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Message-ID: <20170508214324.GA124468@beast>
Date: Mon, 8 May 2017 14:43:24 -0700
From: Kees Cook <keescook@...omium.org>
To: David Howells <dhowells@...hat.com>
Cc: James Morris <james.l.morris@...cle.com>,
"Serge E. Hallyn" <serge@...lyn.com>, keyrings@...r.kernel.org,
linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] key: Convert big_key payload.data to struct
There is a lot of needless casting happening in the big_key data payload.
This is harder to trivially verify by static analysis and specifically
the randstruct GCC plugin (which was unhappy about casting a struct
path across two entries of a void * array). This converts the payload to
the actually used structures (one pointer, one embedded struct, and one
size_t).
Signed-off-by: Kees Cook <keescook@...omium.org>
---
include/linux/key.h | 11 ++++++++++-
security/keys/big_key.c | 45 +++++++++++++++++----------------------------
2 files changed, 27 insertions(+), 29 deletions(-)
diff --git a/include/linux/key.h b/include/linux/key.h
index 78e25aabedaf..2390830e3b1a 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -24,6 +24,7 @@
#include <linux/atomic.h>
#include <linux/assoc_array.h>
#include <linux/refcount.h>
+#include <linux/path.h>
#ifdef __KERNEL__
#include <linux/uidgid.h>
@@ -92,7 +93,15 @@ struct keyring_index_key {
union key_payload {
void __rcu *rcu_data0;
- void *data[4];
+ union {
+ void *data[4];
+ /* Layout of big_key payload words. */
+ struct {
+ u8 *key_data;
+ struct path key_path;
+ size_t key_len;
+ };
+ };
};
/*****************************************************************************/
diff --git a/security/keys/big_key.c b/security/keys/big_key.c
index 835c1ab30d01..6a0feb964e4a 100644
--- a/security/keys/big_key.c
+++ b/security/keys/big_key.c
@@ -22,16 +22,6 @@
#include <crypto/skcipher.h>
/*
- * Layout of key payload words.
- */
-enum {
- big_key_data,
- big_key_path,
- big_key_path_2nd_part,
- big_key_len,
-};
-
-/*
* Crypto operation with big_key data
*/
enum big_key_op {
@@ -123,7 +113,7 @@ static int big_key_crypt(enum big_key_op op, u8 *data, size_t datalen, u8 *key)
*/
int big_key_preparse(struct key_preparsed_payload *prep)
{
- struct path *path = (struct path *)&prep->payload.data[big_key_path];
+ struct path *path = &prep->payload.key_path;
struct file *file;
u8 *enckey;
u8 *data = NULL;
@@ -138,7 +128,7 @@ int big_key_preparse(struct key_preparsed_payload *prep)
/* Set an arbitrary quota */
prep->quotalen = 16;
- prep->payload.data[big_key_len] = (void *)(unsigned long)datalen;
+ prep->payload.key_len = datalen;
if (datalen > BIG_KEY_FILE_THRESHOLD) {
/* Create a shmem file to store the data in. This will permit the data
@@ -190,7 +180,7 @@ int big_key_preparse(struct key_preparsed_payload *prep)
/* Pin the mount and dentry to the key so that we can open it again
* later
*/
- prep->payload.data[big_key_data] = enckey;
+ prep->payload.key_data = enckey;
*path = file->f_path;
path_get(path);
fput(file);
@@ -202,7 +192,7 @@ int big_key_preparse(struct key_preparsed_payload *prep)
if (!data)
return -ENOMEM;
- prep->payload.data[big_key_data] = data;
+ prep->payload.key_data = data;
memcpy(data, prep->data, prep->datalen);
}
return 0;
@@ -222,11 +212,11 @@ int big_key_preparse(struct key_preparsed_payload *prep)
void big_key_free_preparse(struct key_preparsed_payload *prep)
{
if (prep->datalen > BIG_KEY_FILE_THRESHOLD) {
- struct path *path = (struct path *)&prep->payload.data[big_key_path];
+ struct path *path = &prep->payload.key_path;
path_put(path);
}
- kfree(prep->payload.data[big_key_data]);
+ kfree(prep->payload.key_data);
}
/*
@@ -235,12 +225,12 @@ void big_key_free_preparse(struct key_preparsed_payload *prep)
*/
void big_key_revoke(struct key *key)
{
- struct path *path = (struct path *)&key->payload.data[big_key_path];
+ struct path *path = &key->payload.key_path;
/* clear the quota */
key_payload_reserve(key, 0);
if (key_is_instantiated(key) &&
- (size_t)key->payload.data[big_key_len] > BIG_KEY_FILE_THRESHOLD)
+ key->payload.key_len > BIG_KEY_FILE_THRESHOLD)
vfs_truncate(path, 0);
}
@@ -249,17 +239,17 @@ void big_key_revoke(struct key *key)
*/
void big_key_destroy(struct key *key)
{
- size_t datalen = (size_t)key->payload.data[big_key_len];
+ size_t datalen = key->payload.key_len;
if (datalen > BIG_KEY_FILE_THRESHOLD) {
- struct path *path = (struct path *)&key->payload.data[big_key_path];
+ struct path *path = &key->payload.key_path;
path_put(path);
path->mnt = NULL;
path->dentry = NULL;
}
- kfree(key->payload.data[big_key_data]);
- key->payload.data[big_key_data] = NULL;
+ kfree(key->payload.key_data);
+ key->payload.key_data = NULL;
}
/*
@@ -267,7 +257,7 @@ void big_key_destroy(struct key *key)
*/
void big_key_describe(const struct key *key, struct seq_file *m)
{
- size_t datalen = (size_t)key->payload.data[big_key_len];
+ size_t datalen = key->payload.key_len;
seq_puts(m, key->description);
@@ -283,17 +273,17 @@ void big_key_describe(const struct key *key, struct seq_file *m)
*/
long big_key_read(const struct key *key, char __user *buffer, size_t buflen)
{
- size_t datalen = (size_t)key->payload.data[big_key_len];
+ size_t datalen = key->payload.key_len;
long ret;
if (!buffer || buflen < datalen)
return datalen;
if (datalen > BIG_KEY_FILE_THRESHOLD) {
- struct path *path = (struct path *)&key->payload.data[big_key_path];
+ struct path *path = &key->payload.key_path;
struct file *file;
u8 *data;
- u8 *enckey = (u8 *)key->payload.data[big_key_data];
+ u8 *enckey = key->payload.key_data;
size_t enclen = ALIGN(datalen, crypto_skcipher_blocksize(big_key_skcipher));
data = kmalloc(enclen, GFP_KERNEL);
@@ -329,8 +319,7 @@ long big_key_read(const struct key *key, char __user *buffer, size_t buflen)
kfree(data);
} else {
ret = datalen;
- if (copy_to_user(buffer, key->payload.data[big_key_data],
- datalen) != 0)
+ if (copy_to_user(buffer, key->payload.key_data, datalen) != 0)
ret = -EFAULT;
}
--
2.7.4
--
Kees Cook
Pixel Security
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