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Message-ID: <aa095579-84d3-4157-91fc-23613ae30448@molgen.mpg.de>
Date: Tue, 6 May 2025 10:46:13 +0200
From: Paul Menzel <pmenzel@...gen.mpg.de>
To: En-Wei Wu <en-wei.wu@...onical.com>
Cc: marcel@...tmann.org, luiz.dentz@...il.com,
linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org,
quic_tjiang@...cinc.com
Subject: Re: [PATCH] Bluetooth: btusb: use skb_pull to avoid unsafe access in
QCA dump handling
Dear En-Wei,
Thank you for your patch.
Am 06.05.25 um 04:48 schrieb En-Wei Wu:
> Use skb_pull() and skb_pull_data() to safely parse QCA dump packets.
>
> This avoids direct pointer math on skb->data, which could lead to
> invalid access if the packet is shorter than expected.
Please add a Fixes: tag.
Also, how did you test this?
> Signed-off-by: En-Wei Wu <en-wei.wu@...onical.com>
> ---
> drivers/bluetooth/btusb.c | 99 ++++++++++++++++-----------------------
> 1 file changed, 41 insertions(+), 58 deletions(-)
>
> diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
> index 357b18dae8de..17136924a278 100644
> --- a/drivers/bluetooth/btusb.c
> +++ b/drivers/bluetooth/btusb.c
> @@ -2979,9 +2979,8 @@ static void btusb_coredump_qca(struct hci_dev *hdev)
> static int handle_dump_pkt_qca(struct hci_dev *hdev, struct sk_buff *skb)
> {
> int ret = 0;
> + int skip = 0;
`unsigned int`, as the signature is:
include/linux/skbuff.h:void *skb_pull(struct sk_buff *skb, unsigned
int len);
> u8 pkt_type;
> - u8 *sk_ptr;
> - unsigned int sk_len;
> u16 seqno;
> u32 dump_size;
>
> @@ -2990,18 +2989,14 @@ static int handle_dump_pkt_qca(struct hci_dev *hdev, struct sk_buff *skb)
> struct usb_device *udev = btdata->udev;
>
> pkt_type = hci_skb_pkt_type(skb);
> - sk_ptr = skb->data;
> - sk_len = skb->len;
> -
> - if (pkt_type == HCI_ACLDATA_PKT) {
> - sk_ptr += HCI_ACL_HDR_SIZE;
> - sk_len -= HCI_ACL_HDR_SIZE;
> - }
> + if (pkt_type == HCI_ACLDATA_PKT)
> + skip = sizeof(struct hci_acl_hdr) + sizeof(struct hci_event_hdr);
> + else
> + skip = sizeof(struct hci_event_hdr);
Maybe write it as below:
skip = sizeof(struct hci_event_hdr);
if (pkt_type == HCI_ACLDATA_PKT)
skip += sizeof(struct hci_acl_hdr);
Kind regards,
Paul
>
> - sk_ptr += HCI_EVENT_HDR_SIZE;
> - sk_len -= HCI_EVENT_HDR_SIZE;
> + skb_pull(skb, skip);
> + dump_hdr = (struct qca_dump_hdr *)skb->data;
>
> - dump_hdr = (struct qca_dump_hdr *)sk_ptr;
> seqno = le16_to_cpu(dump_hdr->seqno);
> if (seqno == 0) {
> set_bit(BTUSB_HW_SSR_ACTIVE, &btdata->flags);
> @@ -3021,16 +3016,15 @@ static int handle_dump_pkt_qca(struct hci_dev *hdev, struct sk_buff *skb)
>
> btdata->qca_dump.ram_dump_size = dump_size;
> btdata->qca_dump.ram_dump_seqno = 0;
> - sk_ptr += offsetof(struct qca_dump_hdr, data0);
> - sk_len -= offsetof(struct qca_dump_hdr, data0);
> +
> + skb_pull(skb, offsetof(struct qca_dump_hdr, data0));
>
> usb_disable_autosuspend(udev);
> bt_dev_info(hdev, "%s memdump size(%u)\n",
> (pkt_type == HCI_ACLDATA_PKT) ? "ACL" : "event",
> dump_size);
> } else {
> - sk_ptr += offsetof(struct qca_dump_hdr, data);
> - sk_len -= offsetof(struct qca_dump_hdr, data);
> + skb_pull(skb, offsetof(struct qca_dump_hdr, data));
> }
>
> if (!btdata->qca_dump.ram_dump_size) {
> @@ -3050,7 +3044,6 @@ static int handle_dump_pkt_qca(struct hci_dev *hdev, struct sk_buff *skb)
> return ret;
> }
>
