netdev - Re: [syzbot] [bpf?] [net?] general protection fault in dev_map

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Date: Thu, 28 Mar 2024 21:39:48 +0100
From: Toke Høiland-Jørgensen <toke@...nel.org>
To: Jesper Dangaard Brouer <hawk@...nel.org>, Alexei Starovoitov
 <alexei.starovoitov@...il.com>, syzbot
 <syzbot+af9492708df9797198d6@...kaller.appspotmail.com>
Cc: andrii@...nel.org, ast@...nel.org, bpf@...r.kernel.org,
 daniel@...earbox.net, davem@...emloft.net, eddyz87@...il.com,
 haoluo@...gle.com, john.fastabend@...il.com, jolsa@...nel.org,
 kpsingh@...nel.org, kuba@...nel.org, linux-kernel@...r.kernel.org,
 martin.lau@...ux.dev, netdev@...r.kernel.org, sdf@...gle.com,
 song@...nel.org, syzkaller-bugs@...glegroups.com, yonghong.song@...ux.dev
Subject: Re: [syzbot] [bpf?] [net?] general protection fault in dev_map_enqueue

Jesper Dangaard Brouer <hawk@...nel.org> writes:

> On 27/03/2024 16.19, Alexei Starovoitov wrote:
>> Toke, Jesper,
>> 
>> please take a look.
>> It's reproducible 100% of the time.
>> dst is NULL in dev_map_enqueue().
>> 
>
> The `dst` (NULL) is basically `ri->tgt_value` being passed through
> (unmodified) via xdp_do_redirect_frame() and __xdp_do_redirect_frame()
> into dev_map_enqueue().
>
> I think something is wrong in xdp_test_run_batch().
> The `ri->tgt_value` is being set in __bpf_xdp_redirect_map(), but I
> cannot see __bpf_xdp_redirect_map() being used in xdp_test_run_batch().
>
> Toke, can you take a look at xdp_test_run_batch() and where
> `ri->tgt_value` is getting set?

Sure! I'm off for Easter, but I'll take a look when I get back next week :)

-Toke