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 c5b29f885afe890f953f7f23424045cdad31d3e4
     "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>

1 files changed, 3 insertions, 2 deletions

diff --git a/fs/nfs/dns_resolve.c b/fs/nfs/dns_resolve.c
index 31c26c4dcc23..ca4b11ec87a2 100644
--- a/fs/nfs/dns_resolve.c
+++ b/fs/nfs/dns_resolve.c
@@ -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();