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

[Chen Gang <gang.chen-bOixZGp5f+dBDgjK7y7TUQ@public.gmane.org>]

On 07/17/2013 09:58 AM, Scott Lovenberg wrote:
> On Tue, Jul 16, 2013 at 8:48 PM, 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..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.


Thank you very much.

-- 
Chen Gang