fs/ext4/crypto_fname.c - kernel/msm-4.9 - Gitiles

 /*
  * linux/fs/ext4/crypto_fname.c
  *
  * Copyright (C) 2015, Google, Inc.
  *
  * This contains functions for filename crypto management in ext4
  *
  * Written by Uday Savagaonkar, 2014.
  *
  * This has not yet undergone a rigorous security audit.
  *
  */

 #include <crypto/hash.h>
 #include <crypto/sha.h>
 #include <keys/encrypted-type.h>
 #include <keys/user-type.h>
 #include <linux/crypto.h>
 #include <linux/gfp.h>
 #include <linux/kernel.h>
 #include <linux/key.h>
 #include <linux/key.h>
 #include <linux/list.h>
 #include <linux/mempool.h>
 #include <linux/random.h>
 #include <linux/scatterlist.h>
 #include <linux/spinlock_types.h>

 #include "ext4.h"
 #include "ext4_crypto.h"
 #include "xattr.h"

 /**
  * ext4_dir_crypt_complete() -
  */
 static void ext4_dir_crypt_complete(struct crypto_async_request *req, int res)
 {
 	struct ext4_completion_result *ecr = req->data;

 	if (res == -EINPROGRESS)
 		return;
 	ecr->res = res;
 	complete(&ecr->completion);
 }

 bool ext4_valid_filenames_enc_mode(uint32_t mode)
 {
 	return (mode == EXT4_ENCRYPTION_MODE_AES_256_CTS);
 }

 /**
  * ext4_fname_encrypt() -
  *
  * This function encrypts the input filename, and returns the length of the
  * ciphertext. Errors are returned as negative numbers.  We trust the caller to
  * allocate sufficient memory to oname string.
  */
 static int ext4_fname_encrypt(struct ext4_fname_crypto_ctx *ctx,
 			      const struct qstr *iname,
 			      struct ext4_str *oname)
 {
 	u32 ciphertext_len;
 	struct ablkcipher_request *req = NULL;
 	DECLARE_EXT4_COMPLETION_RESULT(ecr);
 	struct crypto_ablkcipher *tfm = ctx->ctfm;
 	int res = 0;
 	char iv[EXT4_CRYPTO_BLOCK_SIZE];
 	struct scatterlist sg[1];
 	int padding = 4 << (ctx->flags & EXT4_POLICY_FLAGS_PAD_MASK);
 	char *workbuf;

 	if (iname->len <= 0 || iname->len > ctx->lim)
 		return -EIO;

 	ciphertext_len = (iname->len < EXT4_CRYPTO_BLOCK_SIZE) ?
 		EXT4_CRYPTO_BLOCK_SIZE : iname->len;
 	ciphertext_len = ext4_fname_crypto_round_up(ciphertext_len, padding);
 	ciphertext_len = (ciphertext_len > ctx->lim)
 			? ctx->lim : ciphertext_len;

 	/* Allocate request */
 	req = ablkcipher_request_alloc(tfm, GFP_NOFS);
 	if (!req) {
 		printk_ratelimited(
 		    KERN_ERR "%s: crypto_request_alloc() failed\n", __func__);
 		return -ENOMEM;
 	}
 	ablkcipher_request_set_callback(req,
 		CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
 		ext4_dir_crypt_complete, &ecr);

 	/* Map the workpage */
 	workbuf = kmap(ctx->workpage);

 	/* Copy the input */
 	memcpy(workbuf, iname->name, iname->len);
 	if (iname->len < ciphertext_len)
 		memset(workbuf + iname->len, 0, ciphertext_len - iname->len);

 	/* Initialize IV */
 	memset(iv, 0, EXT4_CRYPTO_BLOCK_SIZE);

 	/* Create encryption request */
 	sg_init_table(sg, 1);
 	sg_set_page(sg, ctx->workpage, PAGE_SIZE, 0);
 	ablkcipher_request_set_crypt(req, sg, sg, ciphertext_len, iv);
 	res = crypto_ablkcipher_encrypt(req);
 	if (res == -EINPROGRESS || res == -EBUSY) {
 		BUG_ON(req->base.data != &ecr);
 		wait_for_completion(&ecr.completion);
 		res = ecr.res;
 	}
 	if (res >= 0) {
 		/* Copy the result to output */
 		memcpy(oname->name, workbuf, ciphertext_len);
 		res = ciphertext_len;
 	}
 	kunmap(ctx->workpage);
 	ablkcipher_request_free(req);
 	if (res < 0) {
 		printk_ratelimited(
 		    KERN_ERR "%s: Error (error code %d)\n", __func__, res);
 	}
 	oname->len = ciphertext_len;
 	return res;
 }

 /*
  * ext4_fname_decrypt()
  *	This function decrypts the input filename, and returns
  *	the length of the plaintext.
  *	Errors are returned as negative numbers.
  *	We trust the caller to allocate sufficient memory to oname string.
  */
 static int ext4_fname_decrypt(struct ext4_fname_crypto_ctx *ctx,
 			      const struct ext4_str *iname,
 			      struct ext4_str *oname)
 {
 	struct ext4_str tmp_in[2], tmp_out[1];
 	struct ablkcipher_request *req = NULL;
 	DECLARE_EXT4_COMPLETION_RESULT(ecr);
 	struct scatterlist sg[1];
 	struct crypto_ablkcipher *tfm = ctx->ctfm;
 	int res = 0;
 	char iv[EXT4_CRYPTO_BLOCK_SIZE];
 	char *workbuf;

 	if (iname->len <= 0 || iname->len > ctx->lim)
 		return -EIO;

 	tmp_in[0].name = iname->name;
 	tmp_in[0].len = iname->len;
 	tmp_out[0].name = oname->name;

 	/* Allocate request */
 	req = ablkcipher_request_alloc(tfm, GFP_NOFS);
 	if (!req) {
 		printk_ratelimited(
 		    KERN_ERR "%s: crypto_request_alloc() failed\n",  __func__);
 		return -ENOMEM;
 	}
 	ablkcipher_request_set_callback(req,
 		CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
 		ext4_dir_crypt_complete, &ecr);

 	/* Map the workpage */
 	workbuf = kmap(ctx->workpage);

 	/* Copy the input */
 	memcpy(workbuf, iname->name, iname->len);

 	/* Initialize IV */
 	memset(iv, 0, EXT4_CRYPTO_BLOCK_SIZE);

