CIFSSMBNegotiate(unsigned int xid, struct cifs_ses *ses)
{
	NEGOTIATE_REQ *pSMB;
	NEGOTIATE_RSP *pSMBr;
	int rc = 0;
	int bytes_returned;
	int i;
	struct TCP_Server_Info *server;
	u16 count;
	unsigned int secFlags;

	if (ses->server)
		server = ses->server;
	else {
		rc = -EIO;
		return rc;
	}
	rc = smb_init(SMB_COM_NEGOTIATE, 0, NULL /* no tcon yet */ ,
		      (void **) &pSMB, (void **) &pSMBr);
	if (rc)
		return rc;

	/* if any of auth flags (ie not sign or seal) are overriden use them */
	if (ses->overrideSecFlg & (~(CIFSSEC_MUST_SIGN | CIFSSEC_MUST_SEAL)))
		secFlags = ses->overrideSecFlg;  /* BB FIXME fix sign flags? */
	else /* if override flags set only sign/seal OR them with global auth */
		secFlags = global_secflags | ses->overrideSecFlg;

	cFYI(1, "secFlags 0x%x", secFlags);

	pSMB->hdr.Mid = GetNextMid(server);
	pSMB->hdr.Flags2 |= (SMBFLG2_UNICODE | SMBFLG2_ERR_STATUS);

	if ((secFlags & CIFSSEC_MUST_KRB5) == CIFSSEC_MUST_KRB5)
		pSMB->hdr.Flags2 |= SMBFLG2_EXT_SEC;
	else if ((secFlags & CIFSSEC_AUTH_MASK) == CIFSSEC_MAY_KRB5) {
		cFYI(1, "Kerberos only mechanism, enable extended security");
		pSMB->hdr.Flags2 |= SMBFLG2_EXT_SEC;
	} else if ((secFlags & CIFSSEC_MUST_NTLMSSP) == CIFSSEC_MUST_NTLMSSP)
		pSMB->hdr.Flags2 |= SMBFLG2_EXT_SEC;
	else if ((secFlags & CIFSSEC_AUTH_MASK) == CIFSSEC_MAY_NTLMSSP) {
		cFYI(1, "NTLMSSP only mechanism, enable extended security");
		pSMB->hdr.Flags2 |= SMBFLG2_EXT_SEC;
	}

	count = 0;
	for (i = 0; i < CIFS_NUM_PROT; i++) {
		strncpy(pSMB->DialectsArray+count, protocols[i].name, 16);
		count += strlen(protocols[i].name) + 1;
		/* null at end of source and target buffers anyway */
	}
	inc_rfc1001_len(pSMB, count);
	pSMB->ByteCount = cpu_to_le16(count);

	rc = SendReceive(xid, ses, (struct smb_hdr *) pSMB,
			 (struct smb_hdr *) pSMBr, &bytes_returned, 0);
	if (rc != 0)
		goto neg_err_exit;

	server->dialect = le16_to_cpu(pSMBr->DialectIndex);
	cFYI(1, "Dialect: %d", server->dialect);
	/* Check wct = 1 error case */
	if ((pSMBr->hdr.WordCount < 13) || (server->dialect == BAD_PROT)) {
		/* core returns wct = 1, but we do not ask for core - otherwise
		small wct just comes when dialect index is -1 indicating we
		could not negotiate a common dialect */
		rc = -EOPNOTSUPP;
		goto neg_err_exit;
#ifdef CONFIG_CIFS_WEAK_PW_HASH
	} else if ((pSMBr->hdr.WordCount == 13)
			&& ((server->dialect == LANMAN_PROT)
				|| (server->dialect == LANMAN2_PROT))) {
		__s16 tmp;
		struct lanman_neg_rsp *rsp = (struct lanman_neg_rsp *)pSMBr;

