Re: [PATCH v2] cifs: extend the buffer length enought for sprintf() using

[Jeff Layton <jlayton-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

On Fri, 19 Jul 2013 09:01:36 +0800
Chen Gang <gang.chen-bOixZGp5f+dBDgjK7y7TUQ@public.gmane.org> wrote:

> For cifs_set_cifscreds() in "fs/cifs/connect.c", 'desc' buffer length
> is 'CIFSCREDS_DESC_SIZE' (56 is less than 256), and 'ses->domainName'
> length may be "255 + '\0'".
> 
> The related sprintf() may cause memory overflow, so need extend related
> buffer enough to hold all things.
> 
> It is also necessary to be sure of 'ses->domainName' must be less than
> 256, and define the related macro instead of hard code number '256'.
> 
> Signed-off-by: Chen Gang <gang.chen-bOixZGp5f+dBDgjK7y7TUQ@public.gmane.org>
> ---
>  fs/cifs/cifsencrypt.c |    2 +-
>  fs/cifs/cifsglob.h    |    1 +
>  fs/cifs/connect.c     |    7 ++++---
>  fs/cifs/sess.c        |    6 +++---
>  4 files changed, 9 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c
> index 45e57cc..bb84d7c 100644
> --- a/fs/cifs/cifsencrypt.c
> +++ b/fs/cifs/cifsencrypt.c
> @@ -421,7 +421,7 @@ find_domain_name(struct cifs_ses *ses, const struct nls_table *nls_cp)
>  		if (blobptr + attrsize > blobend)
>  			break;
>  		if (type == NTLMSSP_AV_NB_DOMAIN_NAME) {
> -			if (!attrsize)
> +			if (!attrsize || attrsize >= MAX_DOMAINNAME_SIZE)
>  				break;
>  			if (!ses->domainName) {
>  				ses->domainName =
> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
> index 33f17ed..64bb4c5 100644
> --- a/fs/cifs/cifsglob.h
> +++ b/fs/cifs/cifsglob.h
> @@ -44,6 +44,7 @@
>  #define MAX_TREE_SIZE (2 + MAX_SERVER_SIZE + 1 + MAX_SHARE_SIZE + 1)
>  #define MAX_SERVER_SIZE 15
>  #define MAX_SHARE_SIZE 80
> +#define MAX_DOMAINNAME_SIZE 256	/* maximum fully qualified domain name (FQDN) */
>  #define MAX_USERNAME_SIZE 256	/* reasonable maximum for current servers */
>  #define MAX_PASSWORD_SIZE 512	/* max for windows seems to be 256 wide chars */
>  
> diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
> index fa68813..3f9dcf7 100644
> --- a/fs/cifs/connect.c
> +++ b/fs/cifs/connect.c
> @@ -1675,7 +1675,8 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
>  			if (string == NULL)
>  				goto out_nomem;
>  
> -			if (strnlen(string, 256) == 256) {
> +			if (strnlen(string, MAX_DOMAINNAME_SIZE)
> +					== MAX_DOMAINNAME_SIZE) {
>  				printk(KERN_WARNING "CIFS: domain name too"
>  						    " long\n");
>  				goto cifs_parse_mount_err;
> @@ -2276,8 +2277,8 @@ cifs_put_smb_ses(struct cifs_ses *ses)
>  
>  #ifdef CONFIG_KEYS
>  
> -/* strlen("cifs:a:") + INET6_ADDRSTRLEN + 1 */
> -#define CIFSCREDS_DESC_SIZE (7 + INET6_ADDRSTRLEN + 1)
> +/* strlen("cifs:a:") + MAX_DOMAINNAME_SIZE + 1 */
> +#define CIFSCREDS_DESC_SIZE (7 + MAX_DOMAINNAME_SIZE + 1)
>  
>  /* Populate username and pw fields from keyring if possible */
>  static int
> diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c
> index 79358e3..57b1537 100644
> --- a/fs/cifs/sess.c
> +++ b/fs/cifs/sess.c
> @@ -197,7 +197,7 @@ static void unicode_domain_string(char **pbcc_area, struct cifs_ses *ses,
>  		bytes_ret = 0;
>  	} else
>  		bytes_ret = cifs_strtoUTF16((__le16 *) bcc_ptr, ses->domainName,
> -					    256, nls_cp);
> +					    MAX_DOMAINNAME_SIZE, nls_cp);
>  	bcc_ptr += 2 * bytes_ret;
>  	bcc_ptr += 2;  /* account for null terminator */
>  
> @@ -255,8 +255,8 @@ static void ascii_ssetup_strings(char **pbcc_area, struct cifs_ses *ses,
>  
>  	/* copy domain */
>  	if (ses->domainName != NULL) {
> -		strncpy(bcc_ptr, ses->domainName, 256);
> -		bcc_ptr += strnlen(ses->domainName, 256);
> +		strncpy(bcc_ptr, ses->domainName, MAX_DOMAINNAME_SIZE);
> +		bcc_ptr += strnlen(ses->domainName, MAX_DOMAINNAME_SIZE);
>  	} /* else we will send a null domain name
>  	     so the server will default to its own domain */
>  	*bcc_ptr = 0;

Looks good...

Reviewed-by: Jeff Layton <jlayton-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>