 	/* Create encryption request */
 	sg_init_table(sg, 1);
 	sg_set_page(sg, ctx->workpage, PAGE_SIZE, 0);
 	ablkcipher_request_set_crypt(req, sg, sg, iname->len, iv);
 	res = crypto_ablkcipher_decrypt(req);
 	if (res == -EINPROGRESS || res == -EBUSY) {
 		BUG_ON(req->base.data != &ecr);
 		wait_for_completion(&ecr.completion);
 		res = ecr.res;
 	}
 	if (res >= 0) {
 		/* Copy the result to output */
 		memcpy(oname->name, workbuf, iname->len);
 		res = iname->len;
 	}
 	kunmap(ctx->workpage);
 	ablkcipher_request_free(req);
 	if (res < 0) {
 		printk_ratelimited(
 		    KERN_ERR "%s: Error in ext4_fname_encrypt (error code %d)\n",
 		    __func__, res);
 		return res;
 	}

 	oname->len = strnlen(oname->name, iname->len);
 	return oname->len;
 }

 static const char *lookup_table =
 	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";

 /**
  * ext4_fname_encode_digest() -
  *
  * Encodes the input digest using characters from the set [a-zA-Z0-9_+].
  * The encoded string is roughly 4/3 times the size of the input string.
  */
 static int digest_encode(const char *src, int len, char *dst)
 {
 	int i = 0, bits = 0, ac = 0;
 	char *cp = dst;

 	while (i < len) {
 		ac += (((unsigned char) src[i]) << bits);
 		bits += 8;
 		do {
 			*cp++ = lookup_table[ac & 0x3f];
 			ac >>= 6;
 			bits -= 6;
 		} while (bits >= 6);
 		i++;
 	}
 	if (bits)
 		*cp++ = lookup_table[ac & 0x3f];
 	return cp - dst;
 }

 static int digest_decode(const char *src, int len, char *dst)
 {
 	int i = 0, bits = 0, ac = 0;
 	const char *p;
 	char *cp = dst;

 	while (i < len) {
 		p = strchr(lookup_table, src[i]);
 		if (p == NULL || src[i] == 0)
 			return -2;
 		ac += (p - lookup_table) << bits;
 		bits += 6;
 		if (bits >= 8) {
 			*cp++ = ac & 0xff;
 			ac >>= 8;
 			bits -= 8;
 		}
 		i++;
 	}
 	if (ac)
 		return -1;
 	return cp - dst;
 }

 /**
  * ext4_free_fname_crypto_ctx() -
  *
  * Frees up a crypto context.
  */
 void ext4_free_fname_crypto_ctx(struct ext4_fname_crypto_ctx *ctx)
 {
 	if (ctx == NULL || IS_ERR(ctx))
 		return;

 	if (ctx->ctfm && !IS_ERR(ctx->ctfm))
 		crypto_free_ablkcipher(ctx->ctfm);
 	if (ctx->htfm && !IS_ERR(ctx->htfm))
 		crypto_free_hash(ctx->htfm);
 	if (ctx->workpage && !IS_ERR(ctx->workpage))
 		__free_page(ctx->workpage);
 	kfree(ctx);
 }

 /**
  * ext4_put_fname_crypto_ctx() -
  *
  * Return: The crypto context onto free list. If the free list is above a
  * threshold, completely frees up the context, and returns the memory.
  *
  * TODO: Currently we directly free the crypto context. Eventually we should
  * add code it to return to free list. Such an approach will increase
  * efficiency of directory lookup.
  */
 void ext4_put_fname_crypto_ctx(struct ext4_fname_crypto_ctx **ctx)
 {
 	if (*ctx == NULL || IS_ERR(*ctx))
 		return;
 	ext4_free_fname_crypto_ctx(*ctx);
 	*ctx = NULL;
 }

 /**
  * ext4_search_fname_crypto_ctx() -
  */
 static struct ext4_fname_crypto_ctx *ext4_search_fname_crypto_ctx(
 		const struct ext4_encryption_key *key)
 {
 	return NULL;
 }

 /**
  * ext4_alloc_fname_crypto_ctx() -
  */
 struct ext4_fname_crypto_ctx *ext4_alloc_fname_crypto_ctx(
 	const struct ext4_encryption_key *key)
 {
 	struct ext4_fname_crypto_ctx *ctx;

 	ctx = kmalloc(sizeof(struct ext4_fname_crypto_ctx), GFP_NOFS);
 	if (ctx == NULL)
 		return ERR_PTR(-ENOMEM);
 	if (key->mode == EXT4_ENCRYPTION_MODE_INVALID) {
 		/* This will automatically set key mode to invalid
 		 * As enum for ENCRYPTION_MODE_INVALID is zero */
 		memset(&ctx->key, 0, sizeof(ctx->key));
 	} else {
 		memcpy(&ctx->key, key, sizeof(struct ext4_encryption_key));
 	}
 	ctx->has_valid_key = (EXT4_ENCRYPTION_MODE_INVALID == key->mode)
 		? 0 : 1;
 	ctx->ctfm_key_is_ready = 0;
 	ctx->ctfm = NULL;
 	ctx->htfm = NULL;
 	ctx->workpage = NULL;
 	return ctx;
 }

 /**
  * ext4_get_fname_crypto_ctx() -
  *
  * Allocates a free crypto context and initializes it to hold
  * the crypto material for the inode.
  *
  * Return: NULL if not encrypted. Error value on error. Valid pointer otherwise.
  */
 struct ext4_fname_crypto_ctx *ext4_get_fname_crypto_ctx(
 	struct inode *inode, u32 max_ciphertext_len)
 {
 	struct ext4_fname_crypto_ctx *ctx;
 	struct ext4_inode_info *ei = EXT4_I(inode);
 	int res;

 	/* Check if the crypto policy is set on the inode */
 	res = ext4_encrypted_inode(inode);
 	if (res == 0)
 		return NULL;

 	if (!ext4_has_encryption_key(inode))
 		ext4_generate_encryption_key(inode);