		if ((secFlags & CIFSSEC_MAY_LANMAN) ||
			(secFlags & CIFSSEC_MAY_PLNTXT))
			server->secType = LANMAN;
		else {
			cERROR(1, "mount failed weak security disabled"
				   " in /proc/fs/cifs/SecurityFlags");
			rc = -EOPNOTSUPP;
			goto neg_err_exit;
		}
		server->sec_mode = (__u8)le16_to_cpu(rsp->SecurityMode);
		server->maxReq = le16_to_cpu(rsp->MaxMpxCount);
		server->maxBuf = min((__u32)le16_to_cpu(rsp->MaxBufSize),
				(__u32)CIFSMaxBufSize + MAX_CIFS_HDR_SIZE);
		server->max_vcs = le16_to_cpu(rsp->MaxNumberVcs);
		/* even though we do not use raw we might as well set this
		accurately, in case we ever find a need for it */
		if ((le16_to_cpu(rsp->RawMode) & RAW_ENABLE) == RAW_ENABLE) {
			server->max_rw = 0xFF00;
			server->capabilities = CAP_MPX_MODE | CAP_RAW_MODE;
		} else {
			server->max_rw = 0;/* do not need to use raw anyway */
			server->capabilities = CAP_MPX_MODE;
		}
		tmp = (__s16)le16_to_cpu(rsp->ServerTimeZone);
		if (tmp == -1) {
			/* OS/2 often does not set timezone therefore
			 * we must use server time to calc time zone.
			 * Could deviate slightly from the right zone.
			 * Smallest defined timezone difference is 15 minutes
			 * (i.e. Nepal).  Rounding up/down is done to match
			 * this requirement.
			 */
			int val, seconds, remain, result;
			struct timespec ts, utc;
			utc = CURRENT_TIME;
			ts = cnvrtDosUnixTm(rsp->SrvTime.Date,
					    rsp->SrvTime.Time, 0);
			cFYI(1, "SrvTime %d sec since 1970 (utc: %d) diff: %d",
				(int)ts.tv_sec, (int)utc.tv_sec,
				(int)(utc.tv_sec - ts.tv_sec));
			val = (int)(utc.tv_sec - ts.tv_sec);
			seconds = abs(val);
			result = (seconds / MIN_TZ_ADJ) * MIN_TZ_ADJ;
			remain = seconds % MIN_TZ_ADJ;
			if (remain >= (MIN_TZ_ADJ / 2))
				result += MIN_TZ_ADJ;
			if (val < 0)
				result = -result;
			server->timeAdj = result;
		} else {
			server->timeAdj = (int)tmp;
			server->timeAdj *= 60; /* also in seconds */
		}
		cFYI(1, "server->timeAdj: %d seconds", server->timeAdj);


		/* BB get server time for time conversions and add
		code to use it and timezone since this is not UTC */

		if (rsp->EncryptionKeyLength ==
				cpu_to_le16(CIFS_CRYPTO_KEY_SIZE)) {
			memcpy(ses->server->cryptkey, rsp->EncryptionKey,
				CIFS_CRYPTO_KEY_SIZE);
		} else if (server->sec_mode & SECMODE_PW_ENCRYPT) {
			rc = -EIO; /* need cryptkey unless plain text */
			goto neg_err_exit;
		}

		cFYI(1, "LANMAN negotiated");
		/* we will not end up setting signing flags - as no signing
		was in LANMAN and server did not return the flags on */
		goto signing_check;
#else /* weak security disabled */
	} else if (pSMBr->hdr.WordCount == 13) {
		cERROR(1, "mount failed, cifs module not built "
			  "with CIFS_WEAK_PW_HASH support");
		rc = -EOPNOTSUPP;
#endif /* WEAK_PW_HASH */
		goto neg_err_exit;
	} else if (pSMBr->hdr.WordCount != 17) {
		/* unknown wct */
		rc = -EOPNOTSUPP;
		goto neg_err_exit;
	}
	/* else wct == 17 NTLM */
	server->sec_mode = pSMBr->SecurityMode;
	if ((server->sec_mode & SECMODE_USER) == 0)
		cFYI(1, "share mode security");

	if ((server->sec_mode & SECMODE_PW_ENCRYPT) == 0)
#ifdef CONFIG_CIFS_WEAK_PW_HASH
		if ((secFlags & CIFSSEC_MAY_PLNTXT) == 0)
#endif /* CIFS_WEAK_PW_HASH */
			cERROR(1, "Server requests plain text password"
				  " but client support disabled");

	if ((secFlags & CIFSSEC_MUST_NTLMV2) == CIFSSEC_MUST_NTLMV2)
		server->secType = NTLMv2;
	else if (secFlags & CIFSSEC_MAY_NTLM)
		server->secType = NTLM;
	else if (secFlags & CIFSSEC_MAY_NTLMV2)
		server->secType = NTLMv2;
	else if (secFlags & CIFSSEC_MAY_KRB5)
		server->secType = Kerberos;
	else if (secFlags & CIFSSEC_MAY_NTLMSSP)
		server->secType = RawNTLMSSP;
	else if (secFlags & CIFSSEC_MAY_LANMAN)
		server->secType = LANMAN;
	else {
		rc = -EOPNOTSUPP;
		cERROR(1, "Invalid security type");
		goto neg_err_exit;
	}
	/* else ... any others ...? */

