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8083b1bf81
Add support for the missing ciphertext stealing part of the XTS-AES specification, which permits inputs of any size >= the block size. Cc: Pascal van Leeuwen <pvanleeuwen@verimatrix.com> Cc: Ondrej Mosnacek <omosnace@redhat.com> Tested-by: Milan Broz <gmazyland@gmail.com> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
480 lines
12 KiB
C
480 lines
12 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/* XTS: as defined in IEEE1619/D16
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* http://grouper.ieee.org/groups/1619/email/pdf00086.pdf
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*
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* Copyright (c) 2007 Rik Snel <rsnel@cube.dyndns.org>
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*
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* Based on ecb.c
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* Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
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*/
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#include <crypto/internal/skcipher.h>
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#include <crypto/scatterwalk.h>
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#include <linux/err.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/scatterlist.h>
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#include <linux/slab.h>
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#include <crypto/xts.h>
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#include <crypto/b128ops.h>
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#include <crypto/gf128mul.h>
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struct priv {
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struct crypto_skcipher *child;
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struct crypto_cipher *tweak;
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};
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struct xts_instance_ctx {
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struct crypto_skcipher_spawn spawn;
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char name[CRYPTO_MAX_ALG_NAME];
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};
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struct rctx {
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le128 t;
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struct scatterlist *tail;
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struct scatterlist sg[2];
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struct skcipher_request subreq;
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};
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static int setkey(struct crypto_skcipher *parent, const u8 *key,
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unsigned int keylen)
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{
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struct priv *ctx = crypto_skcipher_ctx(parent);
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struct crypto_skcipher *child;
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struct crypto_cipher *tweak;
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int err;
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err = xts_verify_key(parent, key, keylen);
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if (err)
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return err;
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keylen /= 2;
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/* we need two cipher instances: one to compute the initial 'tweak'
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* by encrypting the IV (usually the 'plain' iv) and the other
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* one to encrypt and decrypt the data */
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/* tweak cipher, uses Key2 i.e. the second half of *key */
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tweak = ctx->tweak;
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crypto_cipher_clear_flags(tweak, CRYPTO_TFM_REQ_MASK);
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crypto_cipher_set_flags(tweak, crypto_skcipher_get_flags(parent) &
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CRYPTO_TFM_REQ_MASK);
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err = crypto_cipher_setkey(tweak, key + keylen, keylen);
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crypto_skcipher_set_flags(parent, crypto_cipher_get_flags(tweak) &
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CRYPTO_TFM_RES_MASK);
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if (err)
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return err;
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/* data cipher, uses Key1 i.e. the first half of *key */
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child = ctx->child;
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crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
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crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
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CRYPTO_TFM_REQ_MASK);
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err = crypto_skcipher_setkey(child, key, keylen);
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crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
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CRYPTO_TFM_RES_MASK);
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return err;
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}
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/*
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* We compute the tweak masks twice (both before and after the ECB encryption or
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* decryption) to avoid having to allocate a temporary buffer and/or make
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* mutliple calls to the 'ecb(..)' instance, which usually would be slower than
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* just doing the gf128mul_x_ble() calls again.
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*/
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static int xor_tweak(struct skcipher_request *req, bool second_pass, bool enc)
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{
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struct rctx *rctx = skcipher_request_ctx(req);
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struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
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const bool cts = (req->cryptlen % XTS_BLOCK_SIZE);
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const int bs = XTS_BLOCK_SIZE;
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struct skcipher_walk w;
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le128 t = rctx->t;
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int err;
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if (second_pass) {
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req = &rctx->subreq;
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/* set to our TFM to enforce correct alignment: */
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skcipher_request_set_tfm(req, tfm);
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}
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err = skcipher_walk_virt(&w, req, false);
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while (w.nbytes) {
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unsigned int avail = w.nbytes;
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le128 *wsrc;
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le128 *wdst;
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wsrc = w.src.virt.addr;
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wdst = w.dst.virt.addr;
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do {
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if (unlikely(cts) &&
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w.total - w.nbytes + avail < 2 * XTS_BLOCK_SIZE) {
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if (!enc) {
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if (second_pass)
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rctx->t = t;
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gf128mul_x_ble(&t, &t);
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}
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le128_xor(wdst, &t, wsrc);
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if (enc && second_pass)
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gf128mul_x_ble(&rctx->t, &t);
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skcipher_walk_done(&w, avail - bs);
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return 0;
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}
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le128_xor(wdst++, &t, wsrc++);
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gf128mul_x_ble(&t, &t);
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} while ((avail -= bs) >= bs);
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err = skcipher_walk_done(&w, avail);
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}
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return err;
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}
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static int xor_tweak_pre(struct skcipher_request *req, bool enc)
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{
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return xor_tweak(req, false, enc);
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}
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static int xor_tweak_post(struct skcipher_request *req, bool enc)
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{
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return xor_tweak(req, true, enc);
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}
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static void cts_done(struct crypto_async_request *areq, int err)
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{
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struct skcipher_request *req = areq->data;
