From: Eduard Zingerman <eddyz87@gmail.com>
To: Amery Hung <ameryhung@gmail.com>, bpf@vger.kernel.org
Cc: daniel@iogearbox.net, andrii@kernel.org,
alexei.starovoitov@gmail.com, martin.lau@kernel.org,
kernel-team@meta.com
Subject: Re: [PATCH bpf-next v1 1/2] bpf: Do not allow tail call in strcut_ops program with __ref argument
Date: Thu, 20 Feb 2025 16:08:36 -0800 [thread overview]
Message-ID: <b64dfd940e7ee594332832e0e522e38e0c94724d.camel@gmail.com> (raw)
In-Reply-To: <20250220221532.1079331-1-ameryhung@gmail.com>
On Thu, 2025-02-20 at 14:15 -0800, Amery Hung wrote:
> Reject struct_ops programs with refcounted kptr arguments (arguments
> tagged with __ref suffix) that tail call. Once a refcounted kptr is
> passed to a struct_ops program from the kernel, it can be freed or
> xchged into maps. As there is no guarantee a callee can get the same
> valid refcounted kptr in the ctx, we cannot allow such usage.
>
> Signed-off-by: Amery Hung <ameryhung@gmail.com>
> ---
An alternative location for this check would be in the
check_helper_call(). If done there, this would allow dead code
elimination for tail calls within functions with refcounted arguments.
Which would be useful only if in the future tail calls from such
functions would be allowed (e.g. a program having a branch w/o tail
call for old kernel and with tail call for new kernel).
Probably unlikely to happen, so I think current position of the check is ok.
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
[...]
next prev parent reply other threads:[~2025-02-21 0:08 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-20 22:15 [PATCH bpf-next v1 1/2] bpf: Do not allow tail call in strcut_ops program with __ref argument Amery Hung
2025-02-20 22:15 ` [PATCH bpf-next v1 2/2] selftests/bpf: Test struct_ops program with __ref arg calling bpf_tail_call Amery Hung
2025-02-21 0:50 ` Eduard Zingerman
2025-02-21 0:08 ` Eduard Zingerman [this message]
2025-02-21 2:50 ` [PATCH bpf-next v1 1/2] bpf: Do not allow tail call in strcut_ops program with __ref argument patchwork-bot+netdevbpf
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