Re: [Xen-devel] xenstore test crash

[Rusty Russell <rusty@xxxxxxxxxxxxxxx>]

On Thu, 2005-06-09 at 22:21 -0500, Paul Larson wrote:
> Yeah, seemed odd to me too, but it was easily reproducible as long as I 
> was using --readonly.  Without the --readonly flag, the test passed with 
> no crash.

Untested code is buggy code.  Here's the patch (should apply with maybe
some minor fixups).

Rusty.

Index: xs_test.c
===================================================================
RCS file: /var/cvs/xeno-unstable/tools/xenstore/xs_test.c,v
retrieving revision 1.7
diff -u -r1.7 xs_test.c
--- xs_test.c   8 Jun 2005 09:06:12 -0000       1.7
+++ xs_test.c   10 Jun 2005 14:06:40 -0000
@@ -176,11 +176,11 @@
             "  watch <path> <token> <prio>\n"
             "  waitwatch\n"
             "  ackwatch <token>\n"
-            "  unwatch <path>\n"
+            "  unwatch <path> <token>\n"
             "  close\n"
             "  start <node>\n"
             "  abort\n"
-            "  introduce <domid> <mfn> <eventchn>\n"
+            "  introduce <domid> <mfn> <eventchn> <path>\n"
             "  commit\n"
             "  sleep <seconds>\n"
             "  dump\n");
Index: xsdaemon_core.c
===================================================================
RCS file: /var/cvs/xeno-unstable/tools/xenstore/xsdaemon_core.c,v
retrieving revision 1.25
diff -u -r1.25 xsdaemon_core.c
--- xsdaemon_core.c     9 Jun 2005 04:52:01 -0000       1.25
+++ xsdaemon_core.c     10 Jun 2005 14:06:41 -0000
@@ -645,7 +645,7 @@
                return false;
        }
 
-       if (!conn->write && (perm & XS_PERM_WRITE)) {
+       if (!conn->can_write && (perm & XS_PERM_WRITE)) {
                errno = EROFS;
                return false;
        }
@@ -972,9 +972,12 @@
                return do_set_perms(conn, in);
 
        case XS_SHUTDOWN:
+               /* FIXME: Implement gentle shutdown too. */
                /* Only tools can do this. */
                if (conn->id != 0)
                        return send_error(conn, EACCES);
+               if (!conn->can_write)
+                       return send_error(conn, EROFS);
                send_ack(conn, XS_SHUTDOWN);
                /* Everything hangs off auto-free context, freed at exit. */
                exit(0);
@@ -1173,6 +1176,7 @@
        new->transaction = NULL;
        new->write = write;
        new->read = read;
+       new->can_write = true;
 
        talloc_set_fail_handler(out_of_mem, &talloc_fail);
        if (setjmp(talloc_fail)) {
@@ -1206,10 +1210,11 @@
        if (fd < 0)
                return;
 
-       conn = new_connection(canwrite ? writefd : NULL, readfd);
-       if (conn)
+       conn = new_connection(writefd, readfd);
+       if (conn) {
                conn->fd = fd;
-       else
+               conn->can_write = canwrite;
+       } else
                close(fd);
 }
 
Index: xsdaemon_core.h
===================================================================
RCS file: /var/cvs/xeno-unstable/tools/xenstore/xsdaemon_core.h,v
retrieving revision 1.9
diff -u -r1.9 xsdaemon_core.h
--- xsdaemon_core.h     8 Jun 2005 09:06:12 -0000       1.9
+++ xsdaemon_core.h     10 Jun 2005 14:06:42 -0000
@@ -56,6 +56,9 @@
        /* Are we blocked waiting for a transaction to end?  Contains node. */
        char *blocked;
 
+       /* Is this a read-only connection? */
+       bool can_write;
+
        /* Are we waiting for a watch event ack? */
        bool waiting_for_ack;
 
Index: xsdaemon_domain.c
===================================================================
RCS file: /var/cvs/xeno-unstable/tools/xenstore/xsdaemon_domain.c,v
retrieving revision 1.16
diff -u -r1.16 xsdaemon_domain.c
--- xsdaemon_domain.c   6 Jun 2005 01:30:55 -0000       1.16
+++ xsdaemon_domain.c   10 Jun 2005 14:06:42 -0000
@@ -271,6 +271,9 @@
        if (conn->id != 0)
                return send_error(conn, EACCES);
 
+       if (!conn->can_write)
+               return send_error(conn, EROFS);
+
        /* Hang domain off "in" until we're finished. */
        domain = talloc(in, struct domain);
        domain->domid = atoi(vec[0]);

-- 
A bad analogy is like a leaky screwdriver -- Richard Braakman


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