This is a note to let you know that I've just added the patch titled
NFS: Fix an LOCK/OPEN race when unlinking an open file
to the 4.4-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:
nfs-fix-an-lock-open-race-when-unlinking-an-open-file.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 11476e9dec39d90fe1e9bf12abc6f3efe35a073d Mon Sep 17 00:00:00 2001
From: Chuck Lever <chuck.lever@xxxxxxxxxx>
Date: Mon, 11 Apr 2016 16:20:22 -0400
Subject: NFS: Fix an LOCK/OPEN race when unlinking an open file
From: Chuck Lever <chuck.lever@xxxxxxxxxx>
commit 11476e9dec39d90fe1e9bf12abc6f3efe35a073d upstream.
At Connectathon 2016, we found that recent upstream Linux clients
would occasionally send a LOCK operation with a zero stateid. This
appeared to happen in close proximity to another thread returning
a delegation before unlinking the same file while it remained open.
Earlier, the client received a write delegation on this file and
returned the open stateid. Now, as it is getting ready to unlink the
file, it returns the write delegation. But there is still an open
file descriptor on that file, so the client must OPEN the file
again before it returns the delegation.
Since commit 24311f884189 ('NFSv4: Recovery of recalled read
delegations is broken'), nfs_open_delegation_recall() clears the
NFS_DELEGATED_STATE flag _before_ it sends the OPEN. This allows a
racing LOCK on the same inode to be put on the wire before the OPEN
operation has returned a valid open stateid.
To eliminate this race, serialize delegation return with the
acquisition of a file lock on the same file. Adopt the same approach
as is used in the unlock path.
This patch also eliminates a similar race seen when sending a LOCK
operation at the same time as returning a delegation on the same file.
Fixes: 24311f884189 ('NFSv4: Recovery of recalled read ... ')
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
[Anna: Add sentence about LOCK / delegation race]
Signed-off-by: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/nfs/nfs4proc.c | 4 ++++
1 file changed, 4 insertions(+)
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -6054,6 +6054,7 @@ static int nfs41_lock_expired(struct nfs
static int _nfs4_proc_setlk(struct nfs4_state *state, int cmd, struct file_lock *request)
{
struct nfs_inode *nfsi = NFS_I(state->inode);
+ struct nfs4_state_owner *sp = state->owner;
unsigned char fl_flags = request->fl_flags;
int status = -ENOLCK;
@@ -6068,6 +6069,7 @@ static int _nfs4_proc_setlk(struct nfs4_
status = do_vfs_lock(state->inode, request);
if (status < 0)
goto out;
+ mutex_lock(&sp->so_delegreturn_mutex);
down_read(&nfsi->rwsem);
if (test_bit(NFS_DELEGATED_STATE, &state->flags)) {
/* Yes: cache locks! */
@@ -6075,9 +6077,11 @@ static int _nfs4_proc_setlk(struct nfs4_
request->fl_flags = fl_flags & ~FL_SLEEP;
status = do_vfs_lock(state->inode, request);
up_read(&nfsi->rwsem);
+ mutex_unlock(&sp->so_delegreturn_mutex);
goto out;
}
up_read(&nfsi->rwsem);
+ mutex_unlock(&sp->so_delegreturn_mutex);
status = _nfs4_do_setlk(state, cmd, request, NFS_LOCK_NEW);
out:
request->fl_flags = fl_flags;
Patches currently in stable-queue which might be from chuck.lever@xxxxxxxxxx are
queue-4.4/nfs-fix-an-lock-open-race-when-unlinking-an-open-file.patch
queue-4.4/xprtrdma-fix-additional-uses-of-spin_lock_irqsave-rb_lock.patch
queue-4.4/xprtrdma-xprt_rdma_free-must-not-release-backchannel-reqs.patch
queue-4.4/xprtrdma-rpcrdma_bc_receive_call-should-init-rq_private_buf.len.patch
