FAILED: patch "[PATCH] svcrdma: Reorder rpcrdma_rn_unregister before rdma_destroy_id" failed to apply to 6.18-stable tree

FAILED: patch "[PATCH] svcrdma: Reorder rpcrdma_rn_unregister before rdma_destroy_id" failed to apply to 6.18-stable tree

[gregkh]

The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 4488e912973773d64368828acf3b8e39d93650ae
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026090308-barstool-liftoff-6f6d@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 4488e912973773d64368828acf3b8e39d93650ae Mon Sep 17 00:00:00 2001
From: Chuck Lever <cel@kernel.org>
Date: Wed, 27 May 2026 11:00:12 -0400
Subject: [PATCH] svcrdma: Reorder rpcrdma_rn_unregister before rdma_destroy_id

svc_rdma_free() caches rdma->sc_cm_id->device before teardown,
then calls rdma_destroy_id(sc_cm_id) which frees the cm_id.
rpcrdma_rn_unregister() follows, but between those two calls
the transport's sc_rn entry is still installed in the device's
rd_xa. A concurrent ib_unregister_device walk can dispatch
svc_rdma_xprt_done() against the now-freed sc_cm_id.

Move rpcrdma_rn_unregister() before rdma_destroy_id() so the
transport's notification entry is removed from the xarray before
the cm_id it references is destroyed.

Also guard the sc_cm_id dereference with a NULL check: the
following patches introduce paths that reach svc_rdma_free()
with sc_cm_id == NULL (listener create failure, ADDR_CHANGE
replacement failure).

Fixes: c4de97f7c454 ("svcrdma: Handle device removal outside of the CM event handler")
Cc: stable@vger.kernel.org
Acked-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20260527-rdma-follow-on-v1-2-1b09bd87b6cd@oracle.com
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
index 9268b6105a74..55e2ca036584 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
@@ -648,10 +648,15 @@ static void svc_rdma_free(struct svc_xprt *xprt)
 {
 	struct svcxprt_rdma *rdma =
 		container_of(xprt, struct svcxprt_rdma, sc_xprt);
-	struct ib_device *device = rdma->sc_cm_id->device;
+	struct ib_device *device;
 
 	might_sleep();
 
+	if (!rdma->sc_cm_id)
+		goto out_free;
+
+	device = rdma->sc_cm_id->device;
+
 	/* This blocks until the Completion Queues are empty */
 	if (rdma->sc_qp && !IS_ERR(rdma->sc_qp))
 		ib_drain_qp(rdma->sc_qp);
@@ -676,11 +681,13 @@ static void svc_rdma_free(struct svc_xprt *xprt)
 	if (rdma->sc_pd && !IS_ERR(rdma->sc_pd))
 		ib_dealloc_pd(rdma->sc_pd);
 
+	if (!test_bit(XPT_LISTENER, &rdma->sc_xprt.xpt_flags))
+		rpcrdma_rn_unregister(device, &rdma->sc_rn);
+
 	/* Destroy the CM ID */
 	rdma_destroy_id(rdma->sc_cm_id);
 
-	if (!test_bit(XPT_LISTENER, &rdma->sc_xprt.xpt_flags))
-		rpcrdma_rn_unregister(device, &rdma->sc_rn);
+out_free:
 	kfree(rdma);
 }
 

[PATCH 6.18.y 1/2] svcrdma: Release transport resources synchronously

[Sasha Levin]

From: Chuck Lever <chuck.lever@oracle.com>

[ Upstream commit bf94dea7fd4e6708d1a784be23db65eff84d82f1 ]

NFSD has always supported added network listeners. The new netlink
protocol now enables the removal of listeners.

Olga noticed that if an RDMA listener is removed and immediately
re-added, the deferred __svc_rdma_free() function might not have
run yet, so some or all of the old listener's RDMA resources
linger, which prevents a new listener on the same address from
being created.

Also, svc_xprt_free() does a module_put() just after calling
->xpo_free(). That means if there is deferred work going on, the
module could be unloaded before that work is even started,
resulting in a UAF.

Neil asks:
> What particular part of __svc_rdma_free() needs to run in order for a
> subsequent registration to succeed?
> Can that bit be run directory from svc_rdma_free() rather than be
> delayed?
> (I know almost nothing about rdma so forgive me if the answers to these
> questions seems obvious)

The reasons I can recall are:

 - Some of the transport tear-down work can sleep
 - Releasing a cm_id is tricky and can deadlock

We might be able to mitigate the second issue with judicious
application of transport reference counting.

