On 28.01.22 08:56, Marc Kleine-Budde wrote:
On 28.01.2022 08:43:27, Oliver Hartkopp wrote:
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.
Link: https://lore.kernel.org/linux-can/d7e69278-d741-c706-65e1-e87623d9a8e8@xxxxxxxxxx/T/
Fixes: e057dd3fc20f ("can: add ISO 15765-2:2016 transport protocol")
Reported-by: syzbot+4c63f36709a642f801c5@xxxxxxxxxxxxxxxxxxxxxxxxx
Reported-by: Ziyang Xuan <william.xuanziyang@xxxxxxxxxx>
Signed-off-by: Oliver Hartkopp <socketcan@xxxxxxxxxxxx>
---
net/can/isotp.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/net/can/isotp.c b/net/can/isotp.c
index 02cbcb2ecf0d..b5ba1a9a9e3b 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -54,10 +54,11 @@
*/
#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>
#include <linux/net.h>
#include <linux/netdevice.h>
@@ -143,10 +144,11 @@ struct isotp_sock {
u32 force_tx_stmin;
u32 force_rx_stmin;
struct tpcon rx, tx;
struct list_head notifier;
wait_queue_head_t wait;
+ spinlock_t rx_lock;
I think checkpatch wants to have a comment describing the lock.
Ok.
};
static LIST_HEAD(isotp_notifier_list);
static DEFINE_SPINLOCK(isotp_notifier_lock);
static struct isotp_sock *isotp_busy_notifier;
@@ -613,10 +615,19 @@ static void isotp_rcv(struct sk_buff *skb, void *data)
if (ae && cf->data[0] != so->opt.rx_ext_address)
return;
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.
+ *
+ * To not lock up the softirq just drop the frame in syzcaller case.
+ */
+ if (!spin_trylock(&so->rx_lock))
+ return;
+
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;
Maybe there are more returns, which are not shown in the context of this
patch.
Oh, yes! Thanks!
Will send a V3 soon.
@@ -666,10 +677,12 @@ static void isotp_rcv(struct sk_buff *skb, void *data)
case N_PCI_CF:
/* rx path: consecutive frame */
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,
int ae, int off)
{
@@ -1442,10 +1455,11 @@ static int isotp_init(struct sock *sk)
so->rxtimer.function = isotp_rx_timer_handler;
hrtimer_init(&so->txtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_SOFT);
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);
spin_unlock(&isotp_notifier_lock);
regards,
Marc
