cifs: Fix use-after-free in SMB2_read

There is a KASAN use-after-free:
BUG: KASAN: use-after-free in SMB2_read+0x1136/0x1190
Read of size 8 at addr ffff8880b4e45e50 by task ln/1009

Should not release the 'req' because it will use in the trace.

Fixes: eccb4422cf97 ("smb3: Add ftrace tracepoints for improved SMB3 debugging")

Signed-off-by: ZhangXiaoxu <zhangxiaoxu5@huawei.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
CC: Stable <stable@vger.kernel.org> 4.18+
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
build_encrypt_ctxt(struct smb2_encryption_neg_context *pneg_ctxt)
{
	pneg_ctxt->ContextType = SMB2_ENCRYPTION_CAPABILITIES;
	pneg_ctxt->DataLength = cpu_to_le16(4); /* Cipher Count + le16 cipher */
	pneg_ctxt->CipherCount = cpu_to_le16(1);
/* pneg_ctxt->Ciphers[0] = SMB2_ENCRYPTION_AES128_GCM;*/ /* not supported yet */
	pneg_ctxt->Ciphers[0] = SMB2_ENCRYPTION_AES128_CCM;
}

build_encrypt_ctxt(struct smb2_encryption_neg_context *pneg_ctxt)
{
	pneg_ctxt->ContextType = SMB2_ENCRYPTION_CAPABILITIES;
	pneg_ctxt->DataLength = cpu_to_le16(4); /* Cipher Count + le16 cipher */
	pneg_ctxt->CipherCount = cpu_to_le16(1);
/* pneg_ctxt->Ciphers[0] = SMB2_ENCRYPTION_AES128_GCM;*/ /* not supported yet */
	pneg_ctxt->Ciphers[0] = SMB2_ENCRYPTION_AES128_CCM;
}