 	/* Get a crypto context based on the key.
 	 * A new context is allocated if no context matches the requested key.
 	 */
 	ctx = ext4_search_fname_crypto_ctx(&(ei->i_encryption_key));
 	if (ctx == NULL)
 		ctx = ext4_alloc_fname_crypto_ctx(&(ei->i_encryption_key));
 	if (IS_ERR(ctx))
 		return ctx;

 	ctx->flags = ei->i_crypt_policy_flags;
 	if (ctx->has_valid_key) {
 		if (ctx->key.mode != EXT4_ENCRYPTION_MODE_AES_256_CTS) {
 			printk_once(KERN_WARNING
 				    "ext4: unsupported key mode %d\n",
 				    ctx->key.mode);
 			return ERR_PTR(-ENOKEY);
 		}

 		/* As a first cut, we will allocate new tfm in every call.
 		 * later, we will keep the tfm around, in case the key gets
 		 * re-used */
 		if (ctx->ctfm == NULL) {
 			ctx->ctfm = crypto_alloc_ablkcipher("cts(cbc(aes))",
 					0, 0);
 		}
 		if (IS_ERR(ctx->ctfm)) {
 			res = PTR_ERR(ctx->ctfm);
 			printk(
 			    KERN_DEBUG "%s: error (%d) allocating crypto tfm\n",
 			    __func__, res);
 			ctx->ctfm = NULL;
 			ext4_put_fname_crypto_ctx(&ctx);
 			return ERR_PTR(res);
 		}
 		if (ctx->ctfm == NULL) {
 			printk(
 			    KERN_DEBUG "%s: could not allocate crypto tfm\n",
 			    __func__);
 			ext4_put_fname_crypto_ctx(&ctx);
 			return ERR_PTR(-ENOMEM);
 		}
 		if (ctx->workpage == NULL)
 			ctx->workpage = alloc_page(GFP_NOFS);
 		if (IS_ERR(ctx->workpage)) {
 			res = PTR_ERR(ctx->workpage);
 			printk(
 			    KERN_DEBUG "%s: error (%d) allocating work page\n",
 			    __func__, res);
 			ctx->workpage = NULL;
 			ext4_put_fname_crypto_ctx(&ctx);
 			return ERR_PTR(res);
 		}
 		if (ctx->workpage == NULL) {
 			printk(
 			    KERN_DEBUG "%s: could not allocate work page\n",
 			    __func__);
 			ext4_put_fname_crypto_ctx(&ctx);
 			return ERR_PTR(-ENOMEM);
 		}
 		ctx->lim = max_ciphertext_len;
 		crypto_ablkcipher_clear_flags(ctx->ctfm, ~0);
 		crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctx->ctfm),
 			CRYPTO_TFM_REQ_WEAK_KEY);

 		/* If we are lucky, we will get a context that is already
 		 * set up with the right key. Else, we will have to
 		 * set the key */
 		if (!ctx->ctfm_key_is_ready) {
 			/* Since our crypto objectives for filename encryption
 			 * are pretty weak,
 			 * we directly use the inode master key */
 			res = crypto_ablkcipher_setkey(ctx->ctfm,
 					ctx->key.raw, ctx->key.size);
 			if (res) {
 				ext4_put_fname_crypto_ctx(&ctx);
 				return ERR_PTR(-EIO);
 			}
 			ctx->ctfm_key_is_ready = 1;
 		} else {
 			/* In the current implementation, key should never be
 			 * marked "ready" for a context that has just been
 			 * allocated. So we should never reach here */
 			 BUG();
 		}
 	}
 	if (ctx->htfm == NULL)
 		ctx->htfm = crypto_alloc_hash("sha256", 0, CRYPTO_ALG_ASYNC);
 	if (IS_ERR(ctx->htfm)) {
 		res = PTR_ERR(ctx->htfm);
 		printk(KERN_DEBUG "%s: error (%d) allocating hash tfm\n",
 			__func__, res);
 		ctx->htfm = NULL;
 		ext4_put_fname_crypto_ctx(&ctx);
 		return ERR_PTR(res);
 	}
 	if (ctx->htfm == NULL) {
 		printk(KERN_DEBUG "%s: could not allocate hash tfm\n",
 				__func__);
 		ext4_put_fname_crypto_ctx(&ctx);
 		return ERR_PTR(-ENOMEM);
 	}

 	return ctx;
 }

 /**
  * ext4_fname_crypto_round_up() -
  *
  * Return: The next multiple of block size
  */
 u32 ext4_fname_crypto_round_up(u32 size, u32 blksize)
 {
 	return ((size+blksize-1)/blksize)*blksize;
 }

 /**
  * ext4_fname_crypto_namelen_on_disk() -
  */
 int ext4_fname_crypto_namelen_on_disk(struct ext4_fname_crypto_ctx *ctx,
 				      u32 namelen)
 {
 	u32 ciphertext_len;
 	int padding = 4 << (ctx->flags & EXT4_POLICY_FLAGS_PAD_MASK);

 	if (ctx == NULL)
 		return -EIO;
 	if (!(ctx->has_valid_key))
 		return -EACCES;
 	ciphertext_len = (namelen < EXT4_CRYPTO_BLOCK_SIZE) ?
 		EXT4_CRYPTO_BLOCK_SIZE : namelen;
 	ciphertext_len = ext4_fname_crypto_round_up(ciphertext_len, padding);
 	ciphertext_len = (ciphertext_len > ctx->lim)
 			? ctx->lim : ciphertext_len;
 	return (int) ciphertext_len;
 }

 /**
  * ext4_fname_crypto_alloc_obuff() -
  *
  * Allocates an output buffer that is sufficient for the crypto operation
  * specified by the context and the direction.
  */
 int ext4_fname_crypto_alloc_buffer(struct ext4_fname_crypto_ctx *ctx,
 				   u32 ilen, struct ext4_str *crypto_str)
 {
 	unsigned int olen;
 	int padding = 4 << (ctx->flags & EXT4_POLICY_FLAGS_PAD_MASK);

 	if (!ctx)
 		return -EIO;
 	if (padding < EXT4_CRYPTO_BLOCK_SIZE)
 		padding = EXT4_CRYPTO_BLOCK_SIZE;
 	olen = ext4_fname_crypto_round_up(ilen, padding);
 	crypto_str->len = olen;
 	if (olen < EXT4_FNAME_CRYPTO_DIGEST_SIZE*2)
 		olen = EXT4_FNAME_CRYPTO_DIGEST_SIZE*2;
 	/* Allocated buffer can hold one more character to null-terminate the
 	 * string */
 	crypto_str->name = kmalloc(olen+1, GFP_NOFS);
 	if (!(crypto_str->name))
 		return -ENOMEM;
 	return 0;
 }

