FAILED: patch "[PATCH] NFSD: Complete a cld upcall when the daemon closes the pipe" failed to apply to 6.12-stable tree

The patch below does not apply to the 6.12-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 <[email protected]>.

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-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 2a83fcb50f3c25c493cc4389619340fefe9d6ac4
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026110453-devotee-unsuited-ab14@gregkh' --subject-prefix 'PATCH 6.12.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

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

From 2a83fcb50f3c25c493cc4389619340fefe9d6ac4 Mon Sep 17 00:00:00 2001
From: Chuck Lever <[email protected]>
Date: Tue, 1 Sep 2026 16:19:47 -0400
Subject: [PATCH] NFSD: Complete a cld upcall when the daemon closes the pipe

Once nfsdcld has read a whole upcall, rpc_pipe_read() unlinks the message from every pipe list, so the purges in rpc_pipe_release() and rpc_close_pipes() no longer reach it. cld_upcall_ops supplies no .release_pipe callback, and cld_pipe_destroy_msg() returns without completing the upcall because a downcall is expected to follow. A daemon that exits between the read and the write therefore strands its waiter: the nfsd thread sleeps in TASK_UNINTERRUPTIBLE in __cld_pipe_upcall() and never returns, hung task warnings follow, and the server cannot be shut down.

Add a .release_pipe that completes every upcall the daemon has consumed. cu_inflight distinguishes those from upcalls still queued on the pipe, which the framework purges before it calls this callback; cld_pipe_downcall() removes an upcall it accepts from cn_list under the same lock. Neither can be completed twice.

Fail the stranded upcall with -EPIPE rather than the -EAGAIN that makes cld_pipe_upcall() retry. The daemon consumed the request, so whether it acted on it before exiting is unknown.

index 1a9ea6393740..5e7788e3fb79 100644
@@ -871,10 +871,34 @@ cld_pipe_destroy_msg(struct rpc_pipe_msg *msg)
 	complete(&cup->cu_done);
 }
 
+/*
+ * An upcall the daemon has consumed is off every pipe list, so the
+ * purge in rpc_pipe_release() and rpc_close_pipes() cannot reach it.
+ * Release its waiter here instead; no downcall can arrive now.
+ */
+static void
+cld_release_pipe(struct inode *inode)
+{
+	struct nfsd_net *nn = net_generic(inode->i_sb->s_fs_info, nfsd_net_id);
+	struct cld_net *cn = nn->cld_net;
+	struct cld_upcall *cup;
+
+	spin_lock(&cn->cn_lock);
+	list_for_each_entry(cup, &cn->cn_list, cu_list) {
+		if (!cup->cu_inflight)
+			continue;
+		cup->cu_inflight = false;
+		cup->cu_pipe_msg.errno = -EPIPE;
+		complete(&cup->cu_done);
+	}
+	spin_unlock(&cn->cn_lock);
+}
+
 static const struct rpc_pipe_ops cld_upcall_ops = {
 	.upcall		= rpc_pipe_generic_upcall,
 	.downcall	= cld_pipe_downcall,
 	.destroy_msg	= cld_pipe_destroy_msg,
+	.release_pipe	= cld_release_pipe,
 };
 
 static int

From: Chuck Lever <[email protected]>

[ Upstream commit c559b05610557fa3c6c30259261f6dae523b3f23 ]

__cld_pipe_upcall() builds its struct rpc_pipe_msg on the stack and hands it to rpc_queue_upcall(), which links it into a list the pipe owns until the message is released. Only the completion rules keep that frame alive for as long as the pipe refers to it, and the peer that drives those rules is an untrusted userspace daemon. The gss and idmap upcalls do not take that on: each keeps the message in the object it already allocates.

Do the same here and put the message in struct cld_upcall, beside the reply buffer it carries. cld_pipe_destroy_msg() then reaches the upcall from the message directly rather than through msg->data.