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le128 b;
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if (!err) {
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struct rctx *rctx = skcipher_request_ctx(req);
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scatterwalk_map_and_copy(&b, rctx->tail, 0, XTS_BLOCK_SIZE, 0);
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le128_xor(&b, &rctx->t, &b);
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scatterwalk_map_and_copy(&b, rctx->tail, 0, XTS_BLOCK_SIZE, 1);
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}
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skcipher_request_complete(req, err);
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}
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static int cts_final(struct skcipher_request *req,
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int (*crypt)(struct skcipher_request *req))
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{
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struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
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int offset = req->cryptlen & ~(XTS_BLOCK_SIZE - 1);
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struct rctx *rctx = skcipher_request_ctx(req);
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struct skcipher_request *subreq = &rctx->subreq;
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int tail = req->cryptlen % XTS_BLOCK_SIZE;
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le128 b[2];
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int err;
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rctx->tail = scatterwalk_ffwd(rctx->sg, req->dst,
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offset - XTS_BLOCK_SIZE);
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scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 0);
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memcpy(b + 1, b, tail);
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scatterwalk_map_and_copy(b, req->src, offset, tail, 0);
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le128_xor(b, &rctx->t, b);
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scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE + tail, 1);
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skcipher_request_set_tfm(subreq, ctx->child);
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skcipher_request_set_callback(subreq, req->base.flags, cts_done, req);
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skcipher_request_set_crypt(subreq, rctx->tail, rctx->tail,
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XTS_BLOCK_SIZE, NULL);
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err = crypt(subreq);
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if (err)
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return err;
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scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 0);
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le128_xor(b, &rctx->t, b);
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scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 1);
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return 0;
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}
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static void encrypt_done(struct crypto_async_request *areq, int err)
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{
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struct skcipher_request *req = areq->data;
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if (!err) {
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struct rctx *rctx = skcipher_request_ctx(req);
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rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
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err = xor_tweak_post(req, true);
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if (!err && unlikely(req->cryptlen % XTS_BLOCK_SIZE)) {
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err = cts_final(req, crypto_skcipher_encrypt);
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if (err == -EINPROGRESS)
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return;
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}
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}
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skcipher_request_complete(req, err);
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}
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static void decrypt_done(struct crypto_async_request *areq, int err)
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{
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struct skcipher_request *req = areq->data;
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if (!err) {
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struct rctx *rctx = skcipher_request_ctx(req);
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rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
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err = xor_tweak_post(req, false);
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if (!err && unlikely(req->cryptlen % XTS_BLOCK_SIZE)) {
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err = cts_final(req, crypto_skcipher_decrypt);
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if (err == -EINPROGRESS)
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return;
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}
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}
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skcipher_request_complete(req, err);
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}
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static int init_crypt(struct skcipher_request *req, crypto_completion_t compl)
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{
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struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
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struct rctx *rctx = skcipher_request_ctx(req);
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struct skcipher_request *subreq = &rctx->subreq;
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if (req->cryptlen < XTS_BLOCK_SIZE)
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return -EINVAL;
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skcipher_request_set_tfm(subreq, ctx->child);
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skcipher_request_set_callback(subreq, req->base.flags, compl, req);
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skcipher_request_set_crypt(subreq, req->dst, req->dst,
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req->cryptlen & ~(XTS_BLOCK_SIZE - 1), NULL);
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/* calculate first value of T */
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crypto_cipher_encrypt_one(ctx->tweak, (u8 *)&rctx->t, req->iv);
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return 0;
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}
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static int encrypt(struct skcipher_request *req)
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{
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struct rctx *rctx = skcipher_request_ctx(req);
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struct skcipher_request *subreq = &rctx->subreq;
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int err;
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err = init_crypt(req, encrypt_done) ?:
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xor_tweak_pre(req, true) ?:
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crypto_skcipher_encrypt(subreq) ?:
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xor_tweak_post(req, true);
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if (err || likely((req->cryptlen % XTS_BLOCK_SIZE) == 0))
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return err;
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return cts_final(req, crypto_skcipher_encrypt);
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}
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static int decrypt(struct skcipher_request *req)
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{
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struct rctx *rctx = skcipher_request_ctx(req);
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struct skcipher_request *subreq = &rctx->subreq;
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int err;
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err = init_crypt(req, decrypt_done) ?:
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xor_tweak_pre(req, false) ?:
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crypto_skcipher_decrypt(subreq) ?:
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xor_tweak_post(req, false);
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if (err || likely((req->cryptlen % XTS_BLOCK_SIZE) == 0))
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return err;
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return cts_final(req, crypto_skcipher_decrypt);
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}
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static int init_tfm(struct crypto_skcipher *tfm)
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{
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struct skcipher_instance *inst = skcipher_alg_instance(tfm);
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struct xts_instance_ctx *ictx = skcipher_instance_ctx(inst);
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struct priv *ctx = crypto_skcipher_ctx(tfm);
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struct crypto_skcipher *child;
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struct crypto_cipher *tweak;
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child = crypto_spawn_skcipher(&ictx->spawn);
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if (IS_ERR(child))
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return PTR_ERR(child);
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ctx->child = child;
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tweak = crypto_alloc_cipher(ictx->name, 0, 0);
