linux-kernel - Re: [PATCH 2/3] ecryptfs: Replace strcpy with strscpy in ecryptfs_cipher_code_to

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Message-ID: <aUsCpC_80ZCoUdDM@yaupon>
Date: Tue, 23 Dec 2025 14:59:16 -0600
From: Tyler Hicks <code@...icks.com>
To: Thorsten Blum <thorsten.blum@...ux.dev>
Cc: Eric Biggers <ebiggers@...nel.org>, Ard Biesheuvel <ardb@...nel.org>,
	Christian Brauner <brauner@...nel.org>,
	Al Viro <viro@...iv.linux.org.uk>, ecryptfs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] ecryptfs: Replace strcpy with strscpy in
 ecryptfs_cipher_code_to_string

On 2025-12-13 12:04:52, Thorsten Blum wrote:
> strcpy() has been deprecated [1] because it performs no bounds checking
> on the destination buffer, which can lead to buffer overflows. Since
> the parameter 'char *str' is just a pointer with no size information,
> extend the function with a 'size' parameter to pass the destination
> buffer's size as an additional argument. Adjust the call sites
> accordingly.
> 
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strcpy [1]
> Signed-off-by: Thorsten Blum <thorsten.blum@...ux.dev>

Acked-by: Tyler Hicks <code@...icks.com>

> ---
>  fs/ecryptfs/crypto.c          | 6 ++++--
>  fs/ecryptfs/ecryptfs_kernel.h | 2 +-
>  fs/ecryptfs/keystore.c        | 9 +++++++--
>  3 files changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
> index 2c37ee6a8be1..c99fc60a4e3b 100644
> --- a/fs/ecryptfs/crypto.c
> +++ b/fs/ecryptfs/crypto.c
> @@ -934,11 +934,12 @@ u8 ecryptfs_code_for_cipher_string(char *cipher_name, size_t key_bytes)
>  /**
>   * ecryptfs_cipher_code_to_string
>   * @str: Destination to write out the cipher name
> + * @size: Destination buffer size
>   * @cipher_code: The code to convert to cipher name string
>   *
>   * Returns zero on success
>   */
> -int ecryptfs_cipher_code_to_string(char *str, u8 cipher_code)
> +int ecryptfs_cipher_code_to_string(char *str, size_t size, u8 cipher_code)
>  {
>  	int rc = 0;
>  	int i;
> @@ -946,7 +947,8 @@ int ecryptfs_cipher_code_to_string(char *str, u8 cipher_code)
>  	str[0] = '\0';
>  	for (i = 0; i < ARRAY_SIZE(ecryptfs_cipher_code_str_map); i++)
>  		if (cipher_code == ecryptfs_cipher_code_str_map[i].cipher_code)
> -			strcpy(str, ecryptfs_cipher_code_str_map[i].cipher_str);
> +			strscpy(str, ecryptfs_cipher_code_str_map[i].cipher_str,
> +				size);
>  	if (str[0] == '\0') {
>  		ecryptfs_printk(KERN_WARNING, "Cipher code not recognized: "
>  				"[%d]\n", cipher_code);
> diff --git a/fs/ecryptfs/ecryptfs_kernel.h b/fs/ecryptfs/ecryptfs_kernel.h
> index 9e6ab0b41337..0d824350f31a 100644
> --- a/fs/ecryptfs/ecryptfs_kernel.h
> +++ b/fs/ecryptfs/ecryptfs_kernel.h
> @@ -577,7 +577,7 @@ int ecryptfs_read_and_validate_header_region(struct inode *inode);
>  int ecryptfs_read_and_validate_xattr_region(struct dentry *dentry,
>  					    struct inode *inode);
>  u8 ecryptfs_code_for_cipher_string(char *cipher_name, size_t key_bytes);
> -int ecryptfs_cipher_code_to_string(char *str, u8 cipher_code);
> +int ecryptfs_cipher_code_to_string(char *str, size_t size, u8 cipher_code);
>  void ecryptfs_set_default_sizes(struct ecryptfs_crypt_stat *crypt_stat);
>  int ecryptfs_generate_key_packet_set(char *dest_base,
>  				     struct ecryptfs_crypt_stat *crypt_stat,
> diff --git a/fs/ecryptfs/keystore.c b/fs/ecryptfs/keystore.c
> index 7f9f68c00ef6..b5204ab3150d 100644
> --- a/fs/ecryptfs/keystore.c
> +++ b/fs/ecryptfs/keystore.c
> @@ -954,7 +954,9 @@ ecryptfs_parse_tag_70_packet(char **filename, size_t *filename_size,
>  	s->fnek_sig_hex[ECRYPTFS_SIG_SIZE_HEX] = '\0';
>  	(*packet_size) += ECRYPTFS_SIG_SIZE;
>  	s->cipher_code = data[(*packet_size)++];
> -	rc = ecryptfs_cipher_code_to_string(s->cipher_string, s->cipher_code);
> +	rc = ecryptfs_cipher_code_to_string(s->cipher_string,
> +					    sizeof(s->cipher_string),
> +					    s->cipher_code);
>  	if (rc) {
>  		printk(KERN_WARNING "%s: Cipher code [%d] is invalid\n",
>  		       __func__, s->cipher_code);
> @@ -1172,7 +1174,9 @@ decrypt_pki_encrypted_session_key(struct ecryptfs_auth_tok *auth_tok,
>  	memcpy(crypt_stat->key, auth_tok->session_key.decrypted_key,
>  	       auth_tok->session_key.decrypted_key_size);
>  	crypt_stat->key_size = auth_tok->session_key.decrypted_key_size;
> -	rc = ecryptfs_cipher_code_to_string(crypt_stat->cipher, cipher_code);
> +	rc = ecryptfs_cipher_code_to_string(crypt_stat->cipher,
> +					    sizeof(crypt_stat->cipher),
> +					    cipher_code);
>  	if (rc) {
>  		ecryptfs_printk(KERN_ERR, "Cipher code [%d] is invalid\n",
>  				cipher_code);
> @@ -1438,6 +1442,7 @@ parse_tag_3_packet(struct ecryptfs_crypt_stat *crypt_stat,
>  		goto out_free;
>  	}
>  	rc = ecryptfs_cipher_code_to_string(crypt_stat->cipher,
> +					    sizeof(crypt_stat->cipher),
>  					    (u16)data[(*packet_size)]);
>  	if (rc)
>  		goto out_free;
> -- 
> Thorsten Blum <thorsten.blum@...ux.dev>
> GPG: 1D60 735E 8AEF 3BE4 73B6  9D84 7336 78FD 8DFE EAD4
>