	/* one byte, so no need to convert this or EncryptionKeyLen from
	   little endian */
	server->maxReq = le16_to_cpu(pSMBr->MaxMpxCount);
	/* probably no need to store and check maxvcs */
	server->maxBuf = min(le32_to_cpu(pSMBr->MaxBufferSize),
			(__u32) CIFSMaxBufSize + MAX_CIFS_HDR_SIZE);
	server->max_rw = le32_to_cpu(pSMBr->MaxRawSize);
	cFYI(DBG2, "Max buf = %d", ses->server->maxBuf);
	server->capabilities = le32_to_cpu(pSMBr->Capabilities);
	server->timeAdj = (int)(__s16)le16_to_cpu(pSMBr->ServerTimeZone);
	server->timeAdj *= 60;
	if (pSMBr->EncryptionKeyLength == CIFS_CRYPTO_KEY_SIZE) {
		memcpy(ses->server->cryptkey, pSMBr->u.EncryptionKey,
		       CIFS_CRYPTO_KEY_SIZE);
	} else if ((pSMBr->hdr.Flags2 & SMBFLG2_EXT_SEC ||
			server->capabilities & CAP_EXTENDED_SECURITY) &&
				(pSMBr->EncryptionKeyLength == 0)) {
		/* decode security blob */
		count = get_bcc(&pSMBr->hdr);
		if (count < 16) {
			rc = -EIO;
			goto neg_err_exit;
		}
		spin_lock(&cifs_tcp_ses_lock);
		if (server->srv_count > 1) {
			spin_unlock(&cifs_tcp_ses_lock);
			if (memcmp(server->server_GUID,
				   pSMBr->u.extended_response.
				   GUID, 16) != 0) {
				cFYI(1, "server UID changed");
				memcpy(server->server_GUID,
					pSMBr->u.extended_response.GUID,
					16);
			}
		} else {
			spin_unlock(&cifs_tcp_ses_lock);
			memcpy(server->server_GUID,
			       pSMBr->u.extended_response.GUID, 16);
		}

		if (count == 16) {
			server->secType = RawNTLMSSP;
		} else {
			rc = decode_negTokenInit(pSMBr->u.extended_response.
						 SecurityBlob, count - 16,
						 server);
			if (rc == 1)
				rc = 0;
			else
				rc = -EINVAL;
			if (server->secType == Kerberos) {
				if (!server->sec_kerberos &&
						!server->sec_mskerberos)
					rc = -EOPNOTSUPP;
			} else if (server->secType == RawNTLMSSP) {
				if (!server->sec_ntlmssp)
					rc = -EOPNOTSUPP;
			} else
					rc = -EOPNOTSUPP;
		}
	} else if (server->sec_mode & SECMODE_PW_ENCRYPT) {
		rc = -EIO; /* no crypt key only if plain text pwd */
		goto neg_err_exit;
	} else
		server->capabilities &= ~CAP_EXTENDED_SECURITY;

#ifdef CONFIG_CIFS_WEAK_PW_HASH
signing_check:
#endif
	if ((secFlags & CIFSSEC_MAY_SIGN) == 0) {
		/* MUST_SIGN already includes the MAY_SIGN FLAG
		   so if this is zero it means that signing is disabled */
		cFYI(1, "Signing disabled");
		if (server->sec_mode & SECMODE_SIGN_REQUIRED) {
			cERROR(1, "Server requires "
				   "packet signing to be enabled in "
				   "/proc/fs/cifs/SecurityFlags.");
			rc = -EOPNOTSUPP;
		}
		server->sec_mode &=
			~(SECMODE_SIGN_ENABLED | SECMODE_SIGN_REQUIRED);
	} else if ((secFlags & CIFSSEC_MUST_SIGN) == CIFSSEC_MUST_SIGN) {
		/* signing required */
		cFYI(1, "Must sign - secFlags 0x%x", secFlags);
		if ((server->sec_mode &
			(SECMODE_SIGN_ENABLED | SECMODE_SIGN_REQUIRED)) == 0) {
			cERROR(1, "signing required but server lacks support");
			rc = -EOPNOTSUPP;
		} else
			server->sec_mode |= SECMODE_SIGN_REQUIRED;
	} else {
		/* signing optional ie CIFSSEC_MAY_SIGN */
		if ((server->sec_mode & SECMODE_SIGN_REQUIRED) == 0)
			server->sec_mode &=
				~(SECMODE_SIGN_ENABLED | SECMODE_SIGN_REQUIRED);
	}

neg_err_exit:
	cifs_buf_release(pSMB);

	cFYI(1, "negprot rc %d", rc);
	return rc;
}

This weakness involves numeric computation errors, such as integer overflows, underflows, or precision losses, which can lead to miscalculations and exploitable behaviors in software.