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if (IS_ERR(tweak)) {
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crypto_free_skcipher(ctx->child);
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return PTR_ERR(tweak);
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}
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ctx->tweak = tweak;
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crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(child) +
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sizeof(struct rctx));
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return 0;
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}
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static void exit_tfm(struct crypto_skcipher *tfm)
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{
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struct priv *ctx = crypto_skcipher_ctx(tfm);
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crypto_free_skcipher(ctx->child);
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crypto_free_cipher(ctx->tweak);
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}
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static void free(struct skcipher_instance *inst)
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{
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crypto_drop_skcipher(skcipher_instance_ctx(inst));
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kfree(inst);
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}
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static int create(struct crypto_template *tmpl, struct rtattr **tb)
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{
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struct skcipher_instance *inst;
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struct crypto_attr_type *algt;
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struct xts_instance_ctx *ctx;
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struct skcipher_alg *alg;
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const char *cipher_name;
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u32 mask;
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int err;
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algt = crypto_get_attr_type(tb);
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if (IS_ERR(algt))
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return PTR_ERR(algt);
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if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
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return -EINVAL;
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cipher_name = crypto_attr_alg_name(tb[1]);
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if (IS_ERR(cipher_name))
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return PTR_ERR(cipher_name);
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inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL);
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if (!inst)
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return -ENOMEM;
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ctx = skcipher_instance_ctx(inst);
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crypto_set_skcipher_spawn(&ctx->spawn, skcipher_crypto_instance(inst));
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mask = crypto_requires_off(algt->type, algt->mask,
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CRYPTO_ALG_NEED_FALLBACK |
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CRYPTO_ALG_ASYNC);
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err = crypto_grab_skcipher(&ctx->spawn, cipher_name, 0, mask);
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if (err == -ENOENT) {
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err = -ENAMETOOLONG;
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if (snprintf(ctx->name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
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cipher_name) >= CRYPTO_MAX_ALG_NAME)
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goto err_free_inst;
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err = crypto_grab_skcipher(&ctx->spawn, ctx->name, 0, mask);
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}
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if (err)
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goto err_free_inst;
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alg = crypto_skcipher_spawn_alg(&ctx->spawn);
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err = -EINVAL;
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if (alg->base.cra_blocksize != XTS_BLOCK_SIZE)
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goto err_drop_spawn;
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if (crypto_skcipher_alg_ivsize(alg))
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goto err_drop_spawn;
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err = crypto_inst_setname(skcipher_crypto_instance(inst), "xts",
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&alg->base);
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if (err)
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goto err_drop_spawn;
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err = -EINVAL;
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cipher_name = alg->base.cra_name;
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/* Alas we screwed up the naming so we have to mangle the
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* cipher name.
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*/
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if (!strncmp(cipher_name, "ecb(", 4)) {
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unsigned len;
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len = strlcpy(ctx->name, cipher_name + 4, sizeof(ctx->name));
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if (len < 2 || len >= sizeof(ctx->name))
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goto err_drop_spawn;
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if (ctx->name[len - 1] != ')')
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goto err_drop_spawn;
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ctx->name[len - 1] = 0;
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if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
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"xts(%s)", ctx->name) >= CRYPTO_MAX_ALG_NAME) {
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err = -ENAMETOOLONG;
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goto err_drop_spawn;
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}
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} else
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goto err_drop_spawn;
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inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
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inst->alg.base.cra_priority = alg->base.cra_priority;
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inst->alg.base.cra_blocksize = XTS_BLOCK_SIZE;
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inst->alg.base.cra_alignmask = alg->base.cra_alignmask |
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(__alignof__(u64) - 1);
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inst->alg.ivsize = XTS_BLOCK_SIZE;
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inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) * 2;
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inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) * 2;
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inst->alg.base.cra_ctxsize = sizeof(struct priv);
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inst->alg.init = init_tfm;
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inst->alg.exit = exit_tfm;
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inst->alg.setkey = setkey;
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inst->alg.encrypt = encrypt;
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inst->alg.decrypt = decrypt;
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inst->free = free;
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err = skcipher_register_instance(tmpl, inst);
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if (err)
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goto err_drop_spawn;
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out:
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return err;
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err_drop_spawn:
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crypto_drop_skcipher(&ctx->spawn);
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err_free_inst:
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kfree(inst);
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goto out;
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}
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static struct crypto_template crypto_tmpl = {
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.name = "xts",
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.create = create,
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.module = THIS_MODULE,
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};
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static int __init crypto_module_init(void)
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{
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return crypto_register_template(&crypto_tmpl);
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}
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static void __exit crypto_module_exit(void)
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{
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crypto_unregister_template(&crypto_tmpl);
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}
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subsys_initcall(crypto_module_init);
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module_exit(crypto_module_exit);
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("XTS block cipher mode");
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MODULE_ALIAS_CRYPTO("xts");
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