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Date:   Mon, 28 Sep 2020 21:25:05 +0200
From:   Daniel Borkmann <>
To:     Magnus Karlsson <>,,,,,
Subject: Re: [PATCH bpf-next] xsk: fix possible crash in socket_release when

On 9/26/20 11:26 AM, Magnus Karlsson wrote:
> From: Magnus Karlsson <>
> Fix possible crash in socket_release when an out-of-memory error has
> occurred in the bind call. If a socket using the XDP_SHARED_UMEM flag
> encountered an error in xp_create_and_assign_umem, the bind code
> jumped to the exit routine but erroneously forgot to set the err value
> before jumping. This meant that the exit routine thought the setup
> went well and set the state of the socket to XSK_BOUND. The xsk socket
> release code will then, at application exit, think that this is a
> properly setup socket, when it is not, leading to a crash when all
> fields in the socket have in fact not been initialized properly. Fix
> this by setting the err variable in xsk_bind so that the socket is not
> set to XSK_BOUND which leads to the clean-up in xsk_release not being
> triggered.
> Signed-off-by: Magnus Karlsson <>
> Reported-by:
> Fixes: 1c1efc2af158 ("xsk: Create and free buffer pool independently from umem")

Looks good either way, applied, thanks!

> I have not been able to reproduce this issue using the syzkaller
> config and reproducer, so I cannot guarantee it fixes it. But this bug
> is real and it is triggered by an out-of-memory in
> xp_create_and_assign_umem, just like syzcaller injects, and would lead
> to the same crash in dev_hold in xsk_release.

You can just asked syzbot (which I just did on the original report) via:

#syz test: git:// master


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