linux-kernel - Re: [PATCH] bpf: add missing NULL check for __dev_get_by

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Message-ID: <CAADnVQJXH7M0uhsswbWq1RjNv-h5e2M_6AtWd-1TazBo+QTgUg@mail.gmail.com>
Date: Sun, 9 Mar 2025 11:00:15 +0100
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Qasim Ijaz <qasdev00@...il.com>
Cc: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, Eddy Z <eddyz87@...il.com>, 
	Song Liu <song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>, 
	John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, 
	Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
	bpf <bpf@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] bpf: add missing NULL check for __dev_get_by_index

On Sat, Mar 8, 2025 at 10:56 PM Qasim Ijaz <qasdev00@...il.com> wrote:
>
> The __dev_get_by_index function can return NULL if it fails to
> find a device with the provided ifindex.
>
> We should handle this case by adding a NULL check
> and cleaning up if it does happened.
>
> Signed-off-by: Qasim Ijaz <qasdev00@...il.com>
> Fixes: a38845729ea3 ("bpf: offload: add map offload infrastructure")
> ---
>  kernel/bpf/offload.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/kernel/bpf/offload.c b/kernel/bpf/offload.c
> index a10153c3be2d..28a30fa4457a 100644
> --- a/kernel/bpf/offload.c
> +++ b/kernel/bpf/offload.c
> @@ -530,6 +530,12 @@ struct bpf_map *bpf_map_offload_map_alloc(union bpf_attr *attr)
>         bpf_map_init_from_attr(&offmap->map, attr);
>         rtnl_lock();
>         offmap->netdev = __dev_get_by_index(net, attr->map_ifindex);
> +       if (!offmap->netdev) {
> +               rtnl_unlock();
> +               bpf_map_area_free(offmap);
> +               return ERR_PTR(-ENODEV);
> +       }

1. you're using some old git tree.
there is no such code in bpf_map_offload_map_alloc().

2. The actual code has bpf_dev_offload_check(offmap->netdev)
that does the NULL check already.

pw-bot: cr

> +
>         netdev_lock_ops(offmap->netdev);
>         down_write(&bpf_devs_lock);
>         err = bpf_dev_offload_check(offmap->netdev);
> --
> 2.39.5
>