> - skb_pull(skb, skb->len - sk_len);
> hci_devcd_append(hdev, skb);
> btdata->qca_dump.ram_dump_seqno++;
> if (seqno == QCA_LAST_SEQUENCE_NUM) {
> @@ -3078,68 +3071,58 @@ static int handle_dump_pkt_qca(struct hci_dev *hdev, struct sk_buff *skb)
> /* Return: true if the ACL packet is a dump packet, false otherwise. */
> static bool acl_pkt_is_dump_qca(struct hci_dev *hdev, struct sk_buff *skb)
> {
> - u8 *sk_ptr;
> - unsigned int sk_len;
> -
> struct hci_event_hdr *event_hdr;
> struct hci_acl_hdr *acl_hdr;
> struct qca_dump_hdr *dump_hdr;
> + struct sk_buff *clone = skb_clone(skb, GFP_ATOMIC);
> + bool is_dump = false;
>
> - sk_ptr = skb->data;
> - sk_len = skb->len;
> -
> - acl_hdr = hci_acl_hdr(skb);
> - if (le16_to_cpu(acl_hdr->handle) != QCA_MEMDUMP_ACL_HANDLE)
> + if (!clone)
> return false;
>
> - sk_ptr += HCI_ACL_HDR_SIZE;
> - sk_len -= HCI_ACL_HDR_SIZE;
> - event_hdr = (struct hci_event_hdr *)sk_ptr;
> -
> - if ((event_hdr->evt != HCI_VENDOR_PKT) ||
> - (event_hdr->plen != (sk_len - HCI_EVENT_HDR_SIZE)))
> - return false;
> + acl_hdr = skb_pull_data(clone, sizeof(*acl_hdr));
> + if (!acl_hdr || (le16_to_cpu(acl_hdr->handle) != QCA_MEMDUMP_ACL_HANDLE))
> + goto out;
>
> - sk_ptr += HCI_EVENT_HDR_SIZE;
> - sk_len -= HCI_EVENT_HDR_SIZE;
> + event_hdr = skb_pull_data(clone, sizeof(*event_hdr));
> + if (!event_hdr || (event_hdr->evt != HCI_VENDOR_PKT))
> + goto out;
>
> - dump_hdr = (struct qca_dump_hdr *)sk_ptr;
> - if ((sk_len < offsetof(struct qca_dump_hdr, data)) ||
> - (dump_hdr->vse_class != QCA_MEMDUMP_VSE_CLASS) ||
> - (dump_hdr->msg_type != QCA_MEMDUMP_MSG_TYPE))
> - return false;
> + dump_hdr = skb_pull_data(clone, sizeof(*dump_hdr));
> + if (!dump_hdr || (dump_hdr->vse_class != QCA_MEMDUMP_VSE_CLASS) ||
> + (dump_hdr->msg_type != QCA_MEMDUMP_MSG_TYPE))
> + goto out;
>
> - return true;
> + is_dump = true;
> +out:
> + consume_skb(clone);
> + return is_dump;
> }
>
> /* Return: true if the event packet is a dump packet, false otherwise. */
> static bool evt_pkt_is_dump_qca(struct hci_dev *hdev, struct sk_buff *skb)
> {
> - u8 *sk_ptr;
> - unsigned int sk_len;
> -
> struct hci_event_hdr *event_hdr;
> struct qca_dump_hdr *dump_hdr;
> + struct sk_buff *clone = skb_clone(skb, GFP_ATOMIC);
> + bool is_dump = false;
>
> - sk_ptr = skb->data;
> - sk_len = skb->len;
> -
> - event_hdr = hci_event_hdr(skb);
> -
> - if ((event_hdr->evt != HCI_VENDOR_PKT)
> - || (event_hdr->plen != (sk_len - HCI_EVENT_HDR_SIZE)))
> + if (!clone)
> return false;
>
> - sk_ptr += HCI_EVENT_HDR_SIZE;
> - sk_len -= HCI_EVENT_HDR_SIZE;
> + event_hdr = skb_pull_data(clone, sizeof(*event_hdr));
> + if (!event_hdr || (event_hdr->evt != HCI_VENDOR_PKT))
> + goto out;
>
> - dump_hdr = (struct qca_dump_hdr *)sk_ptr;
> - if ((sk_len < offsetof(struct qca_dump_hdr, data)) ||
> - (dump_hdr->vse_class != QCA_MEMDUMP_VSE_CLASS) ||
> - (dump_hdr->msg_type != QCA_MEMDUMP_MSG_TYPE))
> - return false;
> + dump_hdr = skb_pull_data(clone, sizeof(*dump_hdr));
> + if (!dump_hdr || (dump_hdr->vse_class != QCA_MEMDUMP_VSE_CLASS) ||
> + (dump_hdr->msg_type != QCA_MEMDUMP_MSG_TYPE))
> + goto out;
>
> - return true;
> + is_dump = true;
> +out:
> + consume_skb(clone);
> + return is_dump;
> }
>
> static int btusb_recv_acl_qca(struct hci_dev *hdev, struct sk_buff *skb)
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