Merge tag '9p-for-4.21' of git://github.com/martinetd/linux

Pull 9p updates from Dominique Martinet:
"Missing prototype warning fix and a syzkaller fix when a 9p server
advertises a too small msize"

* tag '9p-for-4.21' of git://github.com/martinetd/linux:
9p/net: put a lower bound on msize
net/9p: include trans_common.h to fix missing prototype warning.

net/9p/client.c

···
 				ret = r;
 				continue;
 			}
+			if (option < 4096) {
+				p9_debug(P9_DEBUG_ERROR,
+					 "msize should be at least 4k\n");
+				ret = -EINVAL;
+				continue;
+			}
 			clnt->msize = option;
 			break;
 		case Opt_trans:
···
 	else if (!strncmp(version, "9P2000", 6))
 		c->proto_version = p9_proto_legacy;
 	else {
+		p9_debug(P9_DEBUG_ERROR,
+			 "server returned an unknown version: %s\n", version);
 		err = -EREMOTEIO;
 		goto error;
 	}
 
+	if (msize < 4096) {
+		p9_debug(P9_DEBUG_ERROR,
+			 "server returned a msize < 4096: %d\n", msize);
+		err = -EREMOTEIO;
+		goto error;
+	}
 	if (msize < c->msize)
 		c->msize = msize;
 
···
 
 	if (clnt->msize > clnt->trans_mod->maxsize)
 		clnt->msize = clnt->trans_mod->maxsize;
+
+	if (clnt->msize < 4096) {
+		p9_debug(P9_DEBUG_ERROR,
+			 "Please specify a msize of at least 4k\n");
+		err = -EINVAL;
+		goto free_client;
+	}
 
 	err = p9_client_version(clnt);
 	if (err)

net/9p/trans_common.c

···
 
 #include <linux/mm.h>
 #include <linux/module.h>
+#include "trans_common.h"
 
 /**
  *  p9_release_pages - Release pages after the transaction.