linux-kernel - Re: [PATCH] Bluetooth: Fix a buffer overflow in mgmt_mesh

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Date:   Wed, 14 Dec 2022 01:00:11 +0000
From:   "Gix, Brian" <brian.gix@...el.com>
To:     "harshit.m.mogalapalli@...cle.com" <harshit.m.mogalapalli@...cle.com>
CC:     "darren.kenny@...cle.com" <darren.kenny@...cle.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "luiz.dentz@...il.com" <luiz.dentz@...il.com>,
        "marcel@...tmann.org" <marcel@...tmann.org>,
        "harshit.m.mogalapalli@...il.com" <harshit.m.mogalapalli@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "johan.hedberg@...il.com" <johan.hedberg@...il.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "error27@...il.com" <error27@...il.com>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "linux-bluetooth@...r.kernel.org" <linux-bluetooth@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH] Bluetooth: Fix a buffer overflow in mgmt_mesh_add()

Signed-off: brian.gix@...el.com

On Mon, 2022-12-12 at 05:08 -0800, Harshit Mogalapalli wrote:
> Smatch Warning:
> net/bluetooth/mgmt_util.c:375 mgmt_mesh_add() error: __memcpy()
> 'mesh_tx->param' too small (48 vs 50)
> 
> Analysis:
> 
> 'mesh_tx->param' is array of size 48. This is the destination.
> u8 param[sizeof(struct mgmt_cp_mesh_send) + 29]; // 19 + 29 = 48.
> 
> But in the caller 'mesh_send' we reject only when len > 50.
> len > (MGMT_MESH_SEND_SIZE + 31) // 19 + 31 = 50.
> 
> Fixes: b338d91703fa ("Bluetooth: Implement support for Mesh")
> Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
> ---
> This is based on static analysis, I am unsure if we should put
> an upper bound to len(48) instead.
> 
> This limit on length changed between v4 and v5 patches of Commit:
> ("Bluetooth: Implement support for Mesh") in function mesh_send()
> 
> v4:
> https://lore.kernel.org/all/20220511155412.740249-2-brian.gix@intel.com/
> v5:
> https://lore.kernel.org/all/20220720194511.320773-2-brian.gix@intel.com/
> ---
>  net/bluetooth/mgmt_util.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/bluetooth/mgmt_util.h b/net/bluetooth/mgmt_util.h
> index 6a8b7e84293d..bdf978605d5a 100644
> --- a/net/bluetooth/mgmt_util.h
> +++ b/net/bluetooth/mgmt_util.h
> @@ -27,7 +27,7 @@ struct mgmt_mesh_tx {
>         struct sock *sk;
>         u8 handle;
>         u8 instance;
> -       u8 param[sizeof(struct mgmt_cp_mesh_send) + 29];
> +       u8 param[sizeof(struct mgmt_cp_mesh_send) + 31];
>  };
>  
>  struct mgmt_pending_cmd {