9b48 100644
--- a/security/security.c
+++ b/security/security.c
@@ -80,6 +80,7 @@  int __init security_init(void)
 
 #ifdef CONFIG_SECURITY_STACKING_DEBUG
 	pr_info("LSM: cred blob size       = %d\n", blob_sizes.lbs_cred);
+	pr_info("LSM: file blob size       = %d\n", blob_sizes.lbs_file);
 #endif
 
 	return 0;
@@ -199,6 +200,32 @@  static void __init lsm_set_size(int *need, int *lbs)
 void __init security_add_blobs(struct lsm_blob_sizes *needed)
 {
 	lsm_set_size(&needed->lbs_cred, &blob_sizes.lbs_cred);
+	lsm_set_size(&needed->lbs_file, &blob_sizes.lbs_file);
+}
+
+/**
+ * lsm_file_alloc - allocate a composite file blob
+ * @file: the file that needs a blob
+ *
+ * Allocate the file blob for all the modules
+ *
+ * Returns 0, or -ENOMEM if memory can't be allocated.
+ */
+int lsm_file_alloc(struct file *file)
+{
+#ifdef CONFIG_SECURITY_STACKING_DEBUG
+	if (file->f_security) {
+		pr_info("%s: Inbound file blob is not NULL.\n", __func__);
+		return 0;
+	}
+#endif
+	if (blob_sizes.lbs_file == 0)
+		return 0;
+
+	file->f_security = kzalloc(blob_sizes.lbs_file, GFP_KERNEL);
+	if (file->f_security == NULL)
+		return -ENOMEM;
+	return 0;
 }
 
 /*
@@ -865,12 +892,19 @@  int security_file_permission(struct file *file, int mask)
 
 int security_file_alloc(struct file *file)
 {
+	int rc = lsm_file_alloc(file);
+
+	if (rc)
+		return rc;
 	return call_int_hook(file_alloc_security, 0, file);
 }
 
 void security_file_free(struct file *file)
 {
 	call_void_hook(file_free_security, file);
+
+	kfree(file->f_security);
+	file->f_security = NULL;
 }
 
 int security_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 95a2de9..9d769f3 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -126,7 +126,6 @@  int selinux_enabled = 1;
 #endif
 
 static struct kmem_cache *sel_inode_cache;
-static struct kmem_cache *file_security_cache;
 
 /**
  * selinux_secmark_enabled - Check to see if SECMARK is currently enabled
@@ -355,27 +354,15 @@  static void inode_free_security(struct inode *inode)
 
 static int file_alloc_security(struct file *file)
 {
-	struct file_security_struct *fsec;
+	struct file_security_struct *fsec = selinux_file(file);
 	u32 sid = current_sid();
 
-	fsec = kmem_cache_zalloc(file_security_cache, GFP_KERNEL);
-	if (!fsec)
-		return -ENOMEM;
-
 	fsec->sid = sid;
 	fsec->fown_sid = sid;
-	file->f_security = fsec;
 
 	return 0;
 }
 
-static void file_free_security(struct file *file)
-{
-	struct file_security_struct *fsec = selinux_file(file);
-	file->f_security = NULL;
-	kmem_cache_free(file_security_cache, fsec);
-}
-
 static int superblock_alloc_security(struct super_block *sb)
 {
 	struct superblock_security_struct *sbsec;
@@ -3307,11 +3294,6 @@  static int selinux_file_alloc_security(struct file *file)
 	return file_alloc_security(file);
 }
 
-static void selinux_file_free_security(struct file *file)
-{
-	file_free_security(file);
-}
-
 /*
  * Check whether a task has the ioctl permission and cmd
  * operation to an inode.
@@ -5972,6 +5954,7 @@  static int selinux_key_getsecurity(struct key *key, char **_buffer)
 
 struct lsm_blob_sizes selinux_blob_sizes = {
 	.lbs_cred = sizeof(struct task_security_struct),
+	.lbs_file = sizeof(struct file_security_struct),
 };
 
 static struct security_hook_list selinux_hooks[] = {
@@ -6040,7 +6023,6 @@  static struct security_hook_list selinux_hooks[] = {
 
