netdev - Re: [PATCH] Bluetooth: sco: Fix crash when using BT_SNDMTU/BT

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Date:   Mon, 16 Nov 2020 16:00:59 -0800
From:   Luiz Augusto von Dentz <luiz.dentz@...il.com>
To:     Wei Yongjun <weiyongjun1@...wei.com>
Cc:     "linux-bluetooth@...r.kernel.org" <linux-bluetooth@...r.kernel.org>,
        "open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>,
        Hulk Robot <hulkci@...wei.com>
Subject: Re: [PATCH] Bluetooth: sco: Fix crash when using BT_SNDMTU/BT_RCVMTU option

Hi,

On Mon, Nov 16, 2020 at 5:22 AM Wei Yongjun <weiyongjun1@...wei.com> wrote:
>
> This commit add the invalid check for connected socket, without it will
> causes the following crash due to sco_pi(sk)->conn being NULL:
>
> KASAN: null-ptr-deref in range [0x0000000000000050-0x0000000000000057]
> CPU: 3 PID: 4284 Comm: test_sco Not tainted 5.10.0-rc3+ #1
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1 04/01/2014
> RIP: 0010:sco_sock_getsockopt+0x45d/0x8e0
> Code: 48 c1 ea 03 80 3c 02 00 0f 85 ca 03 00 00 49 8b 9d f8 04 00 00 48 b8 00
>       00 00 00 00 fc ff df 48 8d 7b 50 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84
>       c0 74 08 3c 03 0f 8e b5 03 00 00 8b 43 50 48 8b 0c
> RSP: 0018:ffff88801bb17d88 EFLAGS: 00010206
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff83a4ecdf
> RDX: 000000000000000a RSI: ffffc90002fce000 RDI: 0000000000000050
> RBP: 1ffff11003762fb4 R08: 0000000000000001 R09: ffff88810e1008c0
> R10: ffffffffbd695dcf R11: fffffbfff7ad2bb9 R12: 0000000000000000
> R13: ffff888018ff1000 R14: dffffc0000000000 R15: 000000000000000d
> FS:  00007fb4f76c1700(0000) GS:ffff88811af80000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00005555e3b7a938 CR3: 00000001117be001 CR4: 0000000000770ee0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> PKRU: 55555554
> Call Trace:
>  ? sco_skb_put_cmsg+0x80/0x80
>  ? sco_skb_put_cmsg+0x80/0x80
>  __sys_getsockopt+0x12a/0x220
>  ? __ia32_sys_setsockopt+0x150/0x150
>  ? syscall_enter_from_user_mode+0x18/0x50
>  ? rcu_read_lock_bh_held+0xb0/0xb0
>  __x64_sys_getsockopt+0xba/0x150
>  ? syscall_enter_from_user_mode+0x1d/0x50
>  do_syscall_64+0x33/0x40
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
>
> Fixes: 0fc1a726f897 ("Bluetooth: sco: new getsockopt options BT_SNDMTU/BT_RCVMTU")
> Reported-by: Hulk Robot <hulkci@...wei.com>
> Signed-off-by: Wei Yongjun <weiyongjun1@...wei.com>

Reviewed-by: Luiz Augusto Von Dentz <luiz.von.dentz@...el.com>

>
> diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c
> index 79ffcdef0b7a..22a110f37abc 100644
> --- a/net/bluetooth/sco.c
> +++ b/net/bluetooth/sco.c
> @@ -1003,6 +1003,11 @@ static int sco_sock_getsockopt(struct socket *sock, int level, int optname,
>
>         case BT_SNDMTU:
>         case BT_RCVMTU:
> +               if (sk->sk_state != BT_CONNECTED) {
> +                       err = -ENOTCONN;
> +                       break;
> +               }
> +
>                 if (put_user(sco_pi(sk)->conn->mtu, (u32 __user *)optval))
>                         err = -EFAULT;
>                 break;
> --
> 2.25.1
>


-- 
Luiz Augusto von Dentz