[PATCH 6.1 033/127] mISDN: hfcpci: Fix potential deadlock on &hc->lock

Greg Kroah-Hartman
2023-08-09T10:52:48Z

From: Chengfeng Ye <dg573847474@gmail.com>

[ Upstream commit 56c6be35fcbed54279df0a2c9e60480a61841d6f ]

As &hc->lock is acquired by both timer _hfcpci_softirq() and hardirq
hfcpci_int(), the timer should disable irq before lock acquisition
otherwise deadlock could happen if the timmer is preemtped by the hadr irq.

Possible deadlock scenario:
hfcpci_softirq() (timer)
-> _hfcpci_softirq()
-> spin_lock(&hc->lock);
<irq interruption>
-> hfcpci_int()
-> spin_lock(&hc->lock); (deadlock here)

This flaw was found by an experimental static analysis tool I am developing
for irq-related deadlock.

The tentative patch fixes the potential deadlock by spin_lock_irq()
in timer.

Fixes: b36b654a7e82 ("mISDN: Create /sys/class/mISDN")
Signed-off-by: Chengfeng Ye <dg573847474@gmail.com>
Link: https://lore.kernel.org/r/20230727085619.7419-1-dg573847474@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/isdn/hardware/mISDN/hfcpci.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/isdn/hardware/mISDN/hfcpci.c b/drivers/isdn/hardware/mISDN/hfcpci.c
index c0331b2680108..fe391de1aba32 100644
--- a/drivers/isdn/hardware/mISDN/hfcpci.c
+++ b/drivers/isdn/hardware/mISDN/hfcpci.c
@@ -839,7 +839,7 @@ hfcpci_fill_fifo(struct bchannel *bch)
*z1t = cpu_to_le16(new_z1); /* now send data */
if (bch->tx_idx < bch->tx_skb->len)
return;
- dev_kfree_skb(bch->tx_skb);
+ dev_kfree_skb_any(bch->tx_skb);
if (get_next_bframe(bch))
goto next_t_frame;
return;
@@ -895,7 +895,7 @@ hfcpci_fill_fifo(struct bchannel *bch)
}
bz->za[new_f1].z1 = cpu_to_le16(new_z1); /* for next buffer */
bz->f1 = new_f1; /* next frame */
- dev_kfree_skb(bch->tx_skb);
+ dev_kfree_skb_any(bch->tx_skb);
get_next_bframe(bch);
}

@@ -1119,7 +1119,7 @@ tx_birq(struct bchannel *bch)
if (bch->tx_skb && bch->tx_idx < bch->tx_skb->len)
hfcpci_fill_fifo(bch);
else {
- dev_kfree_skb(bch->tx_skb);
+ dev_kfree_skb_any(bch->tx_skb);
if (get_next_bframe(bch))
hfcpci_fill_fifo(bch);
}
@@ -2277,7 +2277,7 @@ _hfcpci_softirq(struct device *dev, void *unused)
return 0;

if (hc->hw.int_m2 & HFCPCI_IRQ_ENABLE) {
- spin_lock(&hc->lock);
+ spin_lock_irq(&hc->lock);
bch = Sel_BCS(hc, hc->hw.bswapped ? 2 : 1);
if (bch && bch->state == ISDN_P_B_RAW) { /* B1 rx&tx */
main_rec_hfcpci(bch);
@@ -2288,7 +2288,7 @@ _hfcpci_softirq(struct device *dev, void *unused)
main_rec_hfcpci(bch);
tx_birq(bch);
}
- spin_unlock(&hc->lock);
+ spin_unlock_irq(&hc->lock);
}
return 0;
}
--
2.40.1