2023-12-07 12:35:02

by Chengfeng Ye

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Subject: [PATCH v3 1/2] atm: solos-pci: Fix potential deadlock on &cli_queue_lock

As &card->cli_queue_lock is acquired under softirq context along the
following call chain from solos_bh(), other acquisition of the same
lock inside process context should disable at least bh to avoid double
lock.

<deadlock #1>
console_show()
--> spin_lock(&card->cli_queue_lock)
<interrupt>
--> solos_bh()
--> spin_lock(&card->cli_queue_lock)

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

To prevent the potential deadlock, the patch uses spin_lock_bh()
on the card->cli_queue_lock under process context code consistently
to prevent the possible deadlock scenario.

Fixes: 9c54004ea717 ("atm: Driver for Solos PCI ADSL2+ card.")
Signed-off-by: Chengfeng Ye <[email protected]>
---
V3: change to spin_lock_bh()
V2: add fix tag, and slipt into two patches

drivers/atm/solos-pci.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/atm/solos-pci.c b/drivers/atm/solos-pci.c
index 94fbc3abe60e..95f768b28a5e 100644
--- a/drivers/atm/solos-pci.c
+++ b/drivers/atm/solos-pci.c
@@ -449,9 +449,9 @@ static ssize_t console_show(struct device *dev, struct device_attribute *attr,
struct sk_buff *skb;
unsigned int len;

- spin_lock(&card->cli_queue_lock);
+ spin_lock_bh(&card->cli_queue_lock);
skb = skb_dequeue(&card->cli_queue[SOLOS_CHAN(atmdev)]);
- spin_unlock(&card->cli_queue_lock);
+ spin_unlock_bh(&card->cli_queue_lock);
if(skb == NULL)
return sprintf(buf, "No data.\n");

--
2.17.1


2023-12-12 18:23:17

by Jakub Kicinski

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Subject: Re: [PATCH v3 1/2] atm: solos-pci: Fix potential deadlock on &cli_queue_lock

On Thu, 7 Dec 2023 12:34:37 +0000 Chengfeng Ye wrote:
> As &card->cli_queue_lock is acquired under softirq context along the
> following call chain from solos_bh(), other acquisition of the same
> lock inside process context should disable at least bh to avoid double
> lock.

These appear to have been applied to net, thanks!

2023-12-12 18:26:33

by Chengfeng Ye

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