linux-kernel - [PATCH 1/3] firewire: fix potential uaf in outbound_phy_packet

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Date:   Sat,  9 Apr 2022 13:12:41 +0900
From:   Takashi Sakamoto <o-takashi@...amocchi.jp>
To:     tiwai@...e.de
Cc:     linux1394-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, alsa-devel@...a-project.org,
        Chengfeng Ye <cyeaa@...nect.ust.hk>, stable@...r.kernel.org
Subject: [PATCH 1/3] firewire: fix potential uaf in outbound_phy_packet_callback()

From: Chengfeng Ye <cyeaa@...nect.ust.hk>

&e->event and e point to the same address, and &e->event could
be freed in queue_event. So there is a potential uaf issue if
we dereference e after calling queue_event(). Fix this by adding
a temporary variable to maintain e->client in advance, this can
avoid the potential uaf issue.

Cc: <stable@...r.kernel.org>
Signed-off-by: Chengfeng Ye <cyeaa@...nect.ust.hk>
Signed-off-by: Takashi Sakamoto <o-takashi@...amocchi.jp>
---
 drivers/firewire/core-cdev.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/firewire/core-cdev.c b/drivers/firewire/core-cdev.c
index 9f89c17730b1..708e417200f4 100644
--- a/drivers/firewire/core-cdev.c
+++ b/drivers/firewire/core-cdev.c
@@ -1500,6 +1500,7 @@ static void outbound_phy_packet_callback(struct fw_packet *packet,
 {
 	struct outbound_phy_packet_event *e =
 		container_of(packet, struct outbound_phy_packet_event, p);
+	struct client *e_client;
 
 	switch (status) {
 	/* expected: */
@@ -1516,9 +1517,10 @@ static void outbound_phy_packet_callback(struct fw_packet *packet,
 	}
 	e->phy_packet.data[0] = packet->timestamp;
 
+	e_client = e->client;
 	queue_event(e->client, &e->event, &e->phy_packet,
 		    sizeof(e->phy_packet) + e->phy_packet.length, NULL, 0);
-	client_put(e->client);
+	client_put(e_client);
 }
 
 static int ioctl_send_phy_packet(struct client *client, union ioctl_arg *arg)
-- 
2.34.1