| Message ID | 1559119739-27588-1-git-send-email-92siuyang@gmail.com |
|---|---|
| State | Rejected |
| Delegated to: | David Miller |
| Headers | show |
| Series | isdn: hisax: isac: fix a possible concurrency use-after-free bug in ISAC_l1hw() | expand |
From: Young Xiao <92siuyang@gmail.com> Date: Wed, 29 May 2019 16:48:59 +0800 > In drivers/isdn/hisax/isac.c, the function isac_interrupt() and > ISAC_l1hw() may be concurrently executed. > > ISAC_l1hw() > line 499: if (!cs->tx_skb) > > isac_interrupt() > line 250: dev_kfree_skb_irq(cs->tx_skb); > > Thus, a possible concurrency use-after-free bug may occur in ISAC_l1hw(). ... > + 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); Nothing in this code accesses the cs->tx_skb object. It is just a logic test upon whether it is NULL or not. I'm not applying stuff like this, sorry. You have to show how something can actually go wrong when fixing a bug.
diff --git a/drivers/isdn/hisax/isac.c b/drivers/isdn/hisax/isac.c index bd40e06..60dd805 100644 --- a/drivers/isdn/hisax/isac.c +++ b/drivers/isdn/hisax/isac.c @@ -496,11 +496,13 @@ ISAC_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);
In drivers/isdn/hisax/isac.c, the function isac_interrupt() and ISAC_l1hw() may be concurrently executed. ISAC_l1hw() line 499: if (!cs->tx_skb) isac_interrupt() line 250: dev_kfree_skb_irq(cs->tx_skb); Thus, a possible concurrency use-after-free bug may occur in ISAC_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. See commit 7418e6520f22 ("isdn: hisax: hfc_pci: Fix a possible concurrency use-after-free bug in HFCPCI_l1hw()") for details. Signed-off-by: Young Xiao <92siuyang@gmail.com> --- drivers/isdn/hisax/isac.c | 2 ++ 1 file changed, 2 insertions(+)