Commit 8d96b106 authored Oct 31, 2012 by NeilBrown Committed by Trond Myklebust Oct 31, 2012

NFS: fix bug in legacy DNS resolver.



The DNS resolver's use of the sunrpc cache involves a 'ttl' number
(relative) rather that a timeout (absolute).  This confused me when
I wrote
  commit c5b29f88
     "sunrpc: use seconds since boot in expiry cache"

and I managed to break it.  The effect is that any TTL is interpreted
as 0, and nothing useful gets into the cache.

This patch removes the use of get_expiry() - which really expects an
expiry time - and uses get_uint() instead, treating the int correctly
as a ttl.

This fixes a regression that has been present since 2.6.37, causing
certain NFS accesses in certain environments to incorrectly fail.

Reported-by: Chuck Lever <chuck.lever@oracle.com>
Tested-by: Chuck Lever <chuck.lever@oracle.com>
Cc: stable@vger.kernel.org
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

parent 2b1bc308

fs/nfs/dns_resolve.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -217,7 +217,7 @@ static int nfs_dns_parse(struct cache_detail cd, char buf, int buflen)
		{
		char buf1[NFS_DNS_HOSTNAME_MAXLEN+1];
		struct nfs_dns_ent key, *item;
		unsigned long ttl;
		unsigned int ttl;
		ssize_t len;
		int ret = -EINVAL;

		@@ -240,7 +240,8 @@ static int nfs_dns_parse(struct cache_detail cd, char buf, int buflen)
		key.namelen = len;
		memset(&key.h, 0, sizeof(key.h));

		ttl = get_expiry(&buf);
		if (get_uint(&buf, &ttl) < 0)
		goto out;
		if (ttl == 0)
		goto out;
		key.h.expiry_time = ttl + seconds_since_boot();