linux-kernel - Re: [PATCH net] net: validate SO_TXTIME clockid coming from userspace

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Date: Wed, 29 May 2024 09:58:32 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Abhishek Chauhan <quic_abchauha@...cinc.com>, 
 "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, 
 netdev@...r.kernel.org, 
 linux-kernel@...r.kernel.org, 
 Andrew Halaney <ahalaney@...hat.com>, 
 Willem de Bruijn <willemdebruijn.kernel@...il.com>, 
 Martin KaFai Lau <martin.lau@...nel.org>, 
 Martin KaFai Lau <martin.lau@...ux.dev>, 
 Daniel Borkmann <daniel@...earbox.net>, 
 bpf <bpf@...r.kernel.org>
Cc: kernel@...cinc.com, 
 syzbot+d7b227731ec589e7f4f0@...kaller.appspotmail.com, 
 syzbot+30a35a2e9c5067cc43fa@...kaller.appspotmail.com
Subject: Re: [PATCH net] net: validate SO_TXTIME clockid coming from 
 userspace

minor: double space before userspace

Abhishek Chauhan wrote:
> Currently there are no strict checks while setting SO_TXTIME
> from userspace. With the recent development in skb->tstamp_type
> clockid with unsupported clocks results in warn_on_once, which causes
> unnecessary aborts in some systems which enables panic on warns.
> 
> Add validation in setsockopt to support only CLOCK_REALTIME,
> CLOCK_MONOTONIC and CLOCK_TAI to be set from userspace.
> 
> Link: https://lore.kernel.org/netdev/bc037db4-58bb-4861-ac31-a361a93841d3@linux.dev/
> Link: https://lore.kernel.org/lkml/20240509211834.3235191-1-quic_abchauha@quicinc.com/

These discussions can be found directly from the referenced commit?
If any, I'd like to the conversation we had that arrived at this
approach.

> Fixes: 1693c5db6ab8 ("net: Add additional bit to support clockid_t timestamp type")
> Reported-by: syzbot+d7b227731ec589e7f4f0@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=d7b227731ec589e7f4f0
> Reported-by: syzbot+30a35a2e9c5067cc43fa@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=30a35a2e9c5067cc43fa
> Signed-off-by: Abhishek Chauhan <quic_abchauha@...cinc.com>
> ---
>  net/core/sock.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/net/core/sock.c b/net/core/sock.c
> index 8629f9aecf91..f8374be9d8c9 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -1083,6 +1083,17 @@ bool sockopt_capable(int cap)
>  }
>  EXPORT_SYMBOL(sockopt_capable);
>  
> +static int sockopt_validate_clockid(int value)

sock_txtime.clockid has type __kernel_clockid_t.

> +{
> +	switch (value) {
> +	case CLOCK_REALTIME:
> +	case CLOCK_MONOTONIC:
> +	case CLOCK_TAI:
> +		return 0;
> +	}
> +	return -EINVAL;
> +}
> +
>  /*
>   *	This is meant for all protocols to use and covers goings on
>   *	at the socket level. Everything here is generic.
> @@ -1497,6 +1508,11 @@ int sk_setsockopt(struct sock *sk, int level, int optname,
>  			ret = -EPERM;
>  			break;
>  		}
> +
> +		ret = sockopt_validate_clockid(sk_txtime.clockid);
> +		if (ret)
> +			break;
> +
>  		sock_valbool_flag(sk, SOCK_TXTIME, true);
>  		sk->sk_clockid = sk_txtime.clockid;
>  		sk->sk_txtime_deadline_mode =
> -- 
> 2.25.1
>