Patch "nfsd: ensure that the ol stateid hash reference is only put once" has been added to the 4.2-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    nfsd: ensure that the ol stateid hash reference is only put once

to the 4.2-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     nfsd-ensure-that-the-ol-stateid-hash-reference-is-only-put-once.patch
and it can be found in the queue-4.2 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From e85687393f3ee0a77ccca016f903d1558bb69258 Mon Sep 17 00:00:00 2001
From: Jeff Layton <jlayton@poochiereds.net>
Date: Mon, 24 Aug 2015 12:41:47 -0400
Subject: nfsd: ensure that the ol stateid hash reference is only put once

From: Jeff Layton <jlayton@poochiereds.net>

commit e85687393f3ee0a77ccca016f903d1558bb69258 upstream.

When an open or lock stateid is hashed, we take an extra reference to
it. When we unhash it, we drop that reference. The code however does
not properly account for the case where we have two callers concurrently
trying to unhash the stateid. This can lead to list corruption and the
hash reference being put more than once.

Fix this by having unhash_ol_stateid use list_del_init on the st_perfile
list_head, and then testing to see if that list_head is empty before
releasing the hash reference. This means that some of the unhashing
wrappers now become bool return functions so we can test to see whether
the stateid was unhashed before we put the reference.

Reported-by: Andrew W Elble <aweits@rit.edu>
Tested-by: Andrew W Elble <aweits@rit.edu>
Reported-by: Anna Schumaker <Anna.Schumaker@netapp.com>
Tested-by: Anna Schumaker <Anna.Schumaker@netapp.com>
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/nfsd/nfs4state.c |   58 ++++++++++++++++++++++++++++++++--------------------
 1 file changed, 36 insertions(+), 22 deletions(-)

--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -1004,16 +1004,20 @@ static void nfs4_put_stateowner(struct n
 	sop->so_ops->so_free(sop);
 }
 
-static void unhash_ol_stateid(struct nfs4_ol_stateid *stp)
+static bool unhash_ol_stateid(struct nfs4_ol_stateid *stp)
 {
 	struct nfs4_file *fp = stp->st_stid.sc_file;
 
 	lockdep_assert_held(&stp->st_stateowner->so_client->cl_lock);
 
+	if (list_empty(&stp->st_perfile))
+		return false;
+
 	spin_lock(&fp->fi_lock);
-	list_del(&stp->st_perfile);
+	list_del_init(&stp->st_perfile);
 	spin_unlock(&fp->fi_lock);
 	list_del(&stp->st_perstateowner);
+	return true;
 }
 
 static void nfs4_free_ol_stateid(struct nfs4_stid *stid)
@@ -1063,25 +1067,27 @@ static void put_ol_stateid_locked(struct
 	list_add(&stp->st_locks, reaplist);
 }
 
-static void unhash_lock_stateid(struct nfs4_ol_stateid *stp)
+static bool unhash_lock_stateid(struct nfs4_ol_stateid *stp)
 {
 	struct nfs4_openowner *oo = openowner(stp->st_openstp->st_stateowner);
 
 	lockdep_assert_held(&oo->oo_owner.so_client->cl_lock);
 
 	list_del_init(&stp->st_locks);
-	unhash_ol_stateid(stp);
 	nfs4_unhash_stid(&stp->st_stid);
+	return unhash_ol_stateid(stp);
 }
 
 static void release_lock_stateid(struct nfs4_ol_stateid *stp)
 {
 	struct nfs4_openowner *oo = openowner(stp->st_openstp->st_stateowner);
+	bool unhashed;
 
 	spin_lock(&oo->oo_owner.so_client->cl_lock);
-	unhash_lock_stateid(stp);
+	unhashed = unhash_lock_stateid(stp);
 	spin_unlock(&oo->oo_owner.so_client->cl_lock);
-	nfs4_put_stid(&stp->st_stid);
+	if (unhashed)
+		nfs4_put_stid(&stp->st_stid);
 }
 
 static void unhash_lockowner_locked(struct nfs4_lockowner *lo)
@@ -1129,7 +1135,7 @@ static void release_lockowner(struct nfs
 	while (!list_empty(&lo->lo_owner.so_stateids)) {
 		stp = list_first_entry(&lo->lo_owner.so_stateids,
 				struct nfs4_ol_stateid, st_perstateowner);
-		unhash_lock_stateid(stp);
+		WARN_ON(!unhash_lock_stateid(stp));
 		put_ol_stateid_locked(stp, &reaplist);
 	}
 	spin_unlock(&clp->cl_lock);
@@ -1142,21 +1148,26 @@ static void release_open_stateid_locks(s
 {
 	struct nfs4_ol_stateid *stp;
 
