* [PATCH v1] NFC: reorganize the functions in nci_request
@ 2021-11-15 14:56 Lin Ma
2021-11-15 14:57 ` CHANGELOG: " Lin Ma
2021-11-18 4:30 ` patchwork-bot+netdevbpf
0 siblings, 2 replies; 4+ messages in thread
From: Lin Ma @ 2021-11-15 14:56 UTC (permalink / raw)
To: netdev
Cc: krzysztof.kozlowski, davem, kuba, jirislaby, gregkh,
linux-kernel, Lin Ma
There is a possible data race as shown below:
thread-A in nci_request() | thread-B in nci_close_device()
| mutex_lock(&ndev->req_lock);
test_bit(NCI_UP, &ndev->flags); |
... | test_and_clear_bit(NCI_UP, &ndev->flags)
mutex_lock(&ndev->req_lock); |
|
This race will allow __nci_request() to be awaked while the device is
getting removed.
Similar to commit e2cb6b891ad2 ("bluetooth: eliminate the potential race
condition when removing the HCI controller"). this patch alters the
function sequence in nci_request() to prevent the data races between the
nci_close_device().
Signed-off-by: Lin Ma <linma@zju.edu.cn>
Fixes: 6a2968aaf50c ("NFC: basic NCI protocol implementation")
---
net/nfc/nci/core.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/net/nfc/nci/core.c b/net/nfc/nci/core.c
index 6fd873aa86be..1dd0269c1a72 100644
--- a/net/nfc/nci/core.c
+++ b/net/nfc/nci/core.c
@@ -144,12 +144,15 @@ inline int nci_request(struct nci_dev *ndev,
{
int rc;
- if (!test_bit(NCI_UP, &ndev->flags))
- return -ENETDOWN;
-
/* Serialize all requests */
mutex_lock(&ndev->req_lock);
- rc = __nci_request(ndev, req, opt, timeout);
+ /* check the state after obtaing the lock against any races
+ * from nci_close_device when the device gets removed.
+ */
+ if (test_bit(NCI_UP, &ndev->flags))
+ rc = __nci_request(ndev, req, opt, timeout);
+ else
+ rc = -ENETDOWN;
mutex_unlock(&ndev->req_lock);
return rc;
--
2.33.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* CHANGELOG: [PATCH v1] NFC: reorganize the functions in nci_request
2021-11-15 14:56 [PATCH v1] NFC: reorganize the functions in nci_request Lin Ma
@ 2021-11-15 14:57 ` Lin Ma
2021-11-17 9:32 ` Krzysztof Kozlowski
2021-11-18 4:30 ` patchwork-bot+netdevbpf
1 sibling, 1 reply; 4+ messages in thread
From: Lin Ma @ 2021-11-15 14:57 UTC (permalink / raw)
To: netdev; +Cc: krzysztof.kozlowski, davem, kuba, jirislaby, gregkh, linux-kernel
Hi there,
Compared to the version-0 patch, this patch add fixes tag in the patch file
+ Fixes: 6a2968aaf50c ("NFC: basic NCI protocol implementation")
Best regards
Lin
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: CHANGELOG: [PATCH v1] NFC: reorganize the functions in nci_request
2021-11-15 14:57 ` CHANGELOG: " Lin Ma
@ 2021-11-17 9:32 ` Krzysztof Kozlowski
0 siblings, 0 replies; 4+ messages in thread
From: Krzysztof Kozlowski @ 2021-11-17 9:32 UTC (permalink / raw)
To: Lin Ma, netdev; +Cc: davem, kuba, jirislaby, gregkh, linux-kernel
On 15/11/2021 15:57, Lin Ma wrote:
> Hi there,
>
> Compared to the version-0 patch, this patch add fixes tag in the patch file
>
> + Fixes: 6a2968aaf50c ("NFC: basic NCI protocol implementation")
Changelog goes either as cover letter (git help format-patch) or after
'---' separator to individual patch.
Best regards,
Krzysztof
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v1] NFC: reorganize the functions in nci_request
2021-11-15 14:56 [PATCH v1] NFC: reorganize the functions in nci_request Lin Ma
2021-11-15 14:57 ` CHANGELOG: " Lin Ma
@ 2021-11-18 4:30 ` patchwork-bot+netdevbpf
1 sibling, 0 replies; 4+ messages in thread
From: patchwork-bot+netdevbpf @ 2021-11-18 4:30 UTC (permalink / raw)
To: Lin Ma
Cc: netdev, krzysztof.kozlowski, davem, kuba, jirislaby, gregkh,
linux-kernel
Hello:
This patch was applied to netdev/net.git (master)
by Jakub Kicinski <kuba@kernel.org>:
On Mon, 15 Nov 2021 22:56:00 +0800 you wrote:
> There is a possible data race as shown below:
>
> thread-A in nci_request() | thread-B in nci_close_device()
> | mutex_lock(&ndev->req_lock);
> test_bit(NCI_UP, &ndev->flags); |
> ... | test_and_clear_bit(NCI_UP, &ndev->flags)
> mutex_lock(&ndev->req_lock); |
> |
>
> [...]
Here is the summary with links:
- [v1] NFC: reorganize the functions in nci_request
https://git.kernel.org/netdev/net/c/86cdf8e38792
You are awesome, thank you!
--
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2021-11-15 14:57 ` CHANGELOG: " Lin Ma
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2021-11-18 4:30 ` patchwork-bot+netdevbpf
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