Re: Re: Re: [PATCH v3] Bluetooth: HIDP: add missing length check for incoming frames

[Muhammad Bilal]

Hi Jiale,

Looks correct. Both goto failed paths free the skb properly now, and
the intr_frame goto also avoids a NULL hdr deref.

Reviewed-by: Muhammad Bilal <meatuni001@xxxxxxxxx>

Thanks,
Muhammad Bilal

On Tue, Jul 21, 2026 at 10:55 AM jiale yao <19888972804@xxxxxxx> wrote:
>
> In hidp_recv_ctrl_frame() and hidp_recv_intr_frame(), skb->data[0] is
> read without verifying that skb->len >= 1.  A zero-length L2CAP PDU
> delivered via the HIDP control or interrupt channel causes an
> out-of-bounds read.
>
> Use skb_pull_data(skb, 1) which combines the length check and pull
> in one operation, matching the existing pattern in hidp_input_report()
> and the fix in commit 6770d3a8acdf ("Bluetooth: bnep: reject short
> frames before parsing") which addressed the same class of bug in BNEP.
>
> Assisted-by: Claude:deepseek-v4-pro
> Signed-off-by: Jiale Yao <yaojiale02@xxxxxxx>
> ---
>  net/bluetooth/hidp/core.c | 25 +++++++++++++++----------
>  1 file changed, 15 insertions(+), 10 deletions(-)
>
> diff --git a/net/bluetooth/hidp/core.c b/net/bluetooth/hidp/core.c
> index 0e24c5e2955e..e29fe66f01d4 100644
> --- a/net/bluetooth/hidp/core.c
> +++ b/net/bluetooth/hidp/core.c
> @@ -560,16 +560,18 @@ static int hidp_process_data(struct hidp_session *session, struct sk_buff *skb,
>  static void hidp_recv_ctrl_frame(struct hidp_session *session,
>                                         struct sk_buff *skb)
>  {
> -       unsigned char hdr, type, param;
> +       unsigned char *hdr;
> +       unsigned char type, param;
>         int free_skb = 1;
>
>         BT_DBG("session %p skb %p len %u", session, skb, skb->len);
>
> -       hdr = skb->data[0];
> -       skb_pull(skb, 1);
> +       hdr = skb_pull_data(skb, 1);
> +       if (!hdr)
> +               goto failed;
>
> -       type = hdr & HIDP_HEADER_TRANS_MASK;
> -       param = hdr & HIDP_HEADER_PARAM_MASK;
> +       type = *hdr & HIDP_HEADER_TRANS_MASK;
> +       param = *hdr & HIDP_HEADER_PARAM_MASK;
>
>         switch (type) {
>         case HIDP_TRANS_HANDSHAKE:
> @@ -590,6 +592,7 @@ static void hidp_recv_ctrl_frame(struct hidp_session *session,
>                 break;
>         }
>
> +failed:
>         if (free_skb)
>                 kfree_skb(skb);
>  }
> @@ -597,14 +600,15 @@ static void hidp_recv_ctrl_frame(struct hidp_session *session,
>  static void hidp_recv_intr_frame(struct hidp_session *session,
>                                 struct sk_buff *skb)
>  {
> -       unsigned char hdr;
> +       unsigned char *hdr;
>
>         BT_DBG("session %p skb %p len %u", session, skb, skb->len);
>
> -       hdr = skb->data[0];
> -       skb_pull(skb, 1);
> +       hdr = skb_pull_data(skb, 1);
> +       if (!hdr)
> +               goto failed;
>
> -       if (hdr == (HIDP_TRANS_DATA | HIDP_DATA_RTYPE_INPUT)) {
> +       if (*hdr == (HIDP_TRANS_DATA | HIDP_DATA_RTYPE_INPUT)) {
>                 hidp_set_timer(session);
>
>                 if (session->input)
> @@ -616,9 +620,10 @@ static void hidp_recv_intr_frame(struct hidp_session *session,
>                         BT_DBG("report len %d", skb->len);
>                 }
>         } else {
> -               BT_DBG("Unsupported protocol header 0x%02x", hdr);
> +               BT_DBG("Unsupported protocol header 0x%02x", *hdr);
>         }
>
> +failed:
>         kfree_skb(skb);
>  }
>
> --
> 2.34.1
>
>
>
>
>
>
>
> At 2026-07-21 03:47:21, "Luiz Augusto von Dentz" <luiz.dentz@xxxxxxxxx> wrote:
> >Hi,
> >
> >On Sun, Jul 19, 2026 at 1:38 AM jiale yao <19888972804@xxxxxxx> wrote:
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >> In hidp_recv_ctrl_frame() and hidp_recv_intr_frame(), skb->data[0] is
> >> read without verifying that skb->len >= 1.  A zero-length L2CAP PDU
> >> delivered via the HIDP control or interrupt channel causes an
> >> out-of-bounds read.
> >>
> >> Use skb_pull_data(skb, 1) which combines the length check and pull
> >> in one operation, matching the existing pattern in hidp_input_report()
> >> and the fix in commit 6770d3a8acdf ("Bluetooth: bnep: reject short
> >> frames before parsing") which addressed the same class of bug in BNEP.
> >>
> >> Assisted-by: Claude:deepseek-v4-pro
