cifs: we do not allow changing username/password/unc/... during remount

Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/cifsfs.c

@@ -493,7 +493,7 @@ cifs_show_options(struct seq_file *s, struct dentry *root)
 
 	if (tcon->no_lease)
 		seq_puts(s, ",nolease");
-	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MULTIUSER)
+	if (cifs_sb->ctx->multiuser)
 		seq_puts(s, ",multiuser");
 	else if (tcon->ses->user_name)
 		seq_show_option(s, "username", tcon->ses->user_name);

fs/cifs/fs_context.c

@@ -632,10 +632,51 @@ static int smb3_verify_reconfigure_ctx(struct smb3_fs_context *new_ctx,
 		cifs_dbg(VFS, "can not change sec during remount\n");
 		return -EINVAL;
 	}
+	if (new_ctx->multiuser != old_ctx->multiuser) {
+		cifs_dbg(VFS, "can not change multiuser during remount\n");
+		return -EINVAL;
+	}
+	if (new_ctx->UNC &&
+	    (!old_ctx->UNC || strcmp(new_ctx->UNC, old_ctx->UNC))) {
+		cifs_dbg(VFS, "can not change UNC during remount\n");
+		return -EINVAL;
+	}
+	if (new_ctx->username &&
+	    (!old_ctx->username || strcmp(new_ctx->username, old_ctx->username))) {
+		cifs_dbg(VFS, "can not change username during remount\n");
+		return -EINVAL;
+	}
+	if (new_ctx->password &&
+	    (!old_ctx->password || strcmp(new_ctx->password, old_ctx->password))) {
+		cifs_dbg(VFS, "can not change password during remount\n");
+		return -EINVAL;
+	}
+	if (new_ctx->domainname &&
+	    (!old_ctx->domainname || strcmp(new_ctx->domainname, old_ctx->domainname))) {
+		cifs_dbg(VFS, "can not change domainname during remount\n");
+		return -EINVAL;
+	}
+	if (new_ctx->nodename &&
+	    (!old_ctx->nodename || strcmp(new_ctx->nodename, old_ctx->nodename))) {
+		cifs_dbg(VFS, "can not change nodename during remount\n");
+		return -EINVAL;
+	}
+	if (new_ctx->iocharset &&
+	    (!old_ctx->iocharset || strcmp(new_ctx->iocharset, old_ctx->iocharset))) {
+		cifs_dbg(VFS, "can not change iocharset during remount\n");
+		return -EINVAL;
+	}
 
 	return 0;
 }
 
+#define STEAL_STRING(cifs_sb, ctx, field)				\
+do {									\
+	kfree(ctx->field);						\
+	ctx->field = cifs_sb->ctx->field;				\
+	cifs_sb->ctx->field = NULL;					\
+} while (0)
+
 static int smb3_reconfigure(struct fs_context *fc)
 {
 	struct smb3_fs_context *ctx = smb3_fc2context(fc);
@@ -648,10 +689,16 @@ static int smb3_reconfigure(struct fs_context *fc)
 		return rc;
 
 	/*
-	 * Steal the UNC from the old and to be destroyed context.
+	 * We can not change UNC/username/password/domainname/nodename/iocharset
+	 * during reconnect so ignore what we have in the new context and
+	 * just use what we already have in cifs_sb->ctx.
 	 */
-	ctx->UNC = cifs_sb->ctx->UNC;
+	STEAL_STRING(cifs_sb, ctx, UNC);
-	cifs_sb->ctx->UNC = NULL;
+	STEAL_STRING(cifs_sb, ctx, username);
+	STEAL_STRING(cifs_sb, ctx, password);
+	STEAL_STRING(cifs_sb, ctx, domainname);
+	STEAL_STRING(cifs_sb, ctx, nodename);
+	STEAL_STRING(cifs_sb, ctx, iocharset);
 
 	smb3_cleanup_fs_context_contents(cifs_sb->ctx);
 	rc = smb3_fs_context_dup(cifs_sb->ctx, ctx);

fs/cifs/fs_context.h

@@ -149,7 +149,6 @@ struct smb3_fs_context {
 	bool uid_specified;
 	bool gid_specified;
 	bool sloppy;
-	char *nodename;
 	bool got_ip;
 	bool got_version;
 	bool got_rsize;
@@ -161,6 +160,7 @@ struct smb3_fs_context {
 	char *password;
 	char *domainname;
 	char *UNC;
+	char *nodename;
 	char *iocharset;  /* local code page for mapping to and from Unicode */
 	char source_rfc1001_name[RFC1001_NAME_LEN_WITH_NULL]; /* clnt nb name */
 	char target_rfc1001_name[RFC1001_NAME_LEN_WITH_NULL]; /* srvr nb name */