Question

我尝试用cryptoapi编写Linux内核模块。我找到了一些这样的例子：https://codedream.me/2014/04/cryptoapi-linux-kernel/

这个例子对我有用。然后我做了一些改变。当我尝试加载模块时，我的系统崩溃了。你能帮我解决这个问题吗？

/* Common headers */
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/err.h>
/* crypto headers */
#include <linux/crypto.h>
#include <linux/err.h>
#include <linux/scatterlist.h>

#define AES_BLOCK_SIZE (16)
#define AES_IV_SIZE    (16)
#define AES_KEY_SIZE   (64) /* because we are using XTS mode */

typedef enum {
    ENCRYPT,
    DECRYPT
} cipher_mode;

static int crypt_data(u8 *key, u32 key_len, u8 *iv, u32 iv_len, u8 *dst, 
                      u32 dst_len, u8 *src, u8 src_len, cipher_mode mode)
{
    struct crypto_blkcipher *blk;
    struct blkcipher_desc desc;
    struct scatterlist sg[2];

    /* CRYPTO_ALG_TYPE_BLKCIPHER_MASK, CRYPTO_ALG_TYPE_BLKCIPHER */
    blk = crypto_alloc_blkcipher("xts(aes)", 0, 0);
    if (IS_ERR(blk)) {
        printk(KERN_ALERT "Failed to initialize AES-XTS mode\n");
        return -1;
    } else {
        printk(KERN_ALERT "Initialized cipher: %s\n", crypto_blkcipher_name(blk));
        printk(KERN_ALERT "with IV size: %d\n", crypto_blkcipher_ivsize(blk));
        printk(KERN_ALERT "block size: %d\n", crypto_blkcipher_blocksize(blk));
    }

    if (crypto_blkcipher_setkey(blk, key, key_len)) {
        printk(KERN_ALERT "Failed to set key.\n");
        goto err;
    }

    crypto_blkcipher_set_iv(blk, iv, iv_len);

    sg_init_one(&sg[0],src,src_len);
    sg_init_one(&sg[1],dst,dst_len);

    /* do encryption */
    desc.tfm = blk;
    desc.flags = 0;

    if (mode == ENCRYPT) {
        if (crypto_blkcipher_encrypt(&desc, &sg[1], &sg[0], src_len))
            printk(KERN_ALERT "Failed to encrypt.\n");
    } else {
        if (crypto_blkcipher_decrypt(&desc, &sg[1], &sg[0], src_len))
            printk(KERN_ALERT "Failed to encrypt.\n");
    }

    crypto_free_blkcipher(blk);
    return 0;

err:
    crypto_free_blkcipher(blk);
    return -1;
}

static int aes_crypt_init(void)
{
    int len = 5000;
    u8 key[AES_KEY_SIZE]; 
    u8 iv[AES_IV_SIZE];
    u8 src[len];
    u8 enc[len];
    u8 dec[len];
    int err = 0;

    printk(KERN_ALERT "AES crypto module start initialyzing.\n");
    err = crypt_data(key, AES_KEY_SIZE, iv, AES_IV_SIZE, enc, len, src, len, ENCRYPT);
    return err;
}

static void aes_crypt_exit(void)
{
    printk(KERN_ALERT "AES crypto module exiting.\n");
}

module_init(aes_crypt_init);
module_exit(aes_crypt_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Dmitry Falko");
MODULE_DESCRIPTION("Testing module crypto api for AES-XTS mode");

变量len = 1000时，模块正常加载。但如果我在len = 5000上更改它，我在加载模块时会出现系统崩溃。

我的系统是：Linux ubuntu-virtual-machine 3.13.0-65-generic #105-Ubuntu SMP Mon Sep 21 18:50:58 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

Answer 1

你可能用完了堆栈空间。内核线程中的堆栈极其有限;在堆栈上分配15 KB（5000 x 3）的数据是行不通的。

使用kmalloc()和kfree()分配大缓冲区。

使用Linux CryptoApi模块导致系统崩溃

1 个答案: