FAILED: patch "[PATCH] rxrpc: Fix call removal to use RCU safe deletion" failed to apply to 5.15-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 5.15-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-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 146d4ab94cf129ee06cd467cb5c71368a6b5bad6
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026041333-uncoated-appendix-fea5@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

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

From 146d4ab94cf129ee06cd467cb5c71368a6b5bad6 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Wed, 8 Apr 2026 13:12:32 +0100
Subject: [PATCH] rxrpc: Fix call removal to use RCU safe deletion

Fix rxrpc call removal from the rxnet->calls list to use list_del_rcu()
rather than list_del_init() to prevent stuffing up reading
/proc/net/rxrpc/calls from potentially getting into an infinite loop.

This, however, means that list_empty() no longer works on an entry that's
been deleted from the list, making it harder to detect prior deletion.  Fix
this by:

Firstly, make rxrpc_destroy_all_calls() only dump the first ten calls that
are unexpectedly still on the list.  Limiting the number of steps means
there's no need to call cond_resched() or to remove calls from the list
here, thereby eliminating the need for rxrpc_put_call() to check for that.

rxrpc_put_call() can then be fixed to unconditionally delete the call from
the list as it is the only place that the deletion occurs.

Fixes: 2baec2c3f854 ("rxrpc: Support network namespacing")
Closes: https://sashiko.dev/#/patchset/20260319150150.4189381-1-dhowells%40redhat.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: Jeffrey Altman <jaltman@auristor.com>
cc: Linus Torvalds <torvalds@linux-foundation.org>
cc: Simon Horman <horms@kernel.org>
cc: linux-afs@lists.infradead.org
cc: stable@kernel.org
Link: https://patch.msgid.link/20260408121252.2249051-5-dhowells@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/trace/events/rxrpc.h b/include/trace/events/rxrpc.h
index 869f97c9bf73..a826cd80007b 100644
--- a/include/trace/events/rxrpc.h
+++ b/include/trace/events/rxrpc.h
@@ -347,7 +347,7 @@
 	EM(rxrpc_call_see_release,		"SEE release ") \
 	EM(rxrpc_call_see_userid_exists,	"SEE u-exists") \
 	EM(rxrpc_call_see_waiting_call,		"SEE q-conn  ") \
-	E_(rxrpc_call_see_zap,			"SEE zap     ")
+	E_(rxrpc_call_see_still_live,		"SEE !still-l")
 
 #define rxrpc_txqueue_traces \
 	EM(rxrpc_txqueue_await_reply,		"AWR") \
diff --git a/net/rxrpc/call_object.c b/net/rxrpc/call_object.c
index 918f41d97a2f..59329cfe1532 100644
--- a/net/rxrpc/call_object.c
+++ b/net/rxrpc/call_object.c
@@ -654,11 +654,9 @@ void rxrpc_put_call(struct rxrpc_call *call, enum rxrpc_call_trace why)
 	if (dead) {
 		ASSERTCMP(__rxrpc_call_state(call), ==, RXRPC_CALL_COMPLETE);
 
-		if (!list_empty(&call->link)) {
-			spin_lock(&rxnet->call_lock);
-			list_del_init(&call->link);
-			spin_unlock(&rxnet->call_lock);
-		}
+		spin_lock(&rxnet->call_lock);
+		list_del_rcu(&call->link);
+		spin_unlock(&rxnet->call_lock);
 
 		rxrpc_cleanup_call(call);
 	}
@@ -730,24 +728,20 @@ void rxrpc_destroy_all_calls(struct rxrpc_net *rxnet)
 	_enter("");
 
 	if (!list_empty(&rxnet->calls)) {
+		int shown = 0;
+
 		spin_lock(&rxnet->call_lock);
 
-		while (!list_empty(&rxnet->calls)) {
-			call = list_entry(rxnet->calls.next,
-					  struct rxrpc_call, link);
-			_debug("Zapping call %p", call);
-
-			rxrpc_see_call(call, rxrpc_call_see_zap);
-			list_del_init(&call->link);
+		list_for_each_entry(call, &rxnet->calls, link) {
+			rxrpc_see_call(call, rxrpc_call_see_still_live);
 
 			pr_err("Call %p still in use (%d,%s,%lx,%lx)!\n",
 			       call, refcount_read(&call->ref),
 			       rxrpc_call_states[__rxrpc_call_state(call)],
 			       call->flags, call->events);
 
-			spin_unlock(&rxnet->call_lock);
-			cond_resched();
-			spin_lock(&rxnet->call_lock);
+			if (++shown >= 10)
+				break;
 		}
 
 		spin_unlock(&rxnet->call_lock);