linux-kernel - Re: [PATCH] Bluetooth: hci: fix null-ptr-deref in hci_read_supported

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Message-ID: <CABBYNZJBmbjB6ZwT7JogaABE3d0-vWwNQq4NwUGCHsmgNuKXLA@mail.gmail.com>
Date: Wed, 3 Jul 2024 10:25:27 -0400
From: Luiz Augusto von Dentz <luiz.dentz@...il.com>
To: Sungwoo Kim <iam@...g-woo.kim>
Cc: daveti@...due.edu, benquike@...il.com, 
	Marcel Holtmann <marcel@...tmann.org>, Johan Hedberg <johan.hedberg@...il.com>, 
	linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Bluetooth: hci: fix null-ptr-deref in hci_read_supported_codecs

Hi,

On Wed, Jul 3, 2024 at 7:40 AM Sungwoo Kim <iam@...g-woo.kim> wrote:
>
> KASAN: null-ptr-deref in range [0x0000000000000070-0x0000000000000077]
> CPU: 1 PID: 2000 Comm: kworker/u9:5 Not tainted 6.9.0-ga6bcb805883c-dirty #10
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
> Workqueue: hci7 hci_power_on
> RIP: 0010:hci_read_supported_codecs+0xb9/0x870 net/bluetooth/hci_codec.c:138
> Code: 08 48 89 ef e8 b8 c1 8f fd 48 8b 75 00 e9 96 00 00 00 49 89 c6 48 ba 00 00 00 00 00 fc ff df 4c 8d 60 70 4c 89 e3 48 c1 eb 03 <0f> b6 04 13 84 c0 0f 85 82 06 00 00 41 83 3c 24 02 77 0a e8 bf 78
> RSP: 0018:ffff888120bafac8 EFLAGS: 00010212
> RAX: 0000000000000000 RBX: 000000000000000e RCX: ffff8881173f0040
> RDX: dffffc0000000000 RSI: ffffffffa58496c0 RDI: ffff88810b9ad1e4
> RBP: ffff88810b9ac000 R08: ffffffffa77882a7 R09: 1ffffffff4ef1054
> R10: dffffc0000000000 R11: fffffbfff4ef1055 R12: 0000000000000070
> R13: 0000000000000000 R14: 0000000000000000 R15: ffff88810b9ac000
> FS:  0000000000000000(0000) GS:ffff8881f6c00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f6ddaa3439e CR3: 0000000139764003 CR4: 0000000000770ef0
> PKRU: 55555554
> Call Trace:
>  <TASK>
>  hci_read_local_codecs_sync net/bluetooth/hci_sync.c:4546 [inline]
>  hci_init_stage_sync net/bluetooth/hci_sync.c:3441 [inline]
>  hci_init4_sync net/bluetooth/hci_sync.c:4706 [inline]
>  hci_init_sync net/bluetooth/hci_sync.c:4742 [inline]
>  hci_dev_init_sync net/bluetooth/hci_sync.c:4912 [inline]
>  hci_dev_open_sync+0x19a9/0x2d30 net/bluetooth/hci_sync.c:4994
>  hci_dev_do_open net/bluetooth/hci_core.c:483 [inline]
>  hci_power_on+0x11e/0x560 net/bluetooth/hci_core.c:1015
>  process_one_work kernel/workqueue.c:3267 [inline]
>  process_scheduled_works+0x8ef/0x14f0 kernel/workqueue.c:3348
>  worker_thread+0x91f/0xe50 kernel/workqueue.c:3429
>  kthread+0x2cb/0x360 kernel/kthread.c:388
>  ret_from_fork+0x4d/0x80 arch/x86/kernel/process.c:147
>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
>
> Fixes: 8961987f3f5f ("Bluetooth: Enumerate local supported codec and cache details")
> Fixes: 9ae664028a9e ("Bluetooth: Add support for Read Local Supported Codecs V2")
>
> Signed-off-by: Sungwoo Kim <iam@...g-woo.kim>
> ---
>  net/bluetooth/hci_codec.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/net/bluetooth/hci_codec.c b/net/bluetooth/hci_codec.c
> index 3cc135bb1..5c98eec2c 100644
> --- a/net/bluetooth/hci_codec.c
> +++ b/net/bluetooth/hci_codec.c
> @@ -74,6 +74,9 @@ static void hci_read_codec_capabilities(struct hci_dev *hdev, __u8 transport,
>
>                         skb = __hci_cmd_sync_sk(hdev, HCI_OP_READ_LOCAL_CODEC_CAPS,
>                                                 sizeof(*cmd), cmd, 0, HCI_CMD_TIMEOUT, NULL);
> +
> +                       if (!skb)
> +                               skb = ERR_PTR(-EINVAL);
>                         if (IS_ERR(skb)) {
>                                 bt_dev_err(hdev, "Failed to read codec capabilities (%ld)",
>                                            PTR_ERR(skb));
> @@ -129,6 +132,8 @@ void hci_read_supported_codecs(struct hci_dev *hdev)
>         skb = __hci_cmd_sync_sk(hdev, HCI_OP_READ_LOCAL_CODECS, 0, NULL,
>                                 0, HCI_CMD_TIMEOUT, NULL);
>
> +       if (!skb)
> +               skb = ERR_PTR(-EINVAL);
>         if (IS_ERR(skb)) {
>                 bt_dev_err(hdev, "Failed to read local supported codecs (%ld)",
>                            PTR_ERR(skb));
> @@ -198,6 +203,8 @@ void hci_read_supported_codecs_v2(struct hci_dev *hdev)
>         skb = __hci_cmd_sync_sk(hdev, HCI_OP_READ_LOCAL_CODECS_V2, 0, NULL,
>                                 0, HCI_CMD_TIMEOUT, NULL);
>
> +       if (!skb)
> +               skb = ERR_PTR(-EINVAL);
>         if (IS_ERR(skb)) {
>                 bt_dev_err(hdev, "Failed to read local supported codecs (%ld)",
>                            PTR_ERR(skb));
> --
> 2.34.1


There is something that doesn't quite add here, we don't return NULL
on __hci_cmd_sync_sk, if there is an error it will always return
ERR_PTR or perhaps this is the result of rsp_skb being NULL in which
case we shall check it and actually return ERR_PTR directly from
__hci_cmd_sync_sk but Id like to understand under what circumstances
does rsp_skb can be NULL.


-- 
Luiz Augusto von Dentz