[PATCH] ecryptfs: replace ecryptfs_from_hex() with hex2bin()

[Drif Abdelmalek Mohamed Said <drifabdelmalekmohamedsaid@gmail.com>]

ecryptfs_from_hex() relied on the deprecated simple_strtoul(). Rather
than patching it to use kstrtoul(), its intended replacement, remove it
entirely and switch all call sites to the generic hex2bin() helper
from <linux/hex.h>, which already provides the same functionality.

Update call sites with the (u8 *) casts required by hex2bin()'s
signature.

All call sites guarantee src is composed only of valid hex characters
and that src is at least 2*dst_size bytes, so hex2bin()'s stricter
error handling is never triggered here.

Signed-off-by: Drif Abdelmalek Mohamed Said <drifabdelmalekmohamedsaid@gmail.com>
---
 fs/ecryptfs/crypto.c          | 18 ------------------
 fs/ecryptfs/ecryptfs_kernel.h |  1 -
 fs/ecryptfs/keystore.c        |  7 ++++---
 3 files changed, 4 insertions(+), 22 deletions(-)

diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
index e67119b6029c..7e802fd631a6 100644
--- a/fs/ecryptfs/crypto.c
+++ b/fs/ecryptfs/crypto.c
@@ -29,24 +29,6 @@
 #define DECRYPT		0
 #define ENCRYPT		1
 
-/**
- * ecryptfs_from_hex
- * @dst: Buffer to take the bytes from src hex; must be at least of
- *       size (src_size / 2)
- * @src: Buffer to be converted from a hex string representation to raw value
- * @dst_size: size of dst buffer, or number of hex characters pairs to convert
- */
-void ecryptfs_from_hex(char *dst, char *src, int dst_size)
-{
-	int x;
-	char tmp[3] = { 0, };
-
-	for (x = 0; x < dst_size; x++) {
-		tmp[0] = src[x * 2];
-		tmp[1] = src[x * 2 + 1];
-		dst[x] = (unsigned char)simple_strtol(tmp, NULL, 16);
-	}
-}
 
 static int ecryptfs_crypto_api_algify_cipher_name(char **algified_name,
 						  const char *cipher_name,
diff --git a/fs/ecryptfs/ecryptfs_kernel.h b/fs/ecryptfs/ecryptfs_kernel.h
index 58165928ed1e..be91f7c3fc58 100644
--- a/fs/ecryptfs/ecryptfs_kernel.h
+++ b/fs/ecryptfs/ecryptfs_kernel.h
@@ -47,7 +47,6 @@ ecryptfs_to_hex(char *dst, char *src, size_t src_size)
 	*end = '\0';
 }
 
-extern void ecryptfs_from_hex(char *dst, char *src, int dst_size);
 
 struct ecryptfs_key_record {
 	unsigned char type;
diff --git a/fs/ecryptfs/keystore.c b/fs/ecryptfs/keystore.c
index 51651314b7a6..dcfb2e5fa88e 100644
--- a/fs/ecryptfs/keystore.c
+++ b/fs/ecryptfs/keystore.c
@@ -18,6 +18,7 @@
 #include <linux/random.h>
 #include <linux/scatterlist.h>
 #include <linux/slab.h>
+#include <linux/hex.h>
 #include "ecryptfs_kernel.h"
 
 /*
@@ -713,7 +714,7 @@ ecryptfs_write_tag_70_packet(char *dest, size_t *remaining_bytes,
 		goto out_free_unlock;
 	}
 	s->i += s->packet_size_len;
-	ecryptfs_from_hex(&dest[s->i],
+	hex2bin((u8 *)&dest[s->i],
 			  mount_crypt_stat->global_default_fnek_sig,
 			  ECRYPTFS_SIG_SIZE);
 	s->i += ECRYPTFS_SIG_SIZE;
@@ -2015,7 +2016,7 @@ write_tag_1_packet(char *dest, size_t *remaining_bytes,
 	int rc = 0;
 
 	(*packet_size) = 0;
-	ecryptfs_from_hex(key_rec->sig, auth_tok->token.private_key.signature,
+	hex2bin((u8 *)key_rec->sig, auth_tok->token.private_key.signature,
 			  ECRYPTFS_SIG_SIZE);
 	encrypted_session_key_valid = 0;
 	for (i = 0; i < crypt_stat->key_size; i++)
@@ -2179,7 +2180,7 @@ write_tag_3_packet(char *dest, size_t *remaining_bytes,
 	int rc = 0;
 
 	(*packet_size) = 0;
-	ecryptfs_from_hex(key_rec->sig, auth_tok->token.password.signature,
+	hex2bin((u8 *)key_rec->sig, auth_tok->token.password.signature,
 			  ECRYPTFS_SIG_SIZE);
 	rc = ecryptfs_get_tfm_and_mutex_for_cipher_name(&tfm, &tfm_mutex,
 							crypt_stat->cipher);
-- 
2.43.0