smb3.1.1: allow dumping keys for multiuser mounts

When mounted multiuser it is hard to dump keys for the other sessions
which makes it hard to debug using network traces (e.g. using wireshark).
Suggested-by: NShyam Prasad N <sprasad@microsoft.com>
Reviewed-by: NShyam Prasad N <sprasad@microsoft.com>
Signed-off-by: NSteve French <stfrench@microsoft.com>

fs/cifs/ioctl.c

@@ -214,11 +214,54 @@ static int cifs_shutdown(struct super_block *sb, unsigned long arg)
 	return 0;
 }
 
+static int cifs_dump_full_key(struct cifs_tcon *tcon, unsigned long arg)
+{
+	struct smb3_full_key_debug_info pfull_key_inf;
+	__u64 suid;
+	struct list_head *tmp;
+	struct cifs_ses *ses;
+	bool found = false;
+
+	if (!smb3_encryption_required(tcon))
+		return -EOPNOTSUPP;
+
+	ses = tcon->ses; /* default to user id for current user */
+	if (get_user(suid, (__u64 __user *)arg))
+		suid = 0;
+	if (suid) {
+		/* search to see if there is a session with a matching SMB UID */
+		spin_lock(&cifs_tcp_ses_lock);
+		list_for_each(tmp, &tcon->ses->server->smb_ses_list) {
+			ses = list_entry(tmp, struct cifs_ses, smb_ses_list);
+			if (ses->Suid == suid) {
+				found = true;
+				break;
+			}
+		}
+		spin_unlock(&cifs_tcp_ses_lock);
+		if (found == false)
+			return -EINVAL;
+	} /* else uses default user's SMB UID (ie current user) */
+
+	pfull_key_inf.cipher_type = le16_to_cpu(ses->server->cipher_type);
+	pfull_key_inf.Suid = ses->Suid;
+	memcpy(pfull_key_inf.auth_key, ses->auth_key.response,
+	       16 /* SMB2_NTLMV2_SESSKEY_SIZE */);
+	memcpy(pfull_key_inf.smb3decryptionkey, ses->smb3decryptionkey,
+	       32 /* SMB3_ENC_DEC_KEY_SIZE */);
+	memcpy(pfull_key_inf.smb3encryptionkey,
+	       ses->smb3encryptionkey, 32 /* SMB3_ENC_DEC_KEY_SIZE */);
+	if (copy_to_user((void __user *)arg, &pfull_key_inf,
+			 sizeof(struct smb3_full_key_debug_info)))
+		return -EFAULT;
+
+	return 0;
+}
+
 long cifs_ioctl(struct file *filep, unsigned int command, unsigned long arg)
 {
 	struct inode *inode = file_inode(filep);
 	struct smb3_key_debug_info pkey_inf;
-	struct smb3_full_key_debug_info pfull_key_inf;
 	int rc = -ENOTTY; /* strange error - but the precedent */
 	unsigned int xid;
 	struct cifsFileInfo *pSMBFile = filep->private_data;
@@ -366,26 +409,9 @@ long cifs_ioctl(struct file *filep, unsigned int command, unsigned long arg)
 				rc = -EACCES;
 				break;
 			}
-
 			tcon = tlink_tcon(pSMBFile->tlink);
-			if (!smb3_encryption_required(tcon)) {
-				rc = -EOPNOTSUPP;
-				break;
-			}
-			pfull_key_inf.cipher_type =
-				le16_to_cpu(tcon->ses->server->cipher_type);
-			pfull_key_inf.Suid = tcon->ses->Suid;
-			memcpy(pfull_key_inf.auth_key, tcon->ses->auth_key.response,
-					16 /* SMB2_NTLMV2_SESSKEY_SIZE */);
-			memcpy(pfull_key_inf.smb3decryptionkey,
-			      tcon->ses->smb3decryptionkey, 32 /* SMB3_ENC_DEC_KEY_SIZE */);
-			memcpy(pfull_key_inf.smb3encryptionkey,
-			      tcon->ses->smb3encryptionkey, 32 /* SMB3_ENC_DEC_KEY_SIZE */);
-			if (copy_to_user((void __user *)arg, &pfull_key_inf,
-					sizeof(struct smb3_full_key_debug_info)))
-				rc = -EFAULT;
-			else
-				rc = 0;
+			rc = cifs_dump_full_key(tcon, arg);
+
 			break;
 		case CIFS_IOC_NOTIFY:
 			if (!S_ISDIR(inode->i_mode)) {