> >> Signed-off-by: Jiale Yao <yaojiale02@xxxxxxx>
> >> ---
> >>  net/bluetooth/hidp/core.c | 21 ++++++++++++---------
> >>  1 file changed, 12 insertions(+), 9 deletions(-)
> >>
> >> diff --git a/net/bluetooth/hidp/core.c b/net/bluetooth/hidp/core.c
> >> index 0e24c5e2955e..bb61602b02e1 100644
> >> --- a/net/bluetooth/hidp/core.c
> >> +++ b/net/bluetooth/hidp/core.c
> >> @@ -560,16 +560,18 @@ static int hidp_process_data(struct hidp_session *session, struct sk_buff *skb,
> >>  static void hidp_recv_ctrl_frame(struct hidp_session *session,
> >>                                         struct sk_buff *skb)
> >>  {
> >> -       unsigned char hdr, type, param;
> >> +       unsigned char *hdr;
> >> +       unsigned char type, param;
> >>         int free_skb = 1;
> >>
> >>         BT_DBG("session %p skb %p len %u", session, skb, skb->len);
> >>
> >> -       hdr = skb->data[0];
> >> -       skb_pull(skb, 1);
> >> +       hdr = skb_pull_data(skb, 1);
> >> +       if (!hdr)
> >> +               return;
> >
> >https://sashiko.dev/#/patchset/20260717153238.2002330-1-yaojiale02%40163.com
> >
> >It seems that by early returning we are leaking the skb.
> >
> >>
> >> -       type = hdr & HIDP_HEADER_TRANS_MASK;
> >> -       param = hdr & HIDP_HEADER_PARAM_MASK;
> >> +       type = *hdr & HIDP_HEADER_TRANS_MASK;
> >> +       param = *hdr & HIDP_HEADER_PARAM_MASK;
> >>
> >>         switch (type) {
> >>         case HIDP_TRANS_HANDSHAKE:
> >> @@ -597,14 +599,15 @@ static void hidp_recv_ctrl_frame(struct hidp_session *session,
> >>  static void hidp_recv_intr_frame(struct hidp_session *session,
> >>                                 struct sk_buff *skb)
> >>  {
> >> -       unsigned char hdr;
> >> +       unsigned char *hdr;
> >>
> >>         BT_DBG("session %p skb %p len %u", session, skb, skb->len);
> >>
> >> -       hdr = skb->data[0];
> >> -       skb_pull(skb, 1);
> >> +       hdr = skb_pull_data(skb, 1);
> >> +       if (!hdr)
> >> +               return;
> >>
> >> -       if (hdr == (HIDP_TRANS_DATA | HIDP_DATA_RTYPE_INPUT)) {
> >> +       if (*hdr == (HIDP_TRANS_DATA | HIDP_DATA_RTYPE_INPUT)) {
> >>                 hidp_set_timer(session);
> >>
> >>                 if (session->input)
> >> --
> >> 2.34.1
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >> At 2026-07-17 23:40:11, "Luiz Augusto von Dentz" <luiz.dentz@xxxxxxxxx> wrote:
> >> >Hi,
> >> >
> >> >On Fri, Jul 17, 2026 at 11:33 AM Jiale Yao <yaojiale02@xxxxxxx> wrote:
> >> >>
> >> >> In hidp_recv_ctrl_frame() and hidp_recv_intr_frame(), skb->data[0] is
> >> >> read without verifying that skb->len >= 1.  A zero-length L2CAP PDU
> >> >> delivered via the HIDP control or interrupt channel causes an
> >> >> out-of-bounds read.
> >> >>
> >> >> Add pskb_may_pull(skb, 1) guards before both reads, matching the fix
> >> >> in commit 6770d3a8acdf ("Bluetooth: bnep: reject short frames before
> >> >> parsing") which addressed the same class of bug in BNEP.
> >> >>
> >> >> Assisted-by: Claude:deepseek-v4-pro
> >> >> Signed-off-by: Jiale Yao <yaojiale02@xxxxxxx>
> >> >> ---
> >> >>  net/bluetooth/hidp/core.c | 4 ++++
> >> >>  1 file changed, 4 insertions(+)
> >> >>
> >> >> diff --git a/net/bluetooth/hidp/core.c b/net/bluetooth/hidp/core.c
> >> >> index 0e24c5e2955e..6c7da8aca732 100644
> >> >> --- a/net/bluetooth/hidp/core.c
> >> >> +++ b/net/bluetooth/hidp/core.c
> >> >> @@ -565,6 +565,8 @@ static void hidp_recv_ctrl_frame(struct hidp_session *session,
> >> >>
> >> >>         BT_DBG("session %p skb %p len %u", session, skb, skb->len);
> >> >>
> >> >> +       if (!pskb_may_pull(skb, 1))
> >> >> +               return;
> >> >
> >> >We can probably replace this with skb_pull_data.
> >> >
> >> >>         hdr = skb->data[0];
> >> >>         skb_pull(skb, 1);
> >> >>
> >> >> @@ -601,6 +603,8 @@ static void hidp_recv_intr_frame(struct hidp_session *session,
> >> >>
> >> >>         BT_DBG("session %p skb %p len %u", session, skb, skb->len);
> >> >>
> >> >> +       if (!pskb_may_pull(skb, 1))
> >> >> +               return;
> >> >
> >> >Ditto.
> >> >
> >> >>         hdr = skb->data[0];
> >> >>         skb_pull(skb, 1);
> >> >>
> >> >> --
> >> >> 2.34.1
> >> >>
> >> >
> >> >
> >> >--
> >> >Luiz Augusto von Dentz
> >
> >
> >
> >--
> >Luiz Augusto von Dentz