Reported-by: Olga Kornievskaia <okorniev@redhat.com>
Closes: https://lore.kernel.org/linux-nfs/20250821204328.89218-1-okorniev@redhat.com/
Suggested-by: NeilBrown <neil@brown.name>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Stable-dep-of: 4488e9129737 ("svcrdma: Reorder rpcrdma_rn_unregister before rdma_destroy_id")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/sunrpc/xprtrdma/svc_rdma_transport.c | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
index c8d994272f6f0..72b653d38bc78 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
@@ -613,12 +613,18 @@ static void svc_rdma_detach(struct svc_xprt *xprt)
 	rdma_disconnect(rdma->sc_cm_id);
 }
 
-static void __svc_rdma_free(struct work_struct *work)
+/**
+ * svc_rdma_free - Release class-specific transport resources
+ * @xprt: Generic svc transport object
+ */
+static void svc_rdma_free(struct svc_xprt *xprt)
 {
 	struct svcxprt_rdma *rdma =
-		container_of(work, struct svcxprt_rdma, sc_work);
+		container_of(xprt, struct svcxprt_rdma, sc_xprt);
 	struct ib_device *device = rdma->sc_cm_id->device;
 
+	might_sleep();
+
 	/* This blocks until the Completion Queues are empty */
 	if (rdma->sc_qp && !IS_ERR(rdma->sc_qp))
 		ib_drain_qp(rdma->sc_qp);
@@ -651,15 +657,6 @@ static void __svc_rdma_free(struct work_struct *work)
 	kfree(rdma);
 }
 
-static void svc_rdma_free(struct svc_xprt *xprt)
-{
-	struct svcxprt_rdma *rdma =
-		container_of(xprt, struct svcxprt_rdma, sc_xprt);
-
-	INIT_WORK(&rdma->sc_work, __svc_rdma_free);
-	schedule_work(&rdma->sc_work);
-}
-
 static int svc_rdma_has_wspace(struct svc_xprt *xprt)
 {
 	struct svcxprt_rdma *rdma =
-- 
2.53.0

[PATCH 6.18.y 2/2] svcrdma: Reorder rpcrdma_rn_unregister before rdma_destroy_id

[Sasha Levin]

From: Chuck Lever <chuck.lever@oracle.com>

[ Upstream commit 4488e912973773d64368828acf3b8e39d93650ae ]

svc_rdma_free() caches rdma->sc_cm_id->device before teardown,
then calls rdma_destroy_id(sc_cm_id) which frees the cm_id.
rpcrdma_rn_unregister() follows, but between those two calls
the transport's sc_rn entry is still installed in the device's
rd_xa. A concurrent ib_unregister_device walk can dispatch
svc_rdma_xprt_done() against the now-freed sc_cm_id.

Move rpcrdma_rn_unregister() before rdma_destroy_id() so the
transport's notification entry is removed from the xarray before
the cm_id it references is destroyed.

Also guard the sc_cm_id dereference with a NULL check: the
following patches introduce paths that reach svc_rdma_free()
with sc_cm_id == NULL (listener create failure, ADDR_CHANGE
replacement failure).

Fixes: c4de97f7c454 ("svcrdma: Handle device removal outside of the CM event handler")
Cc: stable@vger.kernel.org
Acked-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20260527-rdma-follow-on-v1-2-1b09bd87b6cd@oracle.com
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/sunrpc/xprtrdma/svc_rdma_transport.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
index 72b653d38bc78..55f810a22c6aa 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
@@ -621,10 +621,15 @@ static void svc_rdma_free(struct svc_xprt *xprt)
 {
 	struct svcxprt_rdma *rdma =
 		container_of(xprt, struct svcxprt_rdma, sc_xprt);
-	struct ib_device *device = rdma->sc_cm_id->device;
+	struct ib_device *device;
 
 	might_sleep();
 
+	if (!rdma->sc_cm_id)
+		goto out_free;
+
+	device = rdma->sc_cm_id->device;
+
 	/* This blocks until the Completion Queues are empty */
 	if (rdma->sc_qp && !IS_ERR(rdma->sc_qp))
 		ib_drain_qp(rdma->sc_qp);
@@ -649,11 +654,13 @@ static void svc_rdma_free(struct svc_xprt *xprt)
 	if (rdma->sc_pd && !IS_ERR(rdma->sc_pd))
 		ib_dealloc_pd(rdma->sc_pd);
 
+	if (!test_bit(XPT_LISTENER, &rdma->sc_xprt.xpt_flags))
+		rpcrdma_rn_unregister(device, &rdma->sc_rn);
+
 	/* Destroy the CM ID */
 	rdma_destroy_id(rdma->sc_cm_id);
 
-	if (!test_bit(XPT_LISTENER, &rdma->sc_xprt.xpt_flags))
-		rpcrdma_rn_unregister(device, &rdma->sc_rn);
+out_free:
 	kfree(rdma);
 }
 
-- 
2.53.0