2018-12-26 16:17:14

by Jia-Ju Bai

Subject: [PATCH] isdn: hisax: hfc_pci: Fix a possible concurrency use-after-free bug in HFCPCI_l1hw()

In drivers/isdn/hisax/hfc_pci.c, the functions hfcpci_interrupt() and
HFCPCI_l1hw() may be concurrently executed.

HFCPCI_l1hw()
line 1173: if (!cs->tx_skb)

hfcpci_interrupt()
line 942: spin_lock_irqsave();
line 1066: dev_kfree_skb_irq(cs->tx_skb);

Thus, a possible concurrency use-after-free bug may occur
in HFCPCI_l1hw().

To fix these bugs, the calls to spin_lock_irqsave() and
spin_unlock_irqrestore() are added in HFCPCI_l1hw(), to protect the
access to cs->tx_skb.

Signed-off-by: Jia-Ju Bai <[email protected]>
---
drivers/isdn/hisax/hfc_pci.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/isdn/hisax/hfc_pci.c b/drivers/isdn/hisax/hfc_pci.c
index ea0e4c6de3fb..0109e0e8bcb6 100644
--- a/drivers/isdn/hisax/hfc_pci.c
+++ b/drivers/isdn/hisax/hfc_pci.c
@@ -1170,11 +1170,13 @@ HFCPCI_l1hw(struct PStack *st, int pr, void *arg)
if (cs->debug & L1_DEB_LAPD)
debugl1(cs, "-> PH_REQUEST_PULL");
#endif
+ spin_lock_irqsave(&cs->lock, flags);
if (!cs->tx_skb) {
test_and_clear_bit(FLG_L1_PULL_REQ, &st->l1.Flags);
st->l1.l1l2(st, PH_PULL | CONFIRM, NULL);
} else
test_and_set_bit(FLG_L1_PULL_REQ, &st->l1.Flags);
+ spin_unlock_irqrestore(&cs->lock, flags);
break;
case (HW_RESET | REQUEST):
spin_lock_irqsave(&cs->lock, flags);
--
2.17.0

2018-12-29 12:59:12

by David Miller

Subject: Re: [PATCH] isdn: hisax: hfc_pci: Fix a possible concurrency use-after-free bug in HFCPCI_l1hw()

From: Jia-Ju Bai <[email protected]>
Date: Wed, 26 Dec 2018 22:09:34 +0800

> In drivers/isdn/hisax/hfc_pci.c, the functions hfcpci_interrupt() and
> HFCPCI_l1hw() may be concurrently executed.
>
> HFCPCI_l1hw()
> line 1173: if (!cs->tx_skb)
>
> hfcpci_interrupt()
> line 942: spin_lock_irqsave();
> line 1066: dev_kfree_skb_irq(cs->tx_skb);
>
> Thus, a possible concurrency use-after-free bug may occur
> in HFCPCI_l1hw().
>
> To fix these bugs, the calls to spin_lock_irqsave() and
> spin_unlock_irqrestore() are added in HFCPCI_l1hw(), to protect the
> access to cs->tx_skb.
>
> Signed-off-by: Jia-Ju Bai <[email protected]>

Applied.