2018-12-27 16:17:41

by Jia-Ju Bai

Subject: [PATCH v2] net: arcnet: Fix a possible concurrency use-after-free bug in arcnet_reply_tasklet()

In drivers/net/arcnet/arcnet.c, the functions arcnet_reply_tasklet() and
arcnet_send_packet() may be concurrently executed.

arcnet_reply_tasklet()
line 430: dev_kfree_skb(lp->outgoing.skb);

arcnet_send_packet()
line 682: spin_lock_irqsave();
line 690: lp->outgoing.skb = skb;
line 691: proto->prepare_tx(..., skb->len, ...)

Thus, a possible concurrency use-after-free bugs may occur.

To fix this bug, the calls to spin_lock_irqsave() and
spin_unlock_irqrestore() are added in arcnet_reply_tasklet() to protect
dev_kfree_skb(lp->outgoing.skb).


Signed-off-by: Jia-Ju Bai <[email protected]>
---
v2:
* Add the definition of flags to fix the compilation error.
---
drivers/net/arcnet/arcnet.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/drivers/net/arcnet/arcnet.c b/drivers/net/arcnet/arcnet.c
index 8459115d9d4e..1e1b12650964 100644
--- a/drivers/net/arcnet/arcnet.c
+++ b/drivers/net/arcnet/arcnet.c
@@ -401,6 +401,7 @@ static void arcnet_reply_tasklet(unsigned long data)
struct sock_exterr_skb *serr;
struct sock *sk;
int ret;
+ unsigned long flags;

local_irq_disable();
skb = lp->outgoing.skb;
@@ -426,10 +427,14 @@ static void arcnet_reply_tasklet(unsigned long data)
serr->ee.ee_data = skb_shinfo(skb)->tskey;
serr->ee.ee_info = lp->reply_status;

+ spin_lock_irqsave(&lp->lock, flags);
+
/* finally erasing outgoing skb */
dev_kfree_skb(lp->outgoing.skb);
lp->outgoing.skb = NULL;

+ spin_unlock_irqrestore(&lp->lock, flags);
+
ackskb->dev = lp->dev;

ret = sock_queue_err_skb(sk, ackskb);
--
2.17.0

2018-12-29 12:59:22

by David Miller

Subject: Re: [PATCH v2] net: arcnet: Fix a possible concurrency use-after-free bug in arcnet_reply_tasklet()

From: Jia-Ju Bai <[email protected]>
Date: Thu, 27 Dec 2018 10:01:42 +0800

> @@ -401,6 +401,7 @@ static void arcnet_reply_tasklet(unsigned long data)
> struct sock_exterr_skb *serr;
> struct sock *sk;
> int ret;
> + unsigned long flags;
>
> local_irq_disable();
> skb = lp->outgoing.skb;
> @@ -426,10 +427,14 @@ static void arcnet_reply_tasklet(unsigned long data)
> serr->ee.ee_data = skb_shinfo(skb)->tskey;
> serr->ee.ee_info = lp->reply_status;
>
> + spin_lock_irqsave(&lp->lock, flags);
> +
> /* finally erasing outgoing skb */
> dev_kfree_skb(lp->outgoing.skb);
> lp->outgoing.skb = NULL;
>
> + spin_unlock_irqrestore(&lp->lock, flags);
> +
> ackskb->dev = lp->dev;
>
> ret = sock_queue_err_skb(sk, ackskb);

This is not the correct fix.

You need to instead replace the existing local_irq_*() calls in the
function with the spinlock stuff.