 /**
  * ext4_fname_crypto_free_buffer() -
  *
  * Frees the buffer allocated for crypto operation.
  */
 void ext4_fname_crypto_free_buffer(struct ext4_str *crypto_str)
 {
 	if (!crypto_str)
 		return;
 	kfree(crypto_str->name);
 	crypto_str->name = NULL;
 }

 /**
  * ext4_fname_disk_to_usr() - converts a filename from disk space to user space
  */
 int _ext4_fname_disk_to_usr(struct ext4_fname_crypto_ctx *ctx,
 			    struct dx_hash_info *hinfo,
 			    const struct ext4_str *iname,
 			    struct ext4_str *oname)
 {
 	char buf[24];
 	int ret;

 	if (ctx == NULL)
 		return -EIO;
 	if (iname->len < 3) {
 		/*Check for . and .. */
 		if (iname->name[0] == '.' && iname->name[iname->len-1] == '.') {
 			oname->name[0] = '.';
 			oname->name[iname->len-1] = '.';
 			oname->len = iname->len;
 			return oname->len;
 		}
 	}
 	if (ctx->has_valid_key)
 		return ext4_fname_decrypt(ctx, iname, oname);

 	if (iname->len <= EXT4_FNAME_CRYPTO_DIGEST_SIZE) {
 		ret = digest_encode(iname->name, iname->len, oname->name);
 		oname->len = ret;
 		return ret;
 	}
 	if (hinfo) {
 		memcpy(buf, &hinfo->hash, 4);
 		memcpy(buf+4, &hinfo->minor_hash, 4);
 	} else
 		memset(buf, 0, 8);
 	memcpy(buf + 8, iname->name + iname->len - 16, 16);
 	oname->name[0] = '_';
 	ret = digest_encode(buf, 24, oname->name+1);
 	oname->len = ret + 1;
 	return ret + 1;
 }

 int ext4_fname_disk_to_usr(struct ext4_fname_crypto_ctx *ctx,
 			   struct dx_hash_info *hinfo,
 			   const struct ext4_dir_entry_2 *de,
 			   struct ext4_str *oname)
 {
 	struct ext4_str iname = {.name = (unsigned char *) de->name,
 				 .len = de->name_len };

 	return _ext4_fname_disk_to_usr(ctx, hinfo, &iname, oname);
 }


 /**
  * ext4_fname_usr_to_disk() - converts a filename from user space to disk space
  */
 int ext4_fname_usr_to_disk(struct ext4_fname_crypto_ctx *ctx,
 			   const struct qstr *iname,
 			   struct ext4_str *oname)
 {
 	int res;

 	if (ctx == NULL)
 		return -EIO;
 	if (iname->len < 3) {
 		/*Check for . and .. */
 		if (iname->name[0] == '.' &&
 				iname->name[iname->len-1] == '.') {
 			oname->name[0] = '.';
 			oname->name[iname->len-1] = '.';
 			oname->len = iname->len;
 			return oname->len;
 		}
 	}
 	if (ctx->has_valid_key) {
 		res = ext4_fname_encrypt(ctx, iname, oname);
 		return res;
 	}
 	/* Without a proper key, a user is not allowed to modify the filenames
 	 * in a directory. Consequently, a user space name cannot be mapped to
 	 * a disk-space name */
 	return -EACCES;
 }

 /*
  * Calculate the htree hash from a filename from user space
  */
 int ext4_fname_usr_to_hash(struct ext4_fname_crypto_ctx *ctx,
 			    const struct qstr *iname,
 			    struct dx_hash_info *hinfo)
 {
 	struct ext4_str tmp;
 	int ret = 0;
 	char buf[EXT4_FNAME_CRYPTO_DIGEST_SIZE+1];

 	if (!ctx ||
 	    ((iname->name[0] == '.') &&
 	     ((iname->len == 1) ||
 	      ((iname->name[1] == '.') && (iname->len == 2))))) {
 		ext4fs_dirhash(iname->name, iname->len, hinfo);
 		return 0;
 	}

 	if (!ctx->has_valid_key && iname->name[0] == '_') {
 		if (iname->len != 33)
 			return -ENOENT;
 		ret = digest_decode(iname->name+1, iname->len, buf);
 		if (ret != 24)
 			return -ENOENT;
 		memcpy(&hinfo->hash, buf, 4);
 		memcpy(&hinfo->minor_hash, buf + 4, 4);
 		return 0;
 	}

 	if (!ctx->has_valid_key && iname->name[0] != '_') {
 		if (iname->len > 43)
 			return -ENOENT;
 		ret = digest_decode(iname->name, iname->len, buf);
 		ext4fs_dirhash(buf, ret, hinfo);
 		return 0;
 	}

 	/* First encrypt the plaintext name */
 	ret = ext4_fname_crypto_alloc_buffer(ctx, iname->len, &tmp);
 	if (ret < 0)
 		return ret;

 	ret = ext4_fname_encrypt(ctx, iname, &tmp);
 	if (ret >= 0) {
 		ext4fs_dirhash(tmp.name, tmp.len, hinfo);
 		ret = 0;
 	}

 	ext4_fname_crypto_free_buffer(&tmp);
 	return ret;
 }

 int ext4_fname_match(struct ext4_fname_crypto_ctx *ctx, struct ext4_str *cstr,
 		     int len, const char * const name,
 		     struct ext4_dir_entry_2 *de)
 {
 	int ret = -ENOENT;
 	int bigname = (*name == '_');

 	if (ctx->has_valid_key) {
 		if (cstr->name == NULL) {
 			struct qstr istr;

 			ret = ext4_fname_crypto_alloc_buffer(ctx, len, cstr);
 			if (ret < 0)
 				goto errout;
 			istr.name = name;
 			istr.len = len;
 			ret = ext4_fname_encrypt(ctx, &istr, cstr);
 			if (ret < 0)
 				goto errout;
 		}
 	} else {
 		if (cstr->name == NULL) {
 			cstr->name = kmalloc(32, GFP_KERNEL);
 			if (cstr->name == NULL)
 				return -ENOMEM;
 			if ((bigname && (len != 33)) ||
 			    (!bigname && (len > 43)))
 				goto errout;
 			ret = digest_decode(name+bigname, len-bigname,
 					    cstr->name);
 			if (ret < 0) {
 				ret = -ENOENT;
 				goto errout;
 			}
 			cstr->len = ret;
 		}
 		if (bigname) {
 			if (de->name_len < 16)
 				return 0;
 			ret = memcmp(de->name + de->name_len - 16,
 				     cstr->name + 8, 16);
 			return (ret == 0) ? 1 : 0;
 		}
 	}
 	if (de->name_len != cstr->len)
 		return 0;
 	ret = memcmp(de->name, cstr->name, cstr->len);
 	return (ret == 0) ? 1 : 0;
 errout:
 	kfree(cstr->name);
 	cstr->name = NULL;
 	return ret;
 }
	/*
	* linux/fs/ext4/crypto_fname.c
	*
	* Copyright (C) 2015, Google, Inc.
	*
	* This contains functions for filename crypto management in ext4
	*
	* Written by Uday Savagaonkar, 2014.
	*
	* This has not yet undergone a rigorous security audit.
	*
	*/

