LSM: Infrastructure management of the file security
Move management of the file->f_security blob out of the
individual security modules and into the infrastructure.
The modules no longer allocate or free the data, instead
they tell the infrastructure how much space they require.
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
[kees: adjusted for ordered init series]
Signed-off-by: Kees Cook <keescook@chromium.org>
diff --git a/security/security.c b/security/security.c
index 09be8ce..f32d7d2 100644
--- a/security/security.c
+++ b/security/security.c
@@ -40,6 +40,8 @@
struct security_hook_heads security_hook_heads __lsm_ro_after_init;
static ATOMIC_NOTIFIER_HEAD(lsm_notifier_chain);
+static struct kmem_cache *lsm_file_cache;
+
char *lsm_names;
static struct lsm_blob_sizes blob_sizes __lsm_ro_after_init;
@@ -158,6 +160,7 @@
return;
lsm_set_blob_size(&needed->lbs_cred, &blob_sizes.lbs_cred);
+ lsm_set_blob_size(&needed->lbs_file, &blob_sizes.lbs_file);
}
/* Prepare LSM for initialization. */
@@ -279,6 +282,15 @@
prepare_lsm(*lsm);
init_debug("cred blob size = %d\n", blob_sizes.lbs_cred);
+ init_debug("file blob size = %d\n", blob_sizes.lbs_file);
+
+ /*
+ * Create any kmem_caches needed for blobs
+ */
+ if (blob_sizes.lbs_file)
+ lsm_file_cache = kmem_cache_create("lsm_file_cache",
+ blob_sizes.lbs_file, 0,
+ SLAB_PANIC, NULL);
for (lsm = ordered_lsms; *lsm; lsm++)
initialize_lsm(*lsm);
@@ -448,6 +460,27 @@
panic("%s: Early cred alloc failed.\n", __func__);
}
+/**
+ * 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.
+ */
+static int lsm_file_alloc(struct file *file)
+{
+ if (!lsm_file_cache) {
+ file->f_security = NULL;
+ return 0;
+ }
+
+ file->f_security = kmem_cache_zalloc(lsm_file_cache, GFP_KERNEL);
+ if (file->f_security == NULL)
+ return -ENOMEM;
+ return 0;
+}
+
/*
* Hook list operation macros.
*
@@ -1144,12 +1177,27 @@
int security_file_alloc(struct file *file)
{
- return call_int_hook(file_alloc_security, 0, file);
+ int rc = lsm_file_alloc(file);
+
+ if (rc)
+ return rc;
+ rc = call_int_hook(file_alloc_security, 0, file);
+ if (unlikely(rc))
+ security_file_free(file);
+ return rc;
}
void security_file_free(struct file *file)
{
+ void *blob;
+
call_void_hook(file_free_security, file);
+
+ blob = file->f_security;
+ if (blob) {
+ file->f_security = NULL;
+ kmem_cache_free(lsm_file_cache, blob);
+ }
}
int security_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
@@ -1267,7 +1315,7 @@
return rc;
rc = call_int_hook(cred_alloc_blank, 0, cred, gfp);
- if (rc)
+ if (unlikely(rc))
security_cred_free(cred);
return rc;
}
@@ -1288,7 +1336,7 @@
return rc;
rc = call_int_hook(cred_prepare, 0, new, old, gfp);
- if (rc)
+ if (unlikely(rc))
security_cred_free(new);
return rc;
}