 	LSM_HOOK_INIT(file_permission, selinux_file_permission),
 	LSM_HOOK_INIT(file_alloc_security, selinux_file_alloc_security),
-	LSM_HOOK_INIT(file_free_security, selinux_file_free_security),
 	LSM_HOOK_INIT(file_ioctl, selinux_file_ioctl),
 	LSM_HOOK_INIT(mmap_file, selinux_mmap_file),
 	LSM_HOOK_INIT(mmap_addr, selinux_mmap_addr),
@@ -6215,9 +6197,6 @@  static __init int selinux_init(void)
 	sel_inode_cache = kmem_cache_create("selinux_inode_security",
 					    sizeof(struct inode_security_struct),
 					    0, SLAB_PANIC, NULL);
-	file_security_cache = kmem_cache_create("selinux_file_security",
-					    sizeof(struct file_security_struct),
-					    0, SLAB_PANIC, NULL);
 	avc_init();
 
 	security_add_hooks(selinux_hooks, ARRAY_SIZE(selinux_hooks), "selinux");
diff --git a/security/smack/smack.h b/security/smack/smack.h
index d929f3d..0027ccd 100644
--- a/security/smack/smack.h
+++ b/security/smack/smack.h
@@ -343,7 +343,7 @@  static inline struct task_smack *smack_cred(const struct cred *cred)
 	return cred->security;
 }
 
-static inline struct smack_known *smack_file(const struct file *file)
+static inline struct smack_known **smack_file(const struct file *file)
 {
 	return file->f_security;
 }
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index bce7c44..94aff94 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -1563,25 +1563,13 @@  static void smack_inode_getsecid(struct inode *inode, u32 *secid)
  */
 static int smack_file_alloc_security(struct file *file)
 {
-	struct smack_known *skp = smk_of_current();
+	struct smack_known **blob = smack_file(file);
 
-	file->f_security = skp;
+	*blob = smk_of_current();
 	return 0;
 }
 
 /**
- * smack_file_free_security - clear a file security blob
- * @file: the object
- *
- * The security blob for a file is a pointer to the master
- * label list, so no memory is freed.
- */
-static void smack_file_free_security(struct file *file)
-{
-	file->f_security = NULL;
-}
-
-/**
  * smack_file_ioctl - Smack check on ioctls
  * @file: the object
  * @cmd: what to do
@@ -1788,7 +1776,9 @@  static int smack_mmap_file(struct file *file,
  */
 static void smack_file_set_fowner(struct file *file)
 {
-	file->f_security = smk_of_current();
+	struct smack_known **blob = smack_file(file);
+
+	*blob = smk_of_current();
 }
 
 /**
@@ -1805,6 +1795,7 @@  static void smack_file_set_fowner(struct file *file)
 static int smack_file_send_sigiotask(struct task_struct *tsk,
 				     struct fown_struct *fown, int signum)
 {
+	struct smack_known **blob;
 	struct smack_known *skp;
 	struct smack_known *tkp = smk_of_task(smack_cred(tsk->cred));
 	struct file *file;
@@ -1817,7 +1808,8 @@  static int smack_file_send_sigiotask(struct task_struct *tsk,
 	file = container_of(fown, struct file, f_owner);
 
 	/* we don't log here as rc can be overriden */
-	skp = smack_file(file);
+	blob = smack_file(file);
+	skp = *blob;
 	rc = smk_access(skp, tkp, MAY_WRITE, NULL);
 	rc = smk_bu_note("sigiotask", skp, tkp, MAY_WRITE, rc);
 	if (rc != 0 && has_capability(tsk, CAP_MAC_OVERRIDE))
@@ -4554,6 +4546,7 @@  static int smack_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen)
 
 struct lsm_blob_sizes smack_blob_sizes = {
 	.lbs_cred = sizeof(struct task_smack),
+	.lbs_file = sizeof(struct smack_known *),
 };
 
 static struct security_hook_list smack_hooks[] = {
@@ -4593,7 +4586,6 @@  static struct security_hook_list smack_hooks[] = {
 	LSM_HOOK_INIT(inode_getsecid, smack_inode_getsecid),
 
 	LSM_HOOK_INIT(file_alloc_security, smack_file_alloc_security),
-	LSM_HOOK_INIT(file_free_security, smack_file_free_security),
 	LSM_HOOK_INIT(file_ioctl, smack_file_ioctl),
 	LSM_HOOK_INIT(file_lock, smack_file_lock),
 	LSM_HOOK_INIT(file_fcntl, smack_file_fcntl),