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>

diff --git a/fs/nfs/dns_resolve.c b/fs/nfs/dns_resolve.c
index 31c26c4dcc238110de0fa7374f1a2ab51a1541cd..ca4b11ec87a292e92e5d9496f8ac194d97a5bf9f 100644 (file)
--- 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();