	#include <crypto/hash.h>
	#include <crypto/sha.h>
	#include <keys/encrypted-type.h>
	#include <keys/user-type.h>
	#include <linux/crypto.h>
	#include <linux/gfp.h>
	#include <linux/kernel.h>
	#include <linux/key.h>
	#include <linux/key.h>
	#include <linux/list.h>
	#include <linux/mempool.h>
	#include <linux/random.h>
	#include <linux/scatterlist.h>
	#include <linux/spinlock_types.h>

	#include "ext4.h"
	#include "ext4_crypto.h"
	#include "xattr.h"

	/**
	* ext4_dir_crypt_complete() -
	*/
	static void ext4_dir_crypt_complete(struct crypto_async_request *req, int res)
	{
	struct ext4_completion_result *ecr = req->data;

	if (res == -EINPROGRESS)
	return;
	ecr->res = res;
	complete(&ecr->completion);
	}

	bool ext4_valid_filenames_enc_mode(uint32_t mode)
	{
	return (mode == EXT4_ENCRYPTION_MODE_AES_256_CTS);
	}

	/**
	* ext4_fname_encrypt() -
	*
	* This function encrypts the input filename, and returns the length of the
	* ciphertext. Errors are returned as negative numbers. We trust the caller to
	* allocate sufficient memory to oname string.
	*/
	static int ext4_fname_encrypt(struct ext4_fname_crypto_ctx *ctx,
	const struct qstr *iname,
	struct ext4_str *oname)
	{
	u32 ciphertext_len;
	struct ablkcipher_request *req = NULL;
	DECLARE_EXT4_COMPLETION_RESULT(ecr);
	struct crypto_ablkcipher *tfm = ctx->ctfm;
	int res = 0;
	char iv[EXT4_CRYPTO_BLOCK_SIZE];
	struct scatterlist sg[1];
	int padding = 4 << (ctx->flags & EXT4_POLICY_FLAGS_PAD_MASK);
	char *workbuf;

	if (iname->len <= 0 \|\| iname->len > ctx->lim)
	return -EIO;

	ciphertext_len = (iname->len < EXT4_CRYPTO_BLOCK_SIZE) ?
	EXT4_CRYPTO_BLOCK_SIZE : iname->len;
	ciphertext_len = ext4_fname_crypto_round_up(ciphertext_len, padding);
	ciphertext_len = (ciphertext_len > ctx->lim)
	? ctx->lim : ciphertext_len;

	/* Allocate request */
	req = ablkcipher_request_alloc(tfm, GFP_NOFS);
	if (!req) {
	printk_ratelimited(
	KERN_ERR "%s: crypto_request_alloc() failed\n", __func__);
	return -ENOMEM;
	}
	ablkcipher_request_set_callback(req,
	CRYPTO_TFM_REQ_MAY_BACKLOG \| CRYPTO_TFM_REQ_MAY_SLEEP,
	ext4_dir_crypt_complete, &ecr);

	/* Map the workpage */
	workbuf = kmap(ctx->workpage);

	/* Copy the input */
	memcpy(workbuf, iname->name, iname->len);
	if (iname->len < ciphertext_len)
	memset(workbuf + iname->len, 0, ciphertext_len - iname->len);

	/* Initialize IV */
	memset(iv, 0, EXT4_CRYPTO_BLOCK_SIZE);

	/* Create encryption request */
	sg_init_table(sg, 1);
	sg_set_page(sg, ctx->workpage, PAGE_SIZE, 0);
	ablkcipher_request_set_crypt(req, sg, sg, ciphertext_len, iv);
	res = crypto_ablkcipher_encrypt(req);
	if (res == -EINPROGRESS \|\| res == -EBUSY) {
	BUG_ON(req->base.data != &ecr);
	wait_for_completion(&ecr.completion);
	res = ecr.res;
	}
	if (res >= 0) {
	/* Copy the result to output */
	memcpy(oname->name, workbuf, ciphertext_len);
	res = ciphertext_len;
	}
	kunmap(ctx->workpage);
	ablkcipher_request_free(req);
	if (res < 0) {
	printk_ratelimited(
	KERN_ERR "%s: Error (error code %d)\n", __func__, res);
	}
	oname->len = ciphertext_len;
	return res;
	}

	/*
	* ext4_fname_decrypt()
	* This function decrypts the input filename, and returns
	* the length of the plaintext.
	* Errors are returned as negative numbers.
	* We trust the caller to allocate sufficient memory to oname string.
	*/
	static int ext4_fname_decrypt(struct ext4_fname_crypto_ctx *ctx,
	const struct ext4_str *iname,
	struct ext4_str *oname)
	{
	struct ext4_str tmp_in[2], tmp_out[1];
	struct ablkcipher_request *req = NULL;
	DECLARE_EXT4_COMPLETION_RESULT(ecr);
	struct scatterlist sg[1];
	struct crypto_ablkcipher *tfm = ctx->ctfm;
	int res = 0;
	char iv[EXT4_CRYPTO_BLOCK_SIZE];
	char *workbuf;

	if (iname->len <= 0 \|\| iname->len > ctx->lim)
	return -EIO;

	tmp_in[0].name = iname->name;
	tmp_in[0].len = iname->len;
	tmp_out[0].name = oname->name;

	/* Allocate request */
	req = ablkcipher_request_alloc(tfm, GFP_NOFS);
	if (!req) {
	printk_ratelimited(
	KERN_ERR "%s: crypto_request_alloc() failed\n", __func__);
	return -ENOMEM;
	}
	ablkcipher_request_set_callback(req,
	CRYPTO_TFM_REQ_MAY_BACKLOG \| CRYPTO_TFM_REQ_MAY_SLEEP,
	ext4_dir_crypt_complete, &ecr);

