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authorOliver Hartkopp <socketcan@hartkopp.net>2022-02-08 21:00:26 +0100
committerMarc Kleine-Budde <mkl@pengutronix.de>2022-02-09 08:47:25 +0100
commit7c759040c1dd03954f650f147ae7175476d51314 (patch)
tree5440bad5b937aeb8c29bfafc687e4894324584f0
parent7db788ad627aabff2b74d4f1a3b68516d0fee0d7 (diff)
can: isotp: fix potential CAN frame reception race in isotp_rcv()
When receiving a CAN frame the current code logic does not consider concurrently receiving processes which do not show up in real world usage. Ziyang Xuan writes: The following syz problem is one of the scenarios. so->rx.len is changed by isotp_rcv_ff() during isotp_rcv_cf(), so->rx.len equals 0 before alloc_skb() and equals 4096 after alloc_skb(). That will trigger skb_over_panic() in skb_put(). ======================================================= CPU: 1 PID: 19 Comm: ksoftirqd/1 Not tainted 5.16.0-rc8-syzkaller #0 RIP: 0010:skb_panic+0x16c/0x16e net/core/skbuff.c:113 Call Trace: <TASK> skb_over_panic net/core/skbuff.c:118 [inline] skb_put.cold+0x24/0x24 net/core/skbuff.c:1990 isotp_rcv_cf net/can/isotp.c:570 [inline] isotp_rcv+0xa38/0x1e30 net/can/isotp.c:668 deliver net/can/af_can.c:574 [inline] can_rcv_filter+0x445/0x8d0 net/can/af_can.c:635 can_receive+0x31d/0x580 net/can/af_can.c:665 can_rcv+0x120/0x1c0 net/can/af_can.c:696 __netif_receive_skb_one_core+0x114/0x180 net/core/dev.c:5465 __netif_receive_skb+0x24/0x1b0 net/core/dev.c:5579 Therefore we make sure the state changes and data structures stay consistent at CAN frame reception time by adding a spin_lock in isotp_rcv(). This fixes the issue reported by syzkaller but does not affect real world operation. Fixes: e057dd3fc20f ("can: add ISO 15765-2:2016 transport protocol") Link: https://lore.kernel.org/linux-can/d7e69278-d741-c706-65e1-e87623d9a8e8@huawei.com/T/ Link: https://lore.kernel.org/all/20220208200026.13783-1-socketcan@hartkopp.net Cc: stable@vger.kernel.org Reported-by: syzbot+4c63f36709a642f801c5@syzkaller.appspotmail.com Reported-by: Ziyang Xuan <william.xuanziyang@huawei.com> Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
-rw-r--r--net/can/isotp.c14
1 files changed, 13 insertions, 1 deletions
diff --git a/net/can/isotp.c b/net/can/isotp.c
index 02cbcb2ecf0d..9149e8d8aefc 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -56,6 +56,7 @@
#include <linux/module.h>
#include <linux/init.h>
#include <linux/interrupt.h>
+#include <linux/spinlock.h>
#include <linux/hrtimer.h>
#include <linux/wait.h>
#include <linux/uio.h>
@@ -145,6 +146,7 @@ struct isotp_sock {
struct tpcon rx, tx;
struct list_head notifier;
wait_queue_head_t wait;
+ spinlock_t rx_lock; /* protect single thread state machine */
};
static LIST_HEAD(isotp_notifier_list);
@@ -615,11 +617,17 @@ static void isotp_rcv(struct sk_buff *skb, void *data)
n_pci_type = cf->data[ae] & 0xF0;
+ /* Make sure the state changes and data structures stay consistent at
+ * CAN frame reception time. This locking is not needed in real world
+ * use cases but the inconsistency can be triggered with syzkaller.
+ */
+ spin_lock(&so->rx_lock);
+
if (so->opt.flags & CAN_ISOTP_HALF_DUPLEX) {
/* check rx/tx path half duplex expectations */
if ((so->tx.state != ISOTP_IDLE && n_pci_type != N_PCI_FC) ||
(so->rx.state != ISOTP_IDLE && n_pci_type == N_PCI_FC))
- return;
+ goto out_unlock;
}
switch (n_pci_type) {
@@ -668,6 +676,9 @@ static void isotp_rcv(struct sk_buff *skb, void *data)
isotp_rcv_cf(sk, cf, ae, skb);
break;
}
+
+out_unlock:
+ spin_unlock(&so->rx_lock);
}
static void isotp_fill_dataframe(struct canfd_frame *cf, struct isotp_sock *so,
@@ -1444,6 +1455,7 @@ static int isotp_init(struct sock *sk)
so->txtimer.function = isotp_tx_timer_handler;
init_waitqueue_head(&so->wait);
+ spin_lock_init(&so->rx_lock);
spin_lock(&isotp_notifier_lock);
list_add_tail(&so->notifier, &isotp_notifier_list);