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Subject[PATCH] Bluetooth: btusb: fix excessive stack usage
Date
From: Arnd Bergmann <arnd@arndb.de>

Enlarging the size of 'struct btmtk_hci_wmt_cmd' makes it no longer
fit on the kernel stack, as seen from this compiler warning:

drivers/bluetooth/btusb.c:3365:12: error: stack frame size of 1036 bytes in function 'btusb_mtk_hci_wmt_sync' [-Werror,-Wframe-larger-than=]

Change the function to dynamically allocate the buffer instead.
As there are other sleeping functions called from the same location,
using GFP_KERNEL should be fine here, and the runtime overhead should
not matter as this is rarely called.

Unfortunately, I could not figure out why the message size is
increased in the previous patch. Using dynamic allocation means
any size is possible now, but there is still a range check that
limits the total size (including the five-byte header) to 255
bytes, so whatever was intended there is now undone.

Fixes: 48c13301e6ba ("Bluetooth: btusb: Fine-tune mt7663 mechanism.")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
drivers/bluetooth/btusb.c | 24 +++++++++++++++---------
1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
index eeafb8432c0f..838e6682301e 100644
--- a/drivers/bluetooth/btusb.c
+++ b/drivers/bluetooth/btusb.c
@@ -3161,7 +3161,7 @@ struct btmtk_wmt_hdr {

struct btmtk_hci_wmt_cmd {
struct btmtk_wmt_hdr hdr;
- u8 data[1000];
+ u8 data[];
} __packed;

struct btmtk_hci_wmt_evt {
@@ -3369,7 +3369,7 @@ static int btusb_mtk_hci_wmt_sync(struct hci_dev *hdev,
struct btmtk_hci_wmt_evt_funcc *wmt_evt_funcc;
u32 hlen, status = BTMTK_WMT_INVALID;
struct btmtk_hci_wmt_evt *wmt_evt;
- struct btmtk_hci_wmt_cmd wc;
+ struct btmtk_hci_wmt_cmd *wc;
struct btmtk_wmt_hdr *hdr;
int err;

@@ -3383,20 +3383,24 @@ static int btusb_mtk_hci_wmt_sync(struct hci_dev *hdev,
if (hlen > 255)
return -EINVAL;

- hdr = (struct btmtk_wmt_hdr *)&wc;
+ wc = kzalloc(hlen, GFP_KERNEL);
+ if (!wc)
+ return -ENOMEM;
+
+ hdr = &wc->hdr;
hdr->dir = 1;
hdr->op = wmt_params->op;
hdr->dlen = cpu_to_le16(wmt_params->dlen + 1);
hdr->flag = wmt_params->flag;
- memcpy(wc.data, wmt_params->data, wmt_params->dlen);
+ memcpy(wc->data, wmt_params->data, wmt_params->dlen);

set_bit(BTUSB_TX_WAIT_VND_EVT, &data->flags);

- err = __hci_cmd_send(hdev, 0xfc6f, hlen, &wc);
+ err = __hci_cmd_send(hdev, 0xfc6f, hlen, wc);

if (err < 0) {
clear_bit(BTUSB_TX_WAIT_VND_EVT, &data->flags);
- return err;
+ goto err_free_wc;
}

/* The vendor specific WMT commands are all answered by a vendor
@@ -3413,13 +3417,14 @@ static int btusb_mtk_hci_wmt_sync(struct hci_dev *hdev,
if (err == -EINTR) {
bt_dev_err(hdev, "Execution of wmt command interrupted");
clear_bit(BTUSB_TX_WAIT_VND_EVT, &data->flags);
- return err;
+ goto err_free_wc;
}

if (err) {
bt_dev_err(hdev, "Execution of wmt command timed out");
clear_bit(BTUSB_TX_WAIT_VND_EVT, &data->flags);
- return -ETIMEDOUT;
+ err = -ETIMEDOUT;
+ goto err_free_wc;
}

/* Parse and handle the return WMT event */
@@ -3463,7 +3468,8 @@ static int btusb_mtk_hci_wmt_sync(struct hci_dev *hdev,
err_free_skb:
kfree_skb(data->evt_skb);
data->evt_skb = NULL;
-
+err_free_wc:
+ kfree(wc);
return err;
}

--
2.29.2
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