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

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Message-Id: <20211104153253.23941-1-cyeaa@connect.ust.hk>
Date:   Thu,  4 Nov 2021 08:32:53 -0700
From:   Chengfeng Ye <cyeaa@...nect.ust.hk>
To:     stefanr@...6.in-berlin.de
Cc:     linux1394-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, Chengfeng Ye <cyeaa@...nect.ust.hk>
Subject: [PATCH] firewire: fix potential uaf in outbound_phy_packet_callback()

&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.

Signed-off-by: Chengfeng Ye <cyeaa@...nect.ust.hk>
---
 drivers/firewire/core-cdev.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/firewire/core-cdev.c b/drivers/firewire/core-cdev.c
index 9f89c17730b1..2f47e31918f0 100644
--- a/drivers/firewire/core-cdev.c
+++ b/drivers/firewire/core-cdev.c
@@ -1516,9 +1516,10 @@ static void outbound_phy_packet_callback(struct fw_packet *packet,
 	}
 	e->phy_packet.data[0] = packet->timestamp;
 
+	struct client *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)
-- 
2.17.1