linux-kernel - [PATCH] vmci: prevent speculation leaks by sanitizing event in event

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Message-ID: <20231127193533.46174-1-hagarhem@amazon.com>
Date:   Mon, 27 Nov 2023 19:35:33 +0000
From:   Hagar Gamal Halim Hemdan <hagarhem@...zon.com>
To:     unlisted-recipients:; (no To-header on input)
CC:     <stable@...r.kernel.org>,
        Hagar Gamal Halim Hemdan <hagarhem@...zon.com>,
        Bryan Tan <bryantan@...are.com>,
        Vishnu Dasa <vdasa@...are.com>,
        "VMware PV-Drivers Reviewers" <pv-drivers@...are.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Dmitry Torokhov <dtor@...are.com>,
        George Zhang <georgezhang@...are.com>,
        Andy king <acking@...are.com>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] vmci: prevent speculation leaks by sanitizing event in event_deliver()

Coverity spotted that event_msg is controlled by user-space,
event_msg->event_data.event is passed to event_deliver() and used
as an index without sanitization.

This change ensures that the event index is sanitized to mitigate any
possibility of speculative information leaks.

Fixes: 1d990201f9bb ("VMCI: event handling implementation.")

Signed-off-by: Hagar Gamal Halim Hemdan <hagarhem@...zon.com>
---
 drivers/misc/vmw_vmci/vmci_event.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/misc/vmw_vmci/vmci_event.c b/drivers/misc/vmw_vmci/vmci_event.c
index 5d7ac07623c2..9a41ab65378d 100644
--- a/drivers/misc/vmw_vmci/vmci_event.c
+++ b/drivers/misc/vmw_vmci/vmci_event.c
@@ -9,6 +9,7 @@
 #include <linux/vmw_vmci_api.h>
 #include <linux/list.h>
 #include <linux/module.h>
+#include <linux/nospec.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/rculist.h>
@@ -86,9 +87,12 @@ static void event_deliver(struct vmci_event_msg *event_msg)
 {
 	struct vmci_subscription *cur;
 	struct list_head *subscriber_list;
+	u32 sanitized_event, max_vmci_event;
 
 	rcu_read_lock();
-	subscriber_list = &subscriber_array[event_msg->event_data.event];
+	max_vmci_event = ARRAY_SIZE(subscriber_array);
+	sanitized_event = array_index_nospec(event_msg->event_data.event, max_vmci_event);
+	subscriber_list = &subscriber_array[sanitized_event];
 	list_for_each_entry_rcu(cur, subscriber_list, node) {
 		cur->callback(cur->id, &event_msg->event_data,
 			      cur->callback_data);
-- 
2.40.1