[src/trunk]: src/usr.sbin/puffs/mount_9p mount_9p: fix writing to a file open...

[ozaki-r <ozaki-r%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/89f70d3df0b8
branches:  trunk
changeset: 362480:89f70d3df0b8
user:      ozaki-r <ozaki-r%NetBSD.org@localhost>
date:      Wed Mar 02 04:11:41 2022 +0000

description:
mount_9p: fix writing to a file opened with write-only mode

With the page cache, writing data to a file may demand to read contents
from a storage to fill a page in the page cache first.

Opening a file with write-only mode by a user lets a mount_9p process
open a file with write-only mode too at a 9p server.  Thus, a read
request to the file from the page cache fails.

So we need to open a file always with read mode (internally) even if it
is opened with write-only mode by a user.

Note that the change doesn't mean that mount_9p allows users to read
contents from a file that is opened with write-only mode.

diffstat:

 usr.sbin/puffs/mount_9p/node.c |  6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diffs (27 lines):

diff -r 9f0328bed080 -r 89f70d3df0b8 usr.sbin/puffs/mount_9p/node.c
--- a/usr.sbin/puffs/mount_9p/node.c    Wed Mar 02 01:55:18 2022 +0000
+++ b/usr.sbin/puffs/mount_9p/node.c    Wed Mar 02 04:11:41 2022 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: node.c,v 1.29 2020/06/01 13:30:52 uwe Exp $    */
+/*     $NetBSD: node.c,v 1.30 2022/03/02 04:11:41 ozaki-r Exp $        */
 
 /*
  * Copyright (c) 2007  Antti Kantee.  All Rights Reserved.
@@ -27,7 +27,7 @@
 
 #include <sys/cdefs.h>
 #ifndef lint
-__RCSID("$NetBSD: node.c,v 1.29 2020/06/01 13:30:52 uwe Exp $");
+__RCSID("$NetBSD: node.c,v 1.30 2022/03/02 04:11:41 ozaki-r Exp $");
 #endif /* !lint */
 
 #include <assert.h>
@@ -274,6 +274,8 @@
 
        puffs_setback(pcc, PUFFS_SETBACK_INACT_N1);
        if (pn->pn_va.va_type != VDIR) {
+               /* Always require read access for page cache */
+               mode |= FREAD;
                if (mode & FREAD && p9n->fid_read == P9P_INVALFID) {
                        nfid = NEXTFID(p9p);
                        error = proto_cc_open(pu, p9n->fid_base, nfid,