+	lockdep_assert_held(&open_stp->st_stid.sc_client->cl_lock);
+
 	while (!list_empty(&open_stp->st_locks)) {
 		stp = list_entry(open_stp->st_locks.next,
 				struct nfs4_ol_stateid, st_locks);
-		unhash_lock_stateid(stp);
+		WARN_ON(!unhash_lock_stateid(stp));
 		put_ol_stateid_locked(stp, reaplist);
 	}
 }
 
-static void unhash_open_stateid(struct nfs4_ol_stateid *stp,
+static bool unhash_open_stateid(struct nfs4_ol_stateid *stp,
 				struct list_head *reaplist)
 {
+	bool unhashed;
+
 	lockdep_assert_held(&stp->st_stid.sc_client->cl_lock);
 
-	unhash_ol_stateid(stp);
+	unhashed = unhash_ol_stateid(stp);
 	release_open_stateid_locks(stp, reaplist);
+	return unhashed;
 }
 
 static void release_open_stateid(struct nfs4_ol_stateid *stp)
@@ -1164,8 +1175,8 @@ static void release_open_stateid(struct
 	LIST_HEAD(reaplist);
 
 	spin_lock(&stp->st_stid.sc_client->cl_lock);
-	unhash_open_stateid(stp, &reaplist);
-	put_ol_stateid_locked(stp, &reaplist);
+	if (unhash_open_stateid(stp, &reaplist))
+		put_ol_stateid_locked(stp, &reaplist);
 	spin_unlock(&stp->st_stid.sc_client->cl_lock);
 	free_ol_stateid_reaplist(&reaplist);
 }
@@ -1210,8 +1221,8 @@ static void release_openowner(struct nfs
 	while (!list_empty(&oo->oo_owner.so_stateids)) {
 		stp = list_first_entry(&oo->oo_owner.so_stateids,
 				struct nfs4_ol_stateid, st_perstateowner);
-		unhash_open_stateid(stp, &reaplist);
-		put_ol_stateid_locked(stp, &reaplist);
+		if (unhash_open_stateid(stp, &reaplist))
+			put_ol_stateid_locked(stp, &reaplist);
 	}
 	spin_unlock(&clp->cl_lock);
 	free_ol_stateid_reaplist(&reaplist);
@@ -4751,7 +4762,7 @@ nfsd4_free_stateid(struct svc_rqst *rqst
 		if (check_for_locks(stp->st_stid.sc_file,
 				    lockowner(stp->st_stateowner)))
 			break;
-		unhash_lock_stateid(stp);
+		WARN_ON(!unhash_lock_stateid(stp));
 		spin_unlock(&cl->cl_lock);
 		nfs4_put_stid(s);
 		ret = nfs_ok;
@@ -4967,20 +4978,23 @@ out:
 static void nfsd4_close_open_stateid(struct nfs4_ol_stateid *s)
 {
 	struct nfs4_client *clp = s->st_stid.sc_client;
+	bool unhashed;
 	LIST_HEAD(reaplist);
 
 	s->st_stid.sc_type = NFS4_CLOSED_STID;
 	spin_lock(&clp->cl_lock);
-	unhash_open_stateid(s, &reaplist);
+	unhashed = unhash_open_stateid(s, &reaplist);
 
 	if (clp->cl_minorversion) {
-		put_ol_stateid_locked(s, &reaplist);
+		if (unhashed)
+			put_ol_stateid_locked(s, &reaplist);
 		spin_unlock(&clp->cl_lock);
 		free_ol_stateid_reaplist(&reaplist);
 	} else {
 		spin_unlock(&clp->cl_lock);
 		free_ol_stateid_reaplist(&reaplist);
-		move_to_close_lru(s, clp->net);
+		if (unhashed)
+			move_to_close_lru(s, clp->net);
 	}
 }
 
@@ -6019,7 +6033,7 @@ nfsd_inject_add_lock_to_list(struct nfs4
 
 static u64 nfsd_foreach_client_lock(struct nfs4_client *clp, u64 max,
 				    struct list_head *collect,
-				    void (*func)(struct nfs4_ol_stateid *))
+				    bool (*func)(struct nfs4_ol_stateid *))
 {
 	struct nfs4_openowner *oop;
 	struct nfs4_ol_stateid *stp, *st_next;
@@ -6033,9 +6047,9 @@ static u64 nfsd_foreach_client_lock(stru
 			list_for_each_entry_safe(lst, lst_next,
 					&stp->st_locks, st_locks) {
 				if (func) {
-					func(lst);
-					nfsd_inject_add_lock_to_list(lst,
-								collect);
+					if (func(lst))
+						nfsd_inject_add_lock_to_list(lst,
+									collect);
 				}
 				++count;
 				/*


Patches currently in stable-queue which might be from jlayton@poochiereds.net are

queue-4.2/nfsd-ensure-that-delegation-stateid-hash-references-are-only-put-once.patch
queue-4.2/nfsd-ensure-that-the-ol-stateid-hash-reference-is-only-put-once.patch