2022-04-05 02:25:08

by Niels Dossche

Subject: [PATCH] Bluetooth: use hdev lock for accept_list and reject_list in conn req

All accesses (both read and modifications) to
hdev->{accept,reject}_list are protected by hdev lock,
except the ones in hci_conn_request_evt. This can cause a race condition
in the form of a list corruption.
The solution is to protect these lists in hci_conn_request_evt as well.

I was unable to find the exact commit that introduced the issue for the
reject list, I was only able to find it for the accept list.

Note:
I am currently working on a static analyser to detect missing locks
using type-based static analysis as my master's thesis
in order to obtain my master's degree.
If you would like to have more details, please let me know.
This was a reported case. I manually verified the report by looking
at the code, so that I do not send wrong information or patches.
After concluding that this seems to be a true positive, I created
this patch. I have both compile-tested this patch and runtime-tested
this patch on x86_64. The effect on a running system could be a
potential race condition in exceptional cases.
This issue was found on Linux v5.17.1.

Fixes: a55bd29d5227 ("Bluetooth: Add white list lookup for incoming connection requests")
Signed-off-by: Niels Dossche <[email protected]>
---
net/bluetooth/hci_event.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index abaabfae19cc..b9038f24f46f 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -3222,8 +3222,11 @@ static void hci_conn_request_evt(struct hci_dev *hdev, void *data,
return;
}

+ hci_dev_lock(hdev);
+
if (hci_bdaddr_list_lookup(&hdev->reject_list, &ev->bdaddr,
BDADDR_BREDR)) {
+ hci_dev_unlock(hdev);
hci_reject_conn(hdev, &ev->bdaddr);
return;
}
@@ -3236,14 +3239,13 @@ static void hci_conn_request_evt(struct hci_dev *hdev, void *data,
!hci_dev_test_flag(hdev, HCI_CONNECTABLE) &&
!hci_bdaddr_list_lookup_with_flags(&hdev->accept_list, &ev->bdaddr,
BDADDR_BREDR)) {
+ hci_dev_unlock(hdev);
hci_reject_conn(hdev, &ev->bdaddr);
return;
}

/* Connection accepted */

- hci_dev_lock(hdev);
-
ie = hci_inquiry_cache_lookup(hdev, &ev->bdaddr);
if (ie)
memcpy(ie->data.dev_class, ev->dev_class, 3);
--
2.35.1

2022-04-06 11:27:27

by Marcel Holtmann

Subject: Re: [PATCH] Bluetooth: use hdev lock for accept_list and reject_list in conn req

Hi Niels,

> All accesses (both read and modifications) to
> hdev->{accept,reject}_list are protected by hdev lock,
> except the ones in hci_conn_request_evt. This can cause a race condition
> in the form of a list corruption.
> The solution is to protect these lists in hci_conn_request_evt as well.
>
> I was unable to find the exact commit that introduced the issue for the
> reject list, I was only able to find it for the accept list.
>
> Note:
> I am currently working on a static analyser to detect missing locks
> using type-based static analysis as my master's thesis
> in order to obtain my master's degree.
> If you would like to have more details, please let me know.
> This was a reported case. I manually verified the report by looking
> at the code, so that I do not send wrong information or patches.
> After concluding that this seems to be a true positive, I created
> this patch. I have both compile-tested this patch and runtime-tested
> this patch on x86_64. The effect on a running system could be a
> potential race condition in exceptional cases.
> This issue was found on Linux v5.17.1.

this doesn’t belong in the commit message.

>
> Fixes: a55bd29d5227 ("Bluetooth: Add white list lookup for incoming connection requests")
> Signed-off-by: Niels Dossche <[email protected]>
> ---
> net/bluetooth/hci_event.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> index abaabfae19cc..b9038f24f46f 100644
> --- a/net/bluetooth/hci_event.c
> +++ b/net/bluetooth/hci_event.c
> @@ -3222,8 +3222,11 @@ static void hci_conn_request_evt(struct hci_dev *hdev, void *data,
> return;
> }
>
> + hci_dev_lock(hdev);
> +
> if (hci_bdaddr_list_lookup(&hdev->reject_list, &ev->bdaddr,
> BDADDR_BREDR)) {
> + hci_dev_unlock(hdev);
> hci_reject_conn(hdev, &ev->bdaddr);
> return;
> }
> @@ -3236,14 +3239,13 @@ static void hci_conn_request_evt(struct hci_dev *hdev, void *data,
> !hci_dev_test_flag(hdev, HCI_CONNECTABLE) &&
> !hci_bdaddr_list_lookup_with_flags(&hdev->accept_list, &ev->bdaddr,
> BDADDR_BREDR)) {
> + hci_dev_unlock(hdev);
> hci_reject_conn(hdev, &ev->bdaddr);
> return;
> }

