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From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>,
	Alexei Starovoitov <ast@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>, Zi Shen Lim <zlim.lnx@gmail.com>,
	Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
	Yonghong Song <yhs@fb.com>, Andrii Nakryiko <andriin@fb.com>,
	John Fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@chromium.org>,
	Jean-Philippe Brucker <jean-philippe@linaro.org>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	bpf <bpf@vger.kernel.org>,
	"Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Subject: Re: [PATCH bpf-next 0/1] arm64: Add BPF exception tables
Date: Fri, 18 Jun 2021 09:34:10 -0700	[thread overview]
Message-ID: <CAADnVQJux+8n-vpuK9FqTLuj4cXrp04pGkpvKaUdAPXLQ4c-PQ@mail.gmail.com> (raw)
In-Reply-To: <fedff32f-e511-a191-22b0-bf421bdcce2a@linux.ibm.com>

On Wed, Jun 16, 2021 at 11:58 PM Ravi Bangoria
<ravi.bangoria@linux.ibm.com> wrote:
>
>    $ dmesg
>    [  166.864325] BUG: unable to handle page fault for address: 0000000000d12345
>    [  166.864336] #PF: supervisor read access in kernel mode
>    [  166.864338] #PF: error_code(0x0000) - not-present page
>
> 0xd12345 is unallocated userspace address. Similarly, I also tried with

that's unfortunately expected, since this is a user address.

> p->dte = (void *)0xffffffffc1234567 after confirming it's not allocated
> to kernel or any module address. I see the same failure with it too.

This one is surprising though. Sounds like a bug in exception table
construction. Can you debug it to see what's causing it?
First check that do_kern_addr_fault() is invoked in this case.
And then fixup_exception() and why search_bpf_extables()
cannot find it.
Separately we probably need to replace the NULL check
with addr >= TASK_SIZE_MAX to close this issue though it's a bit artificial.

  reply	other threads:[~2021-06-18 16:34 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-28 15:21 [PATCH bpf-next 0/1] arm64: Add BPF exception tables Jean-Philippe Brucker
2020-07-28 15:21 ` [PATCH bpf-next 1/1] arm64: bpf: " Jean-Philippe Brucker
2020-07-29 17:28   ` Song Liu
2020-07-29 21:29     ` Daniel Borkmann
2020-07-30  8:28       ` Jean-Philippe Brucker
2020-07-30 12:28   ` Qian Cai
2020-07-30 14:22     ` Jean-Philippe Brucker
2020-07-30 19:47       ` Daniel Borkmann
2020-07-30 21:14         ` Jean-Philippe Brucker
2020-07-30 22:45           ` Daniel Borkmann
2021-06-09 12:04 ` [PATCH bpf-next 0/1] arm64: " Ravi Bangoria
2021-06-11  0:12   ` Alexei Starovoitov
2021-06-17  6:58     ` Ravi Bangoria
2021-06-18 16:34       ` Alexei Starovoitov [this message]
2021-06-22  7:10         ` Ravi Bangoria
2021-06-22 11:00         ` [PATCH] x86 bpf: Fix extable offset calculation Ravi Bangoria
2021-06-25  4:01           ` Alexei Starovoitov
2021-06-25  6:22             ` Ravi Bangoria
2021-06-25 15:07               ` Alexei Starovoitov

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