commit 2ca8ede24ada82f22a77ab172a0a8214f623dc94
from: Fazlul Shahriar <fshahriar@gmail.com>
via: Dan Cross <crossd@gmail.com>
date: Tue Jul 26 16:11:38 2022 UTC

fossil: fix EOF detection when reading 9P message

When the 9P connection is closed, reads on the connection will keep
returning 0. So, fossil ends up looping forever, trying to read a 9P
message, consuming 100% CPU. The fix interprets 0 bytes read as EOF.

Reproduce by killing the 9pserve process serving the fossil service, or
by listening on tcp and using 9p(1).

commit - 23420c24937a8899bf1cfb900b9a5155b6f924ae
commit + 2ca8ede24ada82f22a77ab172a0a8214f623dc94
blob - 23da4f4ef665f1c2af5b2fafe16a5af6f8564efd
blob + d31a74265b7a2d97fec71de6fdfbc8590469b7ad
--- src/cmd/fossil/9proc.c
+++ src/cmd/fossil/9proc.c
@@ -362,9 +362,8 @@ msgRead(void* v)
 	while(!eof){
 		m = msgAlloc(con);
 
-		while((n = read9pmsg(fd, m->data, con->msize)) == 0)
-			;
-		if(n < 0){
+		n = read9pmsg(fd, m->data, con->msize);
+		if(n <= 0){
 			m->t.type = Tversion;
 			m->t.fid = NOFID;
 			m->t.tag = NOTAG;