	/* Map the workpage */
	workbuf = kmap(ctx->workpage);

	/* Copy the input */
	memcpy(workbuf, iname->name, iname->len);

	/* Initialize IV */
	memset(iv, 0, EXT4_CRYPTO_BLOCK_SIZE);

	/* Create encryption request */
	sg_init_table(sg, 1);
	sg_set_page(sg, ctx->workpage, PAGE_SIZE, 0);
	ablkcipher_request_set_crypt(req, sg, sg, iname->len, iv);
	res = crypto_ablkcipher_decrypt(req);
	if (res == -EINPROGRESS \|\| res == -EBUSY) {
	BUG_ON(req->base.data != &ecr);
	wait_for_completion(&ecr.completion);
	res = ecr.res;
	}
	if (res >= 0) {
	/* Copy the result to output */
	memcpy(oname->name, workbuf, iname->len);
	res = iname->len;
	}
	kunmap(ctx->workpage);
	ablkcipher_request_free(req);
	if (res < 0) {
	printk_ratelimited(
	KERN_ERR "%s: Error in ext4_fname_encrypt (error code %d)\n",
	__func__, res);
	return res;
	}

	oname->len = strnlen(oname->name, iname->len);
	return oname->len;
	}

	static const char *lookup_table =
	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";

	/**
	* ext4_fname_encode_digest() -
	*
	* Encodes the input digest using characters from the set [a-zA-Z0-9_+].
	* The encoded string is roughly 4/3 times the size of the input string.
	*/
	static int digest_encode(const char src, int len, char dst)
	{
	int i = 0, bits = 0, ac = 0;
	char *cp = dst;

	while (i < len) {
	ac += (((unsigned char) src[i]) << bits);
	bits += 8;
	do {
	*cp++ = lookup_table[ac & 0x3f];
	ac >>= 6;
	bits -= 6;
	} while (bits >= 6);
	i++;
	}
	if (bits)
	*cp++ = lookup_table[ac & 0x3f];
	return cp - dst;
	}

	static int digest_decode(const char src, int len, char dst)
	{
	int i = 0, bits = 0, ac = 0;
	const char *p;
	char *cp = dst;

	while (i < len) {
	p = strchr(lookup_table, src[i]);
	if (p == NULL \|\| src[i] == 0)
	return -2;
	ac += (p - lookup_table) << bits;
	bits += 6;
	if (bits >= 8) {
	*cp++ = ac & 0xff;
	ac >>= 8;
	bits -= 8;
	}
	i++;
	}
	if (ac)
	return -1;
	return cp - dst;
	}

	/**
	* ext4_free_fname_crypto_ctx() -
	*
	* Frees up a crypto context.
	*/
	void ext4_free_fname_crypto_ctx(struct ext4_fname_crypto_ctx *ctx)
	{
	if (ctx == NULL \|\| IS_ERR(ctx))
	return;

	if (ctx->ctfm && !IS_ERR(ctx->ctfm))
	crypto_free_ablkcipher(ctx->ctfm);
	if (ctx->htfm && !IS_ERR(ctx->htfm))
	crypto_free_hash(ctx->htfm);
	if (ctx->workpage && !IS_ERR(ctx->workpage))
	__free_page(ctx->workpage);
	kfree(ctx);
	}

	/**
	* ext4_put_fname_crypto_ctx() -
	*
	* Return: The crypto context onto free list. If the free list is above a
	* threshold, completely frees up the context, and returns the memory.
	*
	* TODO: Currently we directly free the crypto context. Eventually we should
	* add code it to return to free list. Such an approach will increase
	* efficiency of directory lookup.
	*/
	void ext4_put_fname_crypto_ctx(struct ext4_fname_crypto_ctx **ctx)
	{
	if (ctx == NULL \|\| IS_ERR(ctx))
	return;
	ext4_free_fname_crypto_ctx(*ctx);
	*ctx = NULL;
	}

	/**
	* ext4_search_fname_crypto_ctx() -
	*/
	static struct ext4_fname_crypto_ctx *ext4_search_fname_crypto_ctx(
	const struct ext4_encryption_key *key)
	{
	return NULL;
	}

	/**
	* ext4_alloc_fname_crypto_ctx() -
	*/
	struct ext4_fname_crypto_ctx *ext4_alloc_fname_crypto_ctx(
	const struct ext4_encryption_key *key)
	{
	struct ext4_fname_crypto_ctx *ctx;

	ctx = kmalloc(sizeof(struct ext4_fname_crypto_ctx), GFP_NOFS);
	if (ctx == NULL)
	return ERR_PTR(-ENOMEM);
	if (key->mode == EXT4_ENCRYPTION_MODE_INVALID) {
	/* This will automatically set key mode to invalid
	* As enum for ENCRYPTION_MODE_INVALID is zero */
	memset(&ctx->key, 0, sizeof(ctx->key));
	} else {
	memcpy(&ctx->key, key, sizeof(struct ext4_encryption_key));
	}
	ctx->has_valid_key = (EXT4_ENCRYPTION_MODE_INVALID == key->mode)
	? 0 : 1;
	ctx->ctfm_key_is_ready = 0;
	ctx->ctfm = NULL;
	ctx->htfm = NULL;
	ctx->workpage = NULL;
	return ctx;
	}

	/**
	* ext4_get_fname_crypto_ctx() -
	*
	* Allocates a free crypto context and initializes it to hold
	* the crypto material for the inode.
	*
	* Return: NULL if not encrypted. Error value on error. Valid pointer otherwise.
	*/
	struct ext4_fname_crypto_ctx *ext4_get_fname_crypto_ctx(
	struct inode *inode, u32 max_ciphertext_len)
	{
	struct ext4_fname_crypto_ctx *ctx;
	struct ext4_inode_info *ei = EXT4_I(inode);
	int res;

	/* Check if the crypto policy is set on the inode */
	res = ext4_encrypted_inode(inode);
	if (res == 0)
	return NULL;

	if (!ext4_has_encryption_key(inode))
	ext4_generate_encryption_key(inode);

