cifs: dynamic allocation of ntlmssp blob

cifs: dynamic allocation of ntlmssp blob

commit b8da344b74c822e966c6d19d6b2321efe82c5d97 upstream.

In sess_auth_rawntlmssp_authenticate(), the ntlmssp blob is allocated
statically and its size is an "empirical" 5*sizeof(struct
_AUTHENTICATE_MESSAGE) (320B on x86_64). I don't know where this value
comes from or if it was ever appropriate, but it is currently
insufficient: the user and domain name in UTF16 could take 1kB by
themselves. Because of that, build_ntlmssp_auth_blob() might corrupt
memory (out-of-bounds write). The size of ntlmssp_blob in
SMB2_sess_setup() is too small too (sizeof(struct _NEGOTIATE_MESSAGE)
+ 500).

This patch allocates the blob dynamically in
build_ntlmssp_auth_blob().

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>
[bwh: Backported to 3.2:
 - Adjust context, indentation
 - build_ntlmssp_auth_blob() is static
 - Drop changes to smb2pdu.c
 - Use cERROR() instead of cifs_dbg(VFS, ...)
 - Use MAX_USERNAME_SIZE instead of CIFS_MAX_USERNAME_LEN]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>