[PATCH 001 of 2] knfsd: Use a spinlock to protect sk_info_authunix

NeilBrown
2007-04-17T02:02:00Z

sk_info_authunix is not being protected properly so the object that
it points to can be cache_put twice, leading to corruption.

We borrow svsk->sk_defer_lock to provide the protection. We should probably
rename that lock to have a more generic name - later.

Thanks to Gabriel for reporting this.

Cc: Greg Banks <gnb@melbourne.sgi.com>
Cc: Gabriel Barazer <gabriel@oxeva.fr>
Signed-off-by: Neil Brown <neilb@suse.de>

### Diffstat output
./net/sunrpc/svcauth_unix.c | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)

diff .prev/net/sunrpc/svcauth_unix.c ./net/sunrpc/svcauth_unix.c
--- .prev/net/sunrpc/svcauth_unix.c 2007-04-17 11:42:14.000000000 +1000
+++ ./net/sunrpc/svcauth_unix.c 2007-04-17 11:42:21.000000000 +1000
@@ -383,7 +383,10 @@ void svcauth_unix_purge(void)
static inline struct ip_map *
ip_map_cached_get(struct svc_rqst *rqstp)
{
- struct ip_map *ipm = rqstp->rq_sock->sk_info_authunix;
+ struct ip_map *ipm;
+ struct svc_sock *svsk = rqstp->rq_sock;
+ spin_lock_bh(&svsk->sk_defer_lock);
+ ipm = svsk->sk_info_authunix;
if (ipm != NULL) {
if (!cache_valid(&ipm->h)) {
/*
@@ -391,12 +394,14 @@ ip_map_cached_get(struct svc_rqst *rqstp
* remembered, e.g. by a second mount from the
* same IP address.
*/
- rqstp->rq_sock->sk_info_authunix = NULL;
+ svsk->sk_info_authunix = NULL;
+ spin_unlock_bh(&svsk->sk_defer_lock);
cache_put(&ipm->h, &ip_map_cache);
return NULL;
}
cache_get(&ipm->h);
}
+ spin_unlock_bh(&svsk->sk_defer_lock);
return ipm;
}

@@ -405,9 +410,15 @@ ip_map_cached_put(struct svc_rqst *rqstp
{
struct svc_sock *svsk = rqstp->rq_sock;

- if (svsk->sk_sock->type == SOCK_STREAM && svsk->sk_info_authunix == NULL)
- svsk->sk_info_authunix = ipm; /* newly cached, keep the reference */
- else
+ spin_lock_bh(&svsk->sk_defer_lock);
+ if (svsk->sk_sock->type == SOCK_STREAM &&
+ svsk->sk_info_authunix == NULL) {
+ /* newly cached, keep the reference */
+ svsk->sk_info_authunix = ipm;
+ ipm = NULL;
+ }
+ spin_unlock_bh(&svsk->sk_defer_lock);
+ if (ipm)
cache_put(&ipm->h, &ip_map_cache);
}