firewire: fix potential uaf in outbound_phy_packet_callback()

commit b7c81f80246fac44077166f3e07103affe6db8ff upstream.

&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@vger.kernel.org>
Signed-off-by: Chengfeng Ye <cyeaa@connect.ust.hk>
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20220409041243.603210-2-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/firewire/core-cdev.c b/drivers/firewire/core-cdev.c
index fb6c651..b0cc3f1 100644 (file)
--- a/drivers/firewire/core-cdev.c
+++ b/drivers/firewire/core-cdev.c
@@ -1480,6 +1480,7 @@ 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: */
@@ -1496,9 +1497,10 @@ 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)