netdev - Re: [PATCH net v2] xdp: xdp_mem_allocator can be NULL in trace_mem

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Date:   Wed, 09 Mar 2022 22:52:14 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        "David S. Miller" <davem@...emloft.net>,
        Ingo Molnar <mingo@...hat.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Yonghong Song <yhs@...com>
Subject: Re: [PATCH net v2] xdp: xdp_mem_allocator can be NULL in
 trace_mem_connect().

Sebastian Andrzej Siewior <bigeasy@...utronix.de> writes:

> Since the commit mentioned below __xdp_reg_mem_model() can return a NULL
> pointer. This pointer is dereferenced in trace_mem_connect() which leads
> to segfault.
>
> The trace points (mem_connect + mem_disconnect) were put in place to
> pair connect/disconnect using the IDs. The ID is only assigned if
> __xdp_reg_mem_model() does not return NULL. That connect trace point is
> of no use if there is no ID.
>
> Skip that connect trace point if xdp_alloc is NULL.
>
> [ Toke Høiland-Jørgensen delivered the reasoning for skipping the trace
>   point ]
>
> Fixes: 4a48ef70b93b8 ("xdp: Allow registering memory model without rxq reference")
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>

With Steven's fix:

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