netdev - Re: [PATCH bpf] xdp: Reset prog in dev_change_xdp

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Message-ID: <87imi2pmcz.fsf@toke.dk>
Date:   Tue, 14 Apr 2020 09:17:32 +0200
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     David Ahern <dsahern@...nel.org>, daniel@...earbox.net,
        ast@...nel.org
Cc:     netdev@...r.kernel.org, David Ahern <dsahern@...il.com>
Subject: Re: [PATCH bpf] xdp: Reset prog in dev_change_xdp_fd when fd is negative

David Ahern <dsahern@...nel.org> writes:

> From: David Ahern <dsahern@...il.com>
>
> The commit mentioned in the Fixes tag reuses the local prog variable
> when looking up an expected_fd. The variable is not reset when fd < 0
> causing a detach with the expected_fd set to actually call
> dev_xdp_install for the existing program. The end result is that the
> detach does not happen.
>
> Fixes: 92234c8f15c8 ("xdp: Support specifying expected existing program when attaching XDP")
> Signed-off-by: David Ahern <dsahern@...il.com>
> Cc: Toke Høiland-Jørgensen <toke@...hat.com>

Ugh, my bad (obviously!). Thanks for the fix! I'll send an update to the
selftest to catch errors like this...

Reviewed-by: Toke Høiland-Jørgensen <toke@...hat.com>