ipmi: Fix user refcount underflow in event delivery

ipmi_alloc_recv_msg(user) takes the temporary user reference owned by the
receive message, and ipmi_free_recv_msg() drops it again. If event delivery
fails after allocating receive messages for earlier users,
handle_read_event_rsp() rolls those messages back with
ipmi_free_recv_msg().

That rollback path still drops user->refcount explicitly after freeing each
message. The extra put can free a user that remains linked on intf->users,
so later event delivery may dereference a freed user or trip refcount_t's
addition-on-zero warning when ipmi_alloc_recv_msg() tries to acquire
another reference.

Remove the stale explicit put and the now-dead user assignment. Keep the
list_del() and ipmi_free_recv_msg() calls; they are the required rollback
operations.

Fixes: b52da4054ee0 ("ipmi: Rework user message limit handling")
Cc: stable@vger.kernel.org # v6.18+
Signed-off-by: Matt Fleming <mfleming@cloudflare.com>
Message-ID: <20260521130628.3641050-1-matt@readmodwrite.com>
Signed-off-by: Corey Minyard <corey@minyard.net>

diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
index 7a4566046b68c1b720821e0cfa2f19ec668e256b..7ca2cacbaa051230ae2ff1961182ca8fa3f41265 100644 (file)
--- a/drivers/char/ipmi/ipmi_msghandler.c
+++ b/drivers/char/ipmi/ipmi_msghandler.c
@@ -4472,10 +4472,8 @@ static int handle_read_event_rsp(struct ipmi_smi *intf,
                        mutex_unlock(&intf->users_mutex);
                        list_for_each_entry_safe(recv_msg, recv_msg2, &msgs,
                                                 link) {
-                               user = recv_msg->user;
                                list_del(&recv_msg->link);
                                ipmi_free_recv_msg(recv_msg);
-                               kref_put(&user->refcount, free_ipmi_user);
                        }
                        /*
                         * We couldn't allocate memory for the