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

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Message-ID: <20200413220813.zfft3e44kqnehlrh@ast-mbp.dhcp.thefacebook.com>
Date:   Mon, 13 Apr 2020 15:08:13 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     David Ahern <dsahern@...nel.org>
Cc:     daniel@...earbox.net, ast@...nel.org, netdev@...r.kernel.org,
        David Ahern <dsahern@...il.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>
Subject: Re: [PATCH bpf] xdp: Reset prog in dev_change_xdp_fd when fd is
 negative

On Sun, Apr 12, 2020 at 07:32:04AM -0600, David Ahern wrote:
> 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>

Argh. Thanks for the fix.

Toke, please review.