Can we use an exit goto-label instead. I am not a big fan of "unbalanced” _unlock statements.

> /* Connection accepted */
>
> - hci_dev_lock(hdev);
> -
> ie = hci_inquiry_cache_lookup(hdev, &ev->bdaddr);
> if (ie)
> memcpy(ie->data.dev_class, ev->dev_class, 3);

Regards

Marcel

2022-04-06 11:54:03

by Niels Dossche

Subject: Re: [PATCH] Bluetooth: use hdev lock for accept_list and reject_list in conn req

On 05/04/2022 19:18, Marcel Holtmann wrote:
> Hi Niels,
>
>> All accesses (both read and modifications) to
>> hdev->{accept,reject}_list are protected by hdev lock,
>> except the ones in hci_conn_request_evt. This can cause a race condition
>> in the form of a list corruption.
>> The solution is to protect these lists in hci_conn_request_evt as well.
>>
>> I was unable to find the exact commit that introduced the issue for the
>> reject list, I was only able to find it for the accept list.
>>
>> Note:
>> I am currently working on a static analyser to detect missing locks
>> using type-based static analysis as my master's thesis
>> in order to obtain my master's degree.
>> If you would like to have more details, please let me know.
>> This was a reported case. I manually verified the report by looking
>> at the code, so that I do not send wrong information or patches.
>> After concluding that this seems to be a true positive, I created
>> this patch. I have both compile-tested this patch and runtime-tested
>> this patch on x86_64. The effect on a running system could be a
>> potential race condition in exceptional cases.
>> This issue was found on Linux v5.17.1.
>
> this doesn’t belong in the commit message.

Hi Marcel
I'll remove it from the commit message.
I can write it in below the --- in the future such that it won't be included.

>
>>
>> Fixes: a55bd29d5227 ("Bluetooth: Add white list lookup for incoming connection requests")
>> Signed-off-by: Niels Dossche <[email protected]>
>> ---
>> net/bluetooth/hci_event.c | 6 ++++--
>> 1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
>> index abaabfae19cc..b9038f24f46f 100644
>> --- a/net/bluetooth/hci_event.c
>> +++ b/net/bluetooth/hci_event.c
>> @@ -3222,8 +3222,11 @@ static void hci_conn_request_evt(struct hci_dev *hdev, void *data,
>> return;
>> }
>>
>> + hci_dev_lock(hdev);
>> +
>> if (hci_bdaddr_list_lookup(&hdev->reject_list, &ev->bdaddr,
>> BDADDR_BREDR)) {
>> + hci_dev_unlock(hdev);
>> hci_reject_conn(hdev, &ev->bdaddr);
>> return;
>> }
>> @@ -3236,14 +3239,13 @@ static void hci_conn_request_evt(struct hci_dev *hdev, void *data,
>> !hci_dev_test_flag(hdev, HCI_CONNECTABLE) &&
>> !hci_bdaddr_list_lookup_with_flags(&hdev->accept_list, &ev->bdaddr,
>> BDADDR_BREDR)) {
>> + hci_dev_unlock(hdev);
>> hci_reject_conn(hdev, &ev->bdaddr);
>> return;
>> }
>
> Can we use an exit goto-label instead. I am not a big fan of "unbalanced” _unlock statements.

I'll make a v2 and send it.

>
>> /* Connection accepted */
>>
>> - hci_dev_lock(hdev);
>> -
>> ie = hci_inquiry_cache_lookup(hdev, &ev->bdaddr);
>> if (ie)
>> memcpy(ie->data.dev_class, ev->dev_class, 3);
>
> Regards
>
> Marcel
>

Thanks
Niels