Patch "NFSv4.1: Fix Oopsable condition in server callback races" has been added to the 4.7-stable tree

[<gregkh@linuxfoundation.org>]

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

    NFSv4.1: Fix Oopsable condition in server callback races

to the 4.7-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:
     nfsv4.1-fix-oopsable-condition-in-server-callback-races.patch
and it can be found in the queue-4.7 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 e09c978aae5bedfdb379be80363b024b7d82638b Mon Sep 17 00:00:00 2001
From: Trond Myklebust <trond.myklebust@primarydata.com>
Date: Sat, 27 Aug 2016 23:44:04 -0400
Subject: NFSv4.1: Fix Oopsable condition in server callback races

From: Trond Myklebust <trond.myklebust@primarydata.com>

commit e09c978aae5bedfdb379be80363b024b7d82638b upstream.

The slot table hasn't been an array since v3.7. Ensure that we
use nfs4_lookup_slot() to access the slot correctly.

Fixes: 87dda67e7386 ("NFSv4.1: Allow SEQUENCE to resize the slot table...")
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/nfs/callback_proc.c |    5 +----
 fs/nfs/nfs4session.c   |   33 +++++++++++++++++++++++++++++++++
 fs/nfs/nfs4session.h   |    1 +
 3 files changed, 35 insertions(+), 4 deletions(-)

--- a/fs/nfs/callback_proc.c
+++ b/fs/nfs/callback_proc.c
@@ -430,11 +430,8 @@ static bool referring_call_exists(struct
 				((u32 *)&rclist->rcl_sessionid.data)[3],
 				ref->rc_sequenceid, ref->rc_slotid);
 
-			spin_lock(&tbl->slot_tbl_lock);
-			status = (test_bit(ref->rc_slotid, tbl->used_slots) &&
-				  tbl->slots[ref->rc_slotid].seq_nr ==
+			status = nfs4_slot_seqid_in_use(tbl, ref->rc_slotid,
 					ref->rc_sequenceid);
-			spin_unlock(&tbl->slot_tbl_lock);
 			if (status)
 				goto out;
 		}
--- a/fs/nfs/nfs4session.c
+++ b/fs/nfs/nfs4session.c
@@ -172,6 +172,39 @@ struct nfs4_slot *nfs4_lookup_slot(struc
 	return ERR_PTR(-E2BIG);
 }
 
+static int nfs4_slot_get_seqid(struct nfs4_slot_table  *tbl, u32 slotid,
+		u32 *seq_nr)
+	__must_hold(&tbl->slot_tbl_lock)
+{
+	struct nfs4_slot *slot;
+
+	slot = nfs4_lookup_slot(tbl, slotid);
+	if (IS_ERR(slot))
+		return PTR_ERR(slot);
+	*seq_nr = slot->seq_nr;
+	return 0;
+}
+
+/*
+ * nfs4_slot_seqid_in_use - test if a slot sequence id is still in use
+ *
+ * Given a slot table, slot id and sequence number, determine if the
+ * RPC call in question is still in flight. This function is mainly
+ * intended for use by the callback channel.
+ */
+bool nfs4_slot_seqid_in_use(struct nfs4_slot_table *tbl, u32 slotid, u32 seq_nr)
+{
+	u32 cur_seq;
+	bool ret = false;
+
+	spin_lock(&tbl->slot_tbl_lock);
+	if (nfs4_slot_get_seqid(tbl, slotid, &cur_seq) == 0 &&
+	    cur_seq == seq_nr && test_bit(slotid, tbl->used_slots))
+		ret = true;
+	spin_unlock(&tbl->slot_tbl_lock);
+	return ret;
+}
+
 /*
  * nfs4_alloc_slot - efficiently look for a free slot
  *
--- a/fs/nfs/nfs4session.h
+++ b/fs/nfs/nfs4session.h
@@ -78,6 +78,7 @@ extern int nfs4_setup_slot_table(struct
 extern void nfs4_shutdown_slot_table(struct nfs4_slot_table *tbl);
 extern struct nfs4_slot *nfs4_alloc_slot(struct nfs4_slot_table *tbl);
 extern struct nfs4_slot *nfs4_lookup_slot(struct nfs4_slot_table *tbl, u32 slotid);
+extern bool nfs4_slot_seqid_in_use(struct nfs4_slot_table  *tbl, u32 slotid, u32 seq_nr);
 extern bool nfs4_try_to_lock_slot(struct nfs4_slot_table *tbl, struct nfs4_slot *slot);
 extern void nfs4_free_slot(struct nfs4_slot_table *tbl, struct nfs4_slot *slot);
 extern void nfs4_slot_tbl_drain_complete(struct nfs4_slot_table *tbl);


Patches currently in stable-queue which might be from trond.myklebust@primarydata.com are

queue-4.7/nfsv4.1-fix-oopsable-condition-in-server-callback-races.patch
queue-4.7/pnfs-ensure-layoutget-and-layoutreturn-are-properly-serialised.patch
queue-4.7/nfsv4.x-fix-a-refcount-leak-in-nfs_callback_up_net.patch
queue-4.7/pnfs-flexfiles-fix-an-oopsable-condition-when-connection-to-the-ds-fails.patch
queue-4.7/nfsv4.1-fix-the-create_session-slot-number-accounting.patch
queue-4.7/pnfs-the-client-must-not-do-i-o-to-the-ds-if-it-s-lease-has-expired.patch