On Wednesday, May 28, 2014 at 12:01:09 PM, Corentin LABBE wrote:
> Hello
>
> I have a problem when using a simple md5 tfm.
> When I use the data that ahash_request_ctx() give me, it will cause random
> crash when removing the module later. I do not understand it, because
> .cra_ctxsize seems to be rightly used.
>
> The very simplified POC code will follow, it register a fake md5
> implementation. If I remove the op->mode = 0, I can modprobe/rmmod for
> ever without problem. With it, rmmod will segfault in 2 or 3 tries, so it
> is this write that is the source of the problem.
>
> I have try to debug, but I cannot find where __ctx (the pointer returned by
> ahash_request_ctx) is allocated.
>
> Does I am right when saying: ahash_request_ctx() return the pointer to a
> structure of size equal to cra_ctxsize allocated for each request ?
crypto_tfm_ctx() returns per-transformation instance (tfm) private data
ahash_request_ctx() returns per-request private data
You need to configure the request context size via crypto_ahash_set_reqsize()
in
the implementations' .cra_init() callback .
[...]
static int my_cra_init(struct crypto_tfm *tfm)
{
crypto_ahash_set_reqsize(__crypto_ahash_cast(tfm),
sizeof(struct my_per_request_private_data));
return 0;
}
> static struct ahash_alg sunxi_md5_alg = {
> .init = fake_init,
> .update = fake_update,
> .final = fake_final,
> .finup = fake_finup,
> .digest = fake_digest,
> .halg = {
> .digestsize = MD5_DIGEST_SIZE,
> .base = {
> .cra_name = "md5",
> .cra_driver_name = "md5-sunxi-ss",
> .cra_priority = 300,
> .cra_alignmask = 3,
> .cra_flags = CRYPTO_ALG_TYPE_AHASH | CRYPTO_ALG_ASYNC,
> .cra_blocksize = MD5_HMAC_BLOCK_SIZE,
> .cra_ctxsize = sizeof(struct sunxi_req_ctx),
> .cra_module = THIS_MODULE,
> .cra_type = &crypto_ahash_type
.cra_init = my_cra_init,
> }
> }
> };
>
> static int sunxi_ss_md5_init(void)
> {
> int err = 0;
> err = crypto_register_ahash(&sunxi_md5_alg);
> if (err)
> pr_err("crypto_register_alg error for MD5\n");
> else
> pr_info("Registred MD5\n");
> return err;
> }
>
> static void __exit sunxi_ss_md5_exit(void)
> {
> crypto_unregister_ahash(&sunxi_md5_alg);
> }
>
> module_init(sunxi_ss_md5_init);
> module_exit(sunxi_ss_md5_exit);
module_platform_driver() here please, fix it up so this is a platform driver.
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