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

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On Tue, Jul 16, 2013 at 8:48 PM, Chen Gang <gang.chen@xxxxxxxxxxx> 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@xxxxxxxxxxx>
> ---
>  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..ce2d331 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_CIF_DOMAINNAME)
>                                 break;
>                         if (!ses->domainName) {
>                                 ses->domainName =
> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
> index 33f17ed..88280e0 100644
> --- a/fs/cifs/cifsglob.h
> +++ b/fs/cifs/cifsglob.h
> @@ -396,6 +396,7 @@ struct smb_version_values {
>
>  #define HEADER_SIZE(server) (server->vals->header_size)
>  #define MAX_HEADER_SIZE(server) (server->vals->max_header_size)
> +#define MAX_CIF_DOMAINNAME 256 /* 255 + '\0' */
>
>  struct smb_vol {
>         char *username;
> diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
> index fa68813..ed6bf20 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_CIF_DOMAINNAME)
> +                                       == MAX_CIF_DOMAINNAME) {
>                                 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_CIF_DOMAINNAME + 1 */
> +#define CIFSCREDS_DESC_SIZE (7 + MAX_CIF_DOMAINNAME + 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..106a575 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_CIF_DOMAINNAME, 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_CIF_DOMAINNAME);
> +               bcc_ptr += strnlen(ses->domainName, MAX_CIF_DOMAINNAME);
>         } /* else we will send a null domain name
>              so the server will default to its own domain */
>         *bcc_ptr = 0;
> --
> 1.7.7.6
> --
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If this is correct for the domain size, MAX_DOMAIN_SIZE in the
cifs-utils mount helper (mount.cifs.c) has to be changed.  It is
currently 64 + null terminator.  I can open a bug and patch it if this
is correct.

CC'ing Jeff Layton since he maintains the cifs-utils package.

--
Peace and Blessings,
-Scott.
--
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