linux-kernel - Re: [PATCH net] Bluetooth: MGMT: Fix OOB access in parse_adv_monitor

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Message-ID: <CABBYNZKUNecJNPmrVFdkkOhG1A8C_32pUOdh0ZDWkCNkAugDdQ@mail.gmail.com>
Date: Thu, 23 Oct 2025 09:18:13 -0400
From: Luiz Augusto von Dentz <luiz.dentz@...il.com>
To: Ilia Gavrilov <Ilia.Gavrilov@...otecs.ru>
Cc: Marcel Holtmann <marcel@...tmann.org>, Johan Hedberg <johan.hedberg@...il.com>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	"linux-bluetooth@...r.kernel.org" <linux-bluetooth@...r.kernel.org>, 
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"lvc-project@...uxtesting.org" <lvc-project@...uxtesting.org>, 
	"stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH net] Bluetooth: MGMT: Fix OOB access in parse_adv_monitor_pattern()

Hi Ilia,

On Mon, Oct 20, 2025 at 11:12 AM Ilia Gavrilov
<Ilia.Gavrilov@...otecs.ru> wrote:
>
> In the parse_adv_monitor_pattern() function, the value of
> the 'length' variable is currently limited to HCI_MAX_EXT_AD_LENGTH(251).
> The size of the 'value' array in the mgmt_adv_pattern structure is 31.
> If the value of 'pattern[i].length' is set in the user space
> and exceeds 31, the 'patterns[i].value' array can be accessed
> out of bound when copied.
>
> Increasing the size of the 'value' array in
> the 'mgmt_adv_pattern' structure will break the userspace.
> Considering this, and to avoid OOB access revert the limits for 'offset'
> and 'length' back to the value of HCI_MAX_AD_LENGTH.
>
> Found by InfoTeCS on behalf of Linux Verification Center
> (linuxtesting.org) with SVACE.
>
> Fixes: db08722fc7d4 ("Bluetooth: hci_core: Fix missing instances using HCI_MAX_AD_LENGTH")
> Cc: stable@...r.kernel.org
> Signed-off-by: Ilia Gavrilov <Ilia.Gavrilov@...otecs.ru>
> ---
>  include/net/bluetooth/mgmt.h | 2 +-
>  net/bluetooth/mgmt.c         | 6 +++---
>  2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/include/net/bluetooth/mgmt.h b/include/net/bluetooth/mgmt.h
> index 74edea06985b..4b07ce6dfd69 100644
> --- a/include/net/bluetooth/mgmt.h
> +++ b/include/net/bluetooth/mgmt.h
> @@ -780,7 +780,7 @@ struct mgmt_adv_pattern {
>         __u8 ad_type;
>         __u8 offset;
>         __u8 length;
> -       __u8 value[31];
> +       __u8 value[HCI_MAX_AD_LENGTH];

Why not use HCI_MAX_EXT_AD_LENGTH above? Or perhaps even make it
opaque since the actual size is defined by length - offset.

>  } __packed;
>
>  #define MGMT_OP_ADD_ADV_PATTERNS_MONITOR       0x0052
> diff --git a/net/bluetooth/mgmt.c b/net/bluetooth/mgmt.c
> index a3d16eece0d2..500033b70a96 100644
> --- a/net/bluetooth/mgmt.c
> +++ b/net/bluetooth/mgmt.c
> @@ -5391,9 +5391,9 @@ static u8 parse_adv_monitor_pattern(struct adv_monitor *m, u8 pattern_count,
>         for (i = 0; i < pattern_count; i++) {
>                 offset = patterns[i].offset;
>                 length = patterns[i].length;
> -               if (offset >= HCI_MAX_EXT_AD_LENGTH ||
> -                   length > HCI_MAX_EXT_AD_LENGTH ||
> -                   (offset + length) > HCI_MAX_EXT_AD_LENGTH)
> +               if (offset >= HCI_MAX_AD_LENGTH ||
> +                   length > HCI_MAX_AD_LENGTH ||
> +                   (offset + length) > HCI_MAX_AD_LENGTH)
>                         return MGMT_STATUS_INVALID_PARAMS;
>
>                 p = kmalloc(sizeof(*p), GFP_KERNEL);
> --
> 2.39.5



-- 
Luiz Augusto von Dentz