* [PATCH] net: bluetooth: hci_sock: Fix a possible null-pointer dereference in hci_mgmt_cmd()
@ 2019-07-25 9:22 Jia-Ju Bai
2019-07-25 9:39 ` Marcel Holtmann
0 siblings, 1 reply; 2+ messages in thread
From: Jia-Ju Bai @ 2019-07-25 9:22 UTC (permalink / raw)
To: marcel, johan.hedberg, davem
Cc: linux-bluetooth, netdev, linux-kernel, Jia-Ju Bai
In hci_mgmt_cmd(), there is an if statement on line 1570 to check
whether hdev is NULL:
if (hdev && chan->hdev_init)
When hdev is NULL, it is used on line 1575:
err = handler->func(sk, hdev, cp, len);
Some called functions of handler->func use hdev, such as:
set_appearance(), add_device() and remove_device() in mgmt.c.
Thus, a possible null-pointer dereference may occur.
To fix this bug, hdev is checked before calling handler->func().
This bug is found by a static analysis tool STCheck written by us.
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
net/bluetooth/hci_sock.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c
index d32077b28433..18ea1e47ea48 100644
--- a/net/bluetooth/hci_sock.c
+++ b/net/bluetooth/hci_sock.c
@@ -1570,11 +1570,12 @@ static int hci_mgmt_cmd(struct hci_mgmt_chan *chan, struct sock *sk,
if (hdev && chan->hdev_init)
chan->hdev_init(sk, hdev);
- cp = buf + sizeof(*hdr);
-
- err = handler->func(sk, hdev, cp, len);
- if (err < 0)
- goto done;
+ if (hdev) {
+ cp = buf + sizeof(*hdr);
+ err = handler->func(sk, hdev, cp, len);
+ if (err < 0)
+ goto done;
+ }
err = msglen;
--
2.17.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] net: bluetooth: hci_sock: Fix a possible null-pointer dereference in hci_mgmt_cmd()
2019-07-25 9:22 [PATCH] net: bluetooth: hci_sock: Fix a possible null-pointer dereference in hci_mgmt_cmd() Jia-Ju Bai
@ 2019-07-25 9:39 ` Marcel Holtmann
0 siblings, 0 replies; 2+ messages in thread
From: Marcel Holtmann @ 2019-07-25 9:39 UTC (permalink / raw)
To: Jia-Ju Bai
Cc: Johan Hedberg, David S. Miller, linux-bluetooth, netdev, linux-kernel
Hi Jia-Ju,
> In hci_mgmt_cmd(), there is an if statement on line 1570 to check
> whether hdev is NULL:
> if (hdev && chan->hdev_init)
>
> When hdev is NULL, it is used on line 1575:
> err = handler->func(sk, hdev, cp, len);
>
> Some called functions of handler->func use hdev, such as:
> set_appearance(), add_device() and remove_device() in mgmt.c.
>
> Thus, a possible null-pointer dereference may occur.
>
> To fix this bug, hdev is checked before calling handler->func().
>
> This bug is found by a static analysis tool STCheck written by us.
>
> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
> ---
> net/bluetooth/hci_sock.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c
> index d32077b28433..18ea1e47ea48 100644
> --- a/net/bluetooth/hci_sock.c
> +++ b/net/bluetooth/hci_sock.c
> @@ -1570,11 +1570,12 @@ static int hci_mgmt_cmd(struct hci_mgmt_chan *chan, struct sock *sk,
> if (hdev && chan->hdev_init)
> chan->hdev_init(sk, hdev);
>
> - cp = buf + sizeof(*hdr);
> -
> - err = handler->func(sk, hdev, cp, len);
> - if (err < 0)
> - goto done;
> + if (hdev) {
> + cp = buf + sizeof(*hdr);
> + err = handler->func(sk, hdev, cp, len);
> + if (err < 0)
> + goto done;
> + }
>
> err = msglen;
have you evaluated the statement above:
no_hdev = (handler->flags & HCI_MGMT_NO_HDEV);
if (no_hdev != !hdev) {
err = mgmt_cmd_status(sk, index, opcode,
MGMT_STATUS_INVALID_INDEX);
goto done;
}
I think that code is just overly complex and can be simplified, but I doubt you get to the situation where hdev is NULL for any function that requires it. Only the handler->func marked with HCI_MGMT_NO_HDEV will get hdev == NULL and these are not using it.
So we might can make this easier code to really check the index != MGMT_INDEX_NONE check above to cover all cases to ensure that hdev is either valid or set to NULL before proceeding any further.
And since we have a full set of unit tests in tools/mgmt-tester, I assume we would have had a chance to catch an issue like this. But we can add a test case to it to explicitly call the functions with either MGMT_INDEX_NONE used or not.
Regards
Marcel
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2019-07-25 9:39 ` Marcel Holtmann
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