netdev - Re: [PATCH] can: raw: raw_getsockopt(): reduce scope of err

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Date: Tue, 20 Feb 2024 09:25:58 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Marc Kleine-Budde <mkl@...gutronix.de>
Cc: Oliver Hartkopp <socketcan@...tkopp.net>, "David S. Miller" <davem@...emloft.net>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, linux-can@...r.kernel.org, 
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] can: raw: raw_getsockopt(): reduce scope of err

On Tue, Feb 20, 2024 at 9:16 AM Marc Kleine-Budde <mkl@...gutronix.de> wrote:
>
> Reduce the scope of the variable "err" to the individual cases. This
> is to avoid the mistake of setting "err" in the mistaken belief that
> it will be evaluated later.
>
> Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
> ---
>  net/can/raw.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/net/can/raw.c b/net/can/raw.c
> index 897ffc17d850..2bb3eab98af0 100644
> --- a/net/can/raw.c
> +++ b/net/can/raw.c
> @@ -756,7 +756,6 @@ static int raw_getsockopt(struct socket *sock, int level, int optname,
>         struct raw_sock *ro = raw_sk(sk);
>         int len;
>         void *val;
> -       int err = 0;
>
>         if (level != SOL_CAN_RAW)
>                 return -EINVAL;
> @@ -766,7 +765,9 @@ static int raw_getsockopt(struct socket *sock, int level, int optname,
>                 return -EINVAL;
>
>         switch (optname) {
> -       case CAN_RAW_FILTER:
> +       case CAN_RAW_FILTER: {
> +               int err = 0;
> +
>                 lock_sock(sk);
>                 if (ro->count > 0) {
>                         int fsize = ro->count * sizeof(struct can_filter);
> @@ -791,7 +792,7 @@ static int raw_getsockopt(struct socket *sock, int level, int optname,
>                 if (!err)
>                         err = put_user(len, optlen);
>                 return err;
> -
> +       }
>         case CAN_RAW_ERR_FILTER:
>                 if (len > sizeof(can_err_mask_t))
>                         len = sizeof(can_err_mask_t);
> @@ -822,7 +823,9 @@ static int raw_getsockopt(struct socket *sock, int level, int optname,
>                 val = &ro->xl_frames;
>                 break;
>
> -       case CAN_RAW_XL_VCID_OPTS:
> +       case CAN_RAW_XL_VCID_OPTS: {
> +               int err = 0;
> +
>                 /* user space buffer to small for VCID opts? */
>                 if (len < sizeof(ro->raw_vcid_opts)) {
>                         /* return -ERANGE and needed space in optlen */
> @@ -839,6 +842,7 @@ static int raw_getsockopt(struct socket *sock, int level, int optname,
>                         err = put_user(len, optlen);
>                 return err;
>
> +       }
>         case CAN_RAW_JOIN_FILTERS:
>                 if (len > sizeof(int))
>                         len = sizeof(int);
>
> ---
> base-commit: c8fba5d6df5e476aa791db4f1f014dad2bb5e904
> change-id: 20240220-raw-setsockopt-f6e173cdbbbb

What is the target tree ?

In net-next tree, syzbot complained about a bug added in

commit c83c22ec1493c0b7cc77327bedbd387e295872b6
Author: Oliver Hartkopp <socketcan@...tkopp.net>
Date:   Mon Feb 12 22:35:50 2024 +0100

    can: canxl: add virtual CAN network identifier support

Patch to fix the issue has not been sent yet ?

diff --git a/net/can/raw.c b/net/can/raw.c
index cb8e6f788af84ac65830399baac6d1cf3d093e08..897ffc17d850670003e5cf3402477e8fc201f61e
100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -835,7 +835,9 @@ static int raw_getsockopt(struct socket *sock, int
level, int optname,
                        if (copy_to_user(optval, &ro->raw_vcid_opts, len))
                                err = -EFAULT;
                }
-               break;
+               if (!err)
+                       err = put_user(len, optlen);
+               return err;

        case CAN_RAW_JOIN_FILTERS:
                if (len > sizeof(int))