Stable-dep-of: 2a83fcb50f3c ("NFSD: Complete a cld upcall when the daemon closes the pipe")

---
 fs/nfsd/nfs4recover.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

index 104dafbe881bc..b493bb059a8b0 100644
@@ -730,6 +730,7 @@ struct cld_upcall {
 	struct completion	 cu_done;
 	/* daemon has read the whole upcall; protected by cn_lock */
 	bool			 cu_inflight;
+	struct rpc_pipe_msg	 cu_pipe_msg;
 	union {
 		struct cld_msg_hdr	 cu_hdr;
 		struct cld_msg		 cu_msg;

@@ -741,22 +742,22 @@ static int
 __cld_pipe_upcall(struct rpc_pipe *pipe, void *cmsg, struct nfsd_net *nn)
 {
 	int ret;
-	struct rpc_pipe_msg msg;
 	struct cld_upcall *cup = container_of(cmsg, struct cld_upcall, cu_u);
+	struct rpc_pipe_msg *msg = &cup->cu_pipe_msg;
 
-	memset(&msg, 0, sizeof(msg));
-	msg.data = cmsg;
-	msg.len = nn->client_tracking_ops->msglen;
+	memset(msg, 0, sizeof(*msg));
+	msg->data = cmsg;
+	msg->len = nn->client_tracking_ops->msglen;
 
-	ret = rpc_queue_upcall(pipe, &msg);
+	ret = rpc_queue_upcall(pipe, msg);
 	if (ret < 0) {
 		goto out;
 	}
 
 	wait_for_completion(&cup->cu_done);
 
-	if (msg.errno < 0)
-		ret = msg.errno;
+	if (msg->errno < 0)
+		ret = msg->errno;
 out:
 	return ret;
 }

@@ -929,9 +930,8 @@ cld_pipe_downcall(struct file *filp, const char __user *src, size_t mlen)
 static void
 cld_pipe_destroy_msg(struct rpc_pipe_msg *msg)
 {
-	struct cld_msg *cmsg = msg->data;
-	struct cld_upcall *cup = container_of(cmsg, struct cld_upcall,
-						 cu_u.cu_msg);
+	struct cld_upcall *cup = container_of(msg, struct cld_upcall,
+						 cu_pipe_msg);
 	struct cld_net *cn = cup->cu_net;
 
 	/*

2.53.0

From: Chuck Lever <[email protected]>

[ Upstream commit 2a83fcb50f3c25c493cc4389619340fefe9d6ac4 ]

Once nfsdcld has read a whole upcall, rpc_pipe_read() unlinks the message from every pipe list, so the purges in rpc_pipe_release() and rpc_close_pipes() no longer reach it. cld_upcall_ops supplies no .release_pipe callback, and cld_pipe_destroy_msg() returns without completing the upcall because a downcall is expected to follow. A daemon that exits between the read and the write therefore strands its waiter: the nfsd thread sleeps in TASK_UNINTERRUPTIBLE in __cld_pipe_upcall() and never returns, hung task warnings follow, and the server cannot be shut down.

Add a .release_pipe that completes every upcall the daemon has consumed. cu_inflight distinguishes those from upcalls still queued on the pipe, which the framework purges before it calls this callback; cld_pipe_downcall() removes an upcall it accepts from cn_list under the same lock. Neither can be completed twice.

Fail the stranded upcall with -EPIPE rather than the -EAGAIN that makes cld_pipe_upcall() retry. The daemon consumed the request, so whether it acted on it before exiting is unknown.

---
 fs/nfsd/nfs4recover.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

index b493bb059a8b0..9c7f6d90a1b99 100644
@@ -948,10 +948,34 @@ cld_pipe_destroy_msg(struct rpc_pipe_msg *msg)
 	complete(&cup->cu_done);
 }
 
+/*
+ * An upcall the daemon has consumed is off every pipe list, so the
+ * purge in rpc_pipe_release() and rpc_close_pipes() cannot reach it.
+ * Release its waiter here instead; no downcall can arrive now.
+ */
+static void
+cld_release_pipe(struct inode *inode)
+{
+	struct nfsd_net *nn = net_generic(inode->i_sb->s_fs_info, nfsd_net_id);
+	struct cld_net *cn = nn->cld_net;
+	struct cld_upcall *cup;
+
+	spin_lock(&cn->cn_lock);
+	list_for_each_entry(cup, &cn->cn_list, cu_list) {
+		if (!cup->cu_inflight)
+			continue;
+		cup->cu_inflight = false;
+		cup->cu_pipe_msg.errno = -EPIPE;
+		complete(&cup->cu_done);
+	}
+	spin_unlock(&cn->cn_lock);
+}
+
 static const struct rpc_pipe_ops cld_upcall_ops = {
 	.upcall		= rpc_pipe_generic_upcall,
 	.downcall	= cld_pipe_downcall,
 	.destroy_msg	= cld_pipe_destroy_msg,
+	.release_pipe	= cld_release_pipe,
 };
 
 static int

2.53.0