[NFS] [PATCH] knfsd : export : Fix bug of svc_export_parse()

[Neil Brown]

On Tuesday March 27, yjwei at cn.fujitsu.com wrote:
> Nobody replied yet, but I think this is really a BUG of exportfs.
> exportfs command does not check so strictly, so maybe some unreasonable
> fh.key can be add to /proc/net/rpc/nfsd.fh/channel, but used this key to
> find fh.handle, this always be fail and still retry.
> 
> It's this correct?

Sorry for not replying earlier.

Yes, you have identified a real problem, but I'm not sure I agree with
the first.

If someone (mountd) tried to tell the kernel to export "/dev/null", it
fails with an error (-ENODIR), and I think this is correct.

Mountd should respond properly to this error, which it doesn't at the
moment.
When the request comes via the MOUNT protocol from an NFSv2 or NFSv3
client, mountd will fail the mount as it should.
However when the request comes from the kernel due to an NFSv4
request, the error is just ignored.  In that case we really should be
telling the kernel that the filehandle is not valid by writing out an
appropriate message.


Maybe something like this in nfs-utils.
What do you think?

Signed-off-by: Neil Brown <neilb at suse.de>

### Diffstat output
 ./utils/mountd/cache.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff .prev/utils/mountd/cache.c ./utils/mountd/cache.c
--- .prev/utils/mountd/cache.c	2007-03-27 12:11:52.000000000 +1000
+++ ./utils/mountd/cache.c	2007-03-27 12:13:40.000000000 +1000
@@ -469,7 +469,8 @@ void nfsd_fh(FILE *f)
 	}
 
 	if (found)
-		cache_export_ent(dom, found, found_path);
+		if (cache_export_ent(dom, found, found_path) < 0)
+			found = 0;
 
 	qword_print(f, dom);
 	qword_printint(f, fsidtype);
@@ -619,8 +620,10 @@ void nfsd_export(FILE *f)
 	}
 
 	if (found) {
-		dump_to_cache(f, dom, path, &found->m_export);
-		mountlist_add(dom, path);
+		if (dump_to_cache(f, dom, path, &found->m_export) < 0)
+			dump_to_cache(f, dom, path, NULL);
+		else
+			mountlist_add(dom, path);
 	} else {
 		dump_to_cache(f, dom, path, NULL);
 	}