	/* Get a crypto context based on the key.
	* A new context is allocated if no context matches the requested key.
	*/
	ctx = ext4_search_fname_crypto_ctx(&(ei->i_encryption_key));
	if (ctx == NULL)
	ctx = ext4_alloc_fname_crypto_ctx(&(ei->i_encryption_key));
	if (IS_ERR(ctx))
	return ctx;

	ctx->flags = ei->i_crypt_policy_flags;
	if (ctx->has_valid_key) {
	if (ctx->key.mode != EXT4_ENCRYPTION_MODE_AES_256_CTS) {
	printk_once(KERN_WARNING
	"ext4: unsupported key mode %d\n",
	ctx->key.mode);
	return ERR_PTR(-ENOKEY);
	}

	/* As a first cut, we will allocate new tfm in every call.
	* later, we will keep the tfm around, in case the key gets
	* re-used */
	if (ctx->ctfm == NULL) {
	ctx->ctfm = crypto_alloc_ablkcipher("cts(cbc(aes))",
	0, 0);
	}
	if (IS_ERR(ctx->ctfm)) {
	res = PTR_ERR(ctx->ctfm);
	printk(
	KERN_DEBUG "%s: error (%d) allocating crypto tfm\n",
	__func__, res);
	ctx->ctfm = NULL;
	ext4_put_fname_crypto_ctx(&ctx);
	return ERR_PTR(res);
	}
	if (ctx->ctfm == NULL) {
	printk(
	KERN_DEBUG "%s: could not allocate crypto tfm\n",
	__func__);
	ext4_put_fname_crypto_ctx(&ctx);
	return ERR_PTR(-ENOMEM);
	}
	if (ctx->workpage == NULL)
	ctx->workpage = alloc_page(GFP_NOFS);
	if (IS_ERR(ctx->workpage)) {
	res = PTR_ERR(ctx->workpage);
	printk(
	KERN_DEBUG "%s: error (%d) allocating work page\n",
	__func__, res);
	ctx->workpage = NULL;
	ext4_put_fname_crypto_ctx(&ctx);
	return ERR_PTR(res);
	}
	if (ctx->workpage == NULL) {
	printk(
	KERN_DEBUG "%s: could not allocate work page\n",
	__func__);
	ext4_put_fname_crypto_ctx(&ctx);
	return ERR_PTR(-ENOMEM);
	}
	ctx->lim = max_ciphertext_len;
	crypto_ablkcipher_clear_flags(ctx->ctfm, ~0);
	crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctx->ctfm),
	CRYPTO_TFM_REQ_WEAK_KEY);

	/* If we are lucky, we will get a context that is already
	* set up with the right key. Else, we will have to
	* set the key */
	if (!ctx->ctfm_key_is_ready) {
	/* Since our crypto objectives for filename encryption
	* are pretty weak,
	* we directly use the inode master key */
	res = crypto_ablkcipher_setkey(ctx->ctfm,
	ctx->key.raw, ctx->key.size);
	if (res) {
	ext4_put_fname_crypto_ctx(&ctx);
	return ERR_PTR(-EIO);
	}
	ctx->ctfm_key_is_ready = 1;
	} else {
	/* In the current implementation, key should never be
	* marked "ready" for a context that has just been
	* allocated. So we should never reach here */
	BUG();
	}
	}
	if (ctx->htfm == NULL)
	ctx->htfm = crypto_alloc_hash("sha256", 0, CRYPTO_ALG_ASYNC);
	if (IS_ERR(ctx->htfm)) {
	res = PTR_ERR(ctx->htfm);
	printk(KERN_DEBUG "%s: error (%d) allocating hash tfm\n",
	__func__, res);
	ctx->htfm = NULL;
	ext4_put_fname_crypto_ctx(&ctx);
	return ERR_PTR(res);
	}
	if (ctx->htfm == NULL) {
	printk(KERN_DEBUG "%s: could not allocate hash tfm\n",
	__func__);
	ext4_put_fname_crypto_ctx(&ctx);
	return ERR_PTR(-ENOMEM);
	}

	return ctx;
	}

	/**
	* ext4_fname_crypto_round_up() -
	*
	* Return: The next multiple of block size
	*/
	u32 ext4_fname_crypto_round_up(u32 size, u32 blksize)
	{
	return ((size+blksize-1)/blksize)*blksize;
	}

	/**
	* ext4_fname_crypto_namelen_on_disk() -
	*/
	int ext4_fname_crypto_namelen_on_disk(struct ext4_fname_crypto_ctx *ctx,
	u32 namelen)
	{
	u32 ciphertext_len;
	int padding = 4 << (ctx->flags & EXT4_POLICY_FLAGS_PAD_MASK);

	if (ctx == NULL)
	return -EIO;
	if (!(ctx->has_valid_key))
	return -EACCES;
	ciphertext_len = (namelen < EXT4_CRYPTO_BLOCK_SIZE) ?
	EXT4_CRYPTO_BLOCK_SIZE : namelen;
	ciphertext_len = ext4_fname_crypto_round_up(ciphertext_len, padding);
	ciphertext_len = (ciphertext_len > ctx->lim)
	? ctx->lim : ciphertext_len;
	return (int) ciphertext_len;
	}

	/**
	* ext4_fname_crypto_alloc_obuff() -
	*
	* Allocates an output buffer that is sufficient for the crypto operation
	* specified by the context and the direction.
	*/
	int ext4_fname_crypto_alloc_buffer(struct ext4_fname_crypto_ctx *ctx,
	u32 ilen, struct ext4_str *crypto_str)
	{
	unsigned int olen;
	int padding = 4 << (ctx->flags & EXT4_POLICY_FLAGS_PAD_MASK);

	if (!ctx)
	return -EIO;
	if (padding < EXT4_CRYPTO_BLOCK_SIZE)
	padding = EXT4_CRYPTO_BLOCK_SIZE;
	olen = ext4_fname_crypto_round_up(ilen, padding);
	crypto_str->len = olen;
	if (olen < EXT4_FNAME_CRYPTO_DIGEST_SIZE*2)
	olen = EXT4_FNAME_CRYPTO_DIGEST_SIZE*2;
	/* Allocated buffer can hold one more character to null-terminate the
	* string */
	crypto_str->name = kmalloc(olen+1, GFP_NOFS);
	if (!(crypto_str->name))
	return -ENOMEM;
	return 0;
	}

	/**
	* ext4_fname_crypto_free_buffer() -
	*
	* Frees the buffer allocated for crypto operation.
	*/
	void ext4_fname_crypto_free_buffer(struct ext4_str *crypto_str)
	{
	if (!crypto_str)
	return;
	kfree(crypto_str->name);
	crypto_str->name = NULL;
	}

	/**
	* ext4_fname_disk_to_usr() - converts a filename from disk space to user space
	*/
	int _ext4_fname_disk_to_usr(struct ext4_fname_crypto_ctx *ctx,
	struct dx_hash_info *hinfo,
	const struct ext4_str *iname,
	struct ext4_str *oname)
	{
	char buf[24];
	int ret;

	if (ctx == NULL)
	return -EIO;
	if (iname->len < 3) {
	/Check for . and .. /
	if (iname->name[0] == '.' && iname->name[iname->len-1] == '.') {
	oname->name[0] = '.';
	oname->name[iname->len-1] = '.';
	oname->len = iname->len;
	return oname->len;
	}
	}
	if (ctx->has_valid_key)
	return ext4_fname_decrypt(ctx, iname, oname);

	if (iname->len <= EXT4_FNAME_CRYPTO_DIGEST_SIZE) {
	ret = digest_encode(iname->name, iname->len, oname->name);
	oname->len = ret;
	return ret;
	}
	if (hinfo) {
	memcpy(buf, &hinfo->hash, 4);
	memcpy(buf+4, &hinfo->minor_hash, 4);
	} else
	memset(buf, 0, 8);
	memcpy(buf + 8, iname->name + iname->len - 16, 16);
	oname->name[0] = '_';
	ret = digest_encode(buf, 24, oname->name+1);
	oname->len = ret + 1;
	return ret + 1;
	}

	int ext4_fname_disk_to_usr(struct ext4_fname_crypto_ctx *ctx,
	struct dx_hash_info *hinfo,
	const struct ext4_dir_entry_2 *de,
	struct ext4_str *oname)
	{
	struct ext4_str iname = {.name = (unsigned char *) de->name,
	.len = de->name_len };

	return _ext4_fname_disk_to_usr(ctx, hinfo, &iname, oname);
	}


	/**
	* ext4_fname_usr_to_disk() - converts a filename from user space to disk space
	*/
	int ext4_fname_usr_to_disk(struct ext4_fname_crypto_ctx *ctx,
	const struct qstr *iname,
	struct ext4_str *oname)
	{
	int res;

	if (ctx == NULL)
	return -EIO;
	if (iname->len < 3) {
	/Check for . and .. /
	if (iname->name[0] == '.' &&
	iname->name[iname->len-1] == '.') {
	oname->name[0] = '.';
	oname->name[iname->len-1] = '.';
	oname->len = iname->len;
	return oname->len;
	}
	}
	if (ctx->has_valid_key) {
	res = ext4_fname_encrypt(ctx, iname, oname);
	return res;
	}
	/* Without a proper key, a user is not allowed to modify the filenames
	* in a directory. Consequently, a user space name cannot be mapped to
	* a disk-space name */
	return -EACCES;
	}

	/*
	* Calculate the htree hash from a filename from user space
	*/
	int ext4_fname_usr_to_hash(struct ext4_fname_crypto_ctx *ctx,
	const struct qstr *iname,
	struct dx_hash_info *hinfo)
	{
	struct ext4_str tmp;
	int ret = 0;
	char buf[EXT4_FNAME_CRYPTO_DIGEST_SIZE+1];

	if (!ctx \|\|
	((iname->name[0] == '.') &&
	((iname->len == 1) \|\|
	((iname->name[1] == '.') && (iname->len == 2))))) {
	ext4fs_dirhash(iname->name, iname->len, hinfo);
	return 0;
	}

	if (!ctx->has_valid_key && iname->name[0] == '_') {
	if (iname->len != 33)
	return -ENOENT;
	ret = digest_decode(iname->name+1, iname->len, buf);
	if (ret != 24)
	return -ENOENT;
	memcpy(&hinfo->hash, buf, 4);
	memcpy(&hinfo->minor_hash, buf + 4, 4);
	return 0;
	}

	if (!ctx->has_valid_key && iname->name[0] != '_') {
	if (iname->len > 43)
	return -ENOENT;
	ret = digest_decode(iname->name, iname->len, buf);
	ext4fs_dirhash(buf, ret, hinfo);
	return 0;
	}

	/* First encrypt the plaintext name */
	ret = ext4_fname_crypto_alloc_buffer(ctx, iname->len, &tmp);
	if (ret < 0)
	return ret;

	ret = ext4_fname_encrypt(ctx, iname, &tmp);
	if (ret >= 0) {
	ext4fs_dirhash(tmp.name, tmp.len, hinfo);
	ret = 0;
	}

	ext4_fname_crypto_free_buffer(&tmp);
	return ret;
	}

	int ext4_fname_match(struct ext4_fname_crypto_ctx ctx, struct ext4_str cstr,
	int len, const char * const name,
	struct ext4_dir_entry_2 *de)
	{
	int ret = -ENOENT;
	int bigname = (*name == '_');

	if (ctx->has_valid_key) {
	if (cstr->name == NULL) {
	struct qstr istr;

	ret = ext4_fname_crypto_alloc_buffer(ctx, len, cstr);
	if (ret < 0)
	goto errout;
	istr.name = name;
	istr.len = len;
	ret = ext4_fname_encrypt(ctx, &istr, cstr);
	if (ret < 0)
	goto errout;
	}
	} else {
	if (cstr->name == NULL) {
	cstr->name = kmalloc(32, GFP_KERNEL);
	if (cstr->name == NULL)
	return -ENOMEM;
	if ((bigname && (len != 33)) \|\|
	(!bigname && (len > 43)))
	goto errout;
	ret = digest_decode(name+bigname, len-bigname,
	cstr->name);
	if (ret < 0) {
	ret = -ENOENT;
	goto errout;
	}
	cstr->len = ret;
	}
	if (bigname) {
	if (de->name_len < 16)
	return 0;
	ret = memcmp(de->name + de->name_len - 16,
	cstr->name + 8, 16);
	return (ret == 0) ? 1 : 0;
	}
	}
	if (de->name_len != cstr->len)
	return 0;
	ret = memcmp(de->name, cstr->name, cstr->len);
	return (ret == 0) ? 1 : 0;
	errout:
	kfree(cstr->name);
	cstr->name = NULL;
	return ret;
	}