[PATCH 4.4 032/146] nfsd: Extend the mutex holding region around in nfsd4_process_open2()

Greg Kroah-Hartman
2016-07-25T21:02:37Z

From: Oleg Drokin <green@linuxhacker.ru>

commit 5cc1fb2a093e254b656c64ff24b0b76bed1d34d9 upstream.

To avoid racing entry into nfs4_get_vfs_file().
Make init_open_stateid() return with locked stateid to be unlocked
by the caller.

Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/nfsd/nfs4state.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)

--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -3452,6 +3452,10 @@ init_open_stateid(struct nfs4_ol_stateid
struct nfs4_openowner *oo = open->op_openowner;
struct nfs4_ol_stateid *retstp = NULL;

+ /* We are moving these outside of the spinlocks to avoid the warnings */
+ mutex_init(&stp->st_mutex);
+ mutex_lock(&stp->st_mutex);
+
spin_lock(&oo->oo_owner.so_client->cl_lock);
spin_lock(&fp->fi_lock);

@@ -3467,13 +3471,17 @@ init_open_stateid(struct nfs4_ol_stateid
stp->st_access_bmap = 0;
stp->st_deny_bmap = 0;
stp->st_openstp = NULL;
- mutex_init(&stp->st_mutex);
list_add(&stp->st_perstateowner, &oo->oo_owner.so_stateids);
list_add(&stp->st_perfile, &fp->fi_stateids);

out_unlock:
spin_unlock(&fp->fi_lock);
spin_unlock(&oo->oo_owner.so_client->cl_lock);
+ if (retstp) {
+ mutex_lock(&retstp->st_mutex);
+ /* Not that we need to, just for neatness */
+ mutex_unlock(&stp->st_mutex);
+ }
return retstp;
}

@@ -4309,11 +4317,14 @@ nfsd4_process_open2(struct svc_rqst *rqs
} else {
stp = open->op_stp;
open->op_stp = NULL;
+ /*
+ * init_open_stateid() either returns a locked stateid
+ * it found, or initializes and locks the new one we passed in
+ */
swapstp = init_open_stateid(stp, fp, open);
if (swapstp) {
nfs4_put_stid(&stp->st_stid);
stp = swapstp;
- mutex_lock(&stp->st_mutex);
status = nfs4_upgrade_open(rqstp, fp, current_fh,
stp, open);
if (status) {
@@ -4322,7 +4333,6 @@ nfsd4_process_open2(struct svc_rqst *rqs
}
goto upgrade_out;
}
- mutex_lock(&stp->st_mutex);
status = nfs4_get_vfs_file(rqstp, fp, current_fh, stp, open);
if (status) {
mutex_unlock(&stp->st_mutex);