From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Yonghong Song <yhs@fb.com>
Cc: "Alexei Starovoitov" <ast@kernel.org>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Martin KaFai Lau" <kafai@fb.com>,
"Song Liu" <songliubraving@fb.com>,
"Andrii Nakryiko" <andriin@fb.com>,
netdev@vger.kernel.org, bpf@vger.kernel.org,
linux-kernel@vger.kernel.org,
"Maciej Żenczykowski" <maze@google.com>,
"John Stultz" <john.stultz@linaro.org>,
"Alexander Potapenko" <glider@google.com>,
"Alistair Delva" <adelva@google.com>
Subject: Re: [PATCH] bpf: explicitly memset the bpf_attr structure
Date: Fri, 20 Mar 2020 16:46:33 +0100 [thread overview]
Message-ID: <20200320154633.GB765793@kroah.com> (raw)
In-Reply-To: <d0dfc2ff-8323-12ed-3c7e-e8c6a118b890@fb.com>
On Fri, Mar 20, 2020 at 08:23:57AM -0700, Yonghong Song wrote:
>
>
> On 3/20/20 2:48 AM, Greg Kroah-Hartman wrote:
> > For the bpf syscall, we are relying on the compiler to properly zero out
> > the bpf_attr union that we copy userspace data into. Unfortunately that
> > doesn't always work properly, padding and other oddities might not be
> > correctly zeroed, and in some tests odd things have been found when the
> > stack is pre-initialized to other values.
>
> Maybe add more contexts about the failure itself so it could be clear
> why we need this patch.
I didn't have the full details, I think Maciej has them though.
> As far as I know from the link below, the failure happens in
> CHECK_ATTR() which checks any unused *area* for a particular subcommand
> must be 0, and this patch tries to provide this guarantee beyond
> area beyond min(uattr_size, sizeof(attr)).
That macro also will get tripped up if padding is not zeroed out as
well, so this is good to fix up.
thanks for the review.
greg k-h
next prev parent reply other threads:[~2020-03-20 15:46 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-20 9:48 [PATCH] bpf: explicitly memset the bpf_attr structure Greg Kroah-Hartman
2020-03-20 15:23 ` Yonghong Song
2020-03-20 15:46 ` Greg Kroah-Hartman [this message]
2020-03-20 15:24 ` Daniel Borkmann
2020-03-20 15:31 ` Yonghong Song
2020-03-20 15:45 ` Greg Kroah-Hartman
2020-03-20 16:04 ` Daniel Borkmann
2020-03-20 16:15 ` Greg Kroah-Hartman
2020-03-20 16:22 ` [PATCH] bpf: explicitly memset some bpf info structures declared on the stack Greg Kroah-Hartman
2020-03-20 18:34 ` Yonghong Song
2020-03-20 20:07 ` Daniel Borkmann
2020-03-20 20:07 ` [PATCH] bpf: explicitly memset the bpf_attr structure Daniel Borkmann
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