[PATCH 037/241] NFS: fix bug in legacy DNS resolver.

Herton Ronaldo Krzesinski herton.krzesinski at canonical.com
Thu Dec 13 13:56:42 UTC 2012 -stable review patch.  If anyone has any objections, please let me know.


From: NeilBrown <neilb at suse.de>

commit 8d96b10639fb402357b75b055b1e82a65ff95050 upstream.

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 at oracle.com>
Tested-by: Chuck Lever <chuck.lever at oracle.com>
Signed-off-by: NeilBrown <neilb at suse.de>
Signed-off-by: Trond Myklebust <Trond.Myklebust at netapp.com>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
 fs/nfs/dns_resolve.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/dns_resolve.c b/fs/nfs/dns_resolve.c
index b3924b8..786cd65 100644
--- a/fs/nfs/dns_resolve.c
+++ b/fs/nfs/dns_resolve.c
@@ -214,7 +214,7 @@ static int nfs_dns_parse(struct cache_detail *cd, char *buf, int buflen)
 	struct nfs_dns_ent key, *item;
-	unsigned long ttl;
+	unsigned int ttl;
 	ssize_t len;
 	int ret = -EINVAL;
@@ -237,7 +237,8 @@ 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();

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