From: Daniel Borkmann <daniel@iogearbox.net>
To: John Fastabend <john.fastabend@gmail.com>,
jolsa@kernel.org, andrii.nakryiko@gmail.com, ast@kernel.org
Cc: netdev@vger.kernel.org, bpf@vger.kernel.org
Subject: Re: [bpf PATCH] bpf: Do not allow btf_ctx_access with __int128 types
Date: Thu, 25 Jun 2020 17:01:40 +0200 [thread overview]
Message-ID: <d53db444-8473-a48c-179f-4baf13a97674@iogearbox.net> (raw)
In-Reply-To: <159303723962.11287.13309537171132420717.stgit@john-Precision-5820-Tower>
On 6/25/20 12:20 AM, John Fastabend wrote:
> To ensure btf_ctx_access() is safe the verifier checks that the BTF
> arg type is an int, enum, or pointer. When the function does the
> BTF arg lookup it uses the calculation 'arg = off / 8' using the
> fact that registers are 8B. This requires that the first arg is
> in the first reg, the second in the second, and so on. However,
> for __int128 the arg will consume two registers by default LLVM
> implementation. So this will cause the arg layout assumed by the
> 'arg = off / 8' calculation to be incorrect.
>
> Because __int128 is uncommon this patch applies the easiest fix and
> will force int types to be sizeof(u64) or smaller so that they will
> fit in a single register.
>
> v2: remove unneeded parens per Andrii's feedback
>
> Fixes: 9e15db66136a1 ("bpf: Implement accurate raw_tp context access via BTF")
> Acked-by: Andrii Nakryiko <andriin@fb.com>
> Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Applied, thanks!
next prev parent reply other threads:[~2020-06-25 15:01 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-24 22:20 [bpf PATCH] bpf: Do not allow btf_ctx_access with __int128 types John Fastabend
2020-06-25 15:01 ` Daniel Borkmann [this message]
-- strict thread matches above, loose matches on Subject: below --
2020-06-23 17:13 [bpf PATCH] bpf: do " John Fastabend
2020-06-23 18:33 ` Andrii Nakryiko
2020-06-24 